=Paper=
{{Paper
|id=Vol-1297/104-123_paper-17
|storemode=property
|title=Введение в анализ методов и средств поддержки научных экспериментов, движимых гипотезами
(Introduction into Analysis of Methods and Tools for Hypothesis-Driven Scientific Experiment Support)
|pdfUrl=https://ceur-ws.org/Vol-1297/104-123_paper-17.pdf
|volume=Vol-1297
|dblpUrl=https://dblp.org/rec/conf/rcdl/KalinichenkoKKM14
}}
==Введение в анализ методов и средств поддержки научных экспериментов, движимых гипотезами
(Introduction into Analysis of Methods and Tools for Hypothesis-Driven Scientific Experiment Support)
==
Introduction into Analysis of Methods and Tools
for Hypothesis-Driven Scientific Experiment Support
© Kalinichenko L.A. © Kovalev D.Y. © Kovaleva D.A. © Malkov O.Y.
Institute of Informatics Problems RAS Institute of Astronomy RAS
Moscow
leonidk@synth.ipi.ac.ru dm.kovalev@gmail.com dana@inasan.ru malkov@inasan.ru
Abstract prerequisite for discoveries in the 21st century. Data
Intensive Research (DIR) denotes a crosscut of DIS/IT
Data intensive sciences (DIS) are being areas aimed at the creation of effective data analysis
developed in frame of the new paradigm of technologies for DIS and other data intensive domains.
scientific study known as the Fourth paradigm,
Science endeavors to give a meaningful description
emphasizing an increasing role of
of the world of natural phenomena using what are
observational, experimental and computer
known as laws, hypotheses and theories. Hypotheses,
simulated data practically in all fields of
theories and laws in their essence have the same
scientific study. The principal goal of data
fundamental character (Fig. 1) [48].
intensive research (DIR) is an extraction
(inference) of knowledge from data. LAW THEORY
The intention of this work is to make an Which might Which might
overview of the existing approaches, methods become a become a
and infrastructures of the data analysis in DIR An Explanatory
An Generalizing A Prediction
accentuating the role of hypotheses in such Hypothesis
research process and efficient support of Hypothesis
hypothesis formation, evaluation and selection The Word
in course of the natural phenomena modeling
“Hypothesis”
and experiments carrying out. An introduction
Could Mean
into various concepts, methods and tools
intended for effective organization of Fig. 1. Multiple incarnations of hypotheses
hypothesis driven experiments in DIR is
A scientific hypothesis is a proposed explanation of
presented in the paper.
a phenomenon which still has to be rigorously tested. In
1 Hypotheses, theories, models and laws in contrast, a scientific theory has undergone extensive
testing and is generally accepted to be the accurate
data intensive science explanation behind an observation. A scientific law is a
Data intensive science (DIS) is being developed in proposition, which points out any such orderliness or
accordance with the 4th Paradigm [29] of scientific regularity in nature, the prevalence of an invariable
study (following three previous historical paradigms of association between a particular set of conditions and
the science development (empirical science, theoretical particular phenomena. In the exact sciences laws can
science, computational science)) emphasizing that often be expressed in the form of mathematical
science as a whole is becoming increasingly dependent relationships. Hypotheses explain laws, and well-tested,
on data as the core source for discovery. Emerging of corroborated hypotheses become theories (Fig. 1). At
the 4th Paradigm is motivated by the huge amounts of the same time the laws do not cease to be laws, just
data coming from scientific instruments, sensors, because they did not appear first as hypotheses and pass
simulations, as well as from people accumulating data through the stage of theories.
in Web or social nets. The basic objective of DIS is to Though theories and laws are different kinds of
infer knowledge from the integrated data organized in knowledge, actually they represent different forms of
networked infrastructures (such as warehouses, grids, the same knowledge construct. Laws are
clouds). At the same time, “Big Data” movement has generalizations, principles or patterns in nature, and
emerged as a recognition of the increased significance theories are the explanations of those generalizations.
of massive data in various domains. Open access to However, classification expressed at the Fig. 1 is
large volumes of data therefore becomes a key subjective. [40] provides examples showing that the
differences between laws, hypotheses and theories
Proceedings of the 16th All-Russian Conference "Digital consist only in that they stand at different levels in their
Libraries: Advanced Methods and Technologies, Digital claim for acceptance depending on how much empirical
Collections" ― RCDL-2014, Dubna, Russia, October evidence is amassed. Therefore there is no essential
13–16, 2014. difference between constructs used for expressing
104
hypotheses, theories and laws. Important role of In [52] the useful hypotheses of science are
hypotheses in scientific research can scarcely be considered to be of two kinds:
overestimated. In the edition of M. Poincaré's book [52] 1. The hypotheses which are
it is stressed that without hypotheses there is no science. valuable precisely because they are either verifiable or
Thus it is not surprising that so much attention in the else refutable through a definite appeal to the tests
scientific research and the respective publications is furnished by experience;
devoted to the methods for hypothesis manipulation in
2. The hypotheses which, despite the fact that
experimenting and modeling of various phenomena
experience suggests them, are valuable despite, or
applying the means of informatics. The idea that the
even because, of the fact that experience
new approaches are needed that can address both data
can neither confirm nor refute them.
driven and hypothesis driven sciences runs all through
this paper. Such symbiosis alongside with the Aspects of science which are determined by the use
hypothesis-driven tradition of science (‘‘first of the hypotheses of the second kind are considered in
hypothesize-then-experiment’’) might cause wide the M. Poincaré's book [52] as “constituting an essential
application of another one that is typified by ‘‘first human way of viewing nature, an interpretation rather
experiment-then-hypothesize’’ mode of research. Often than a portrayal or a prediction of the objective facts of
the “first experiment” ordering in DIS is motivated by nature, an adjustment of our conceptions of things to the
the necessity of analysis of the existing massive data to internal needs of our intelligence”. According to M.
generate a hypothesis. Poincaré's discussion, the central problem of the logic
of science becomes the problem of the relation between
Generalization the two fundamentally distinct kinds of hypotheses, i.e.,
Abduction between those which cannot be verified or refuted
(Law)
through experience, and those which can be empirically
Induction Deduction tested.
The analysis in this paper will be focused mostly on
the modeling of hypotheses of the first kind, leaving
Evidence (Facts) issues of analysis the relations between such two kinds
of hypotheses to further study.
Fig. 2 Enhanced knowledge production diagram
The rest of the paper is organized as follows.
In the course of our study paying attention to the Section 2 discusses the basic concepts defining the role
issue of inductive and deductive reasoning in hypothesis of hypotheses in the formation of scientific knowledge
driven sciences will be emphasized. On Fig. 2 such and the respective organization of the scientific
ways of knowledge production are shown [48]. experiments. Approaches for hypothesis formulation,
“Generalization” here means any subset of hypotheses, logical reasoning, hypothesis modeling and testing are
theories and laws and “Evidence” is any subset of all briefly introduced in Section 3. In Section 4 a general
facts accumulated in a specific DIS. overview of the basic facilities provided by informatics
All researchers collect and interpret empirical for the hypothesis driven experimentation scenarios,
evidence through the process called induction. This is a including conceptual modeling, simulations, statistics
technique by which individual pieces of evidence are and machine learning methods is given. Into Section 5
collected and examined until a law is discovered or a several examples of organization of hypothesis driven
theory is invented. Frances Bacon first formalized scientific experiments are included. Conclusion
induction [4]. The method of (naïve) induction (Fig. 2) summarizes the discussion.
he suggested is in part the principal way by which
humans traditionally have produced generalizations that 2 Role of hypotheses in scientific
permit predictions. The problem with induction is that it experiments: basic principles
is both impossible to collect all observations pertaining
to a given situation in all time – past, present and future. Normally, scientific hypotheses have the form of a
mathematical model. Sometimes one can also formulate
The formulation of a new law begins through
them as existential statements, stating that some
induction as facts are heaped upon other relevant facts.
particular instance of the phenomenon under
Deduction is useful in checking the validity of a law.
examination has some characteristic and causal
The Fig. 2 shows that a valid law would permit the
explanations, which have the general form of universal
accurate prediction of facts not yet known. Also an
statements, stating that every instance of the
abduction [49] is the process of validating a given
phenomenon has a particular characteristic (e.g., for
hypothesis through reasoning by successive
all x, if x is a swan, then x is white). Scientific
approximation. Under this principle, an explanation is
hypothesis considered as a declarative statement
valid if it is the best possible explanation of a set of
identifies the predicted relationship (associative or
known data. Abductive validation is common practice
causal) between two or more variables (independent and
in hypothesis formation in science. Hypothesis related
dependent). In causal relationship a change caused by
logic reasoning issues are considered in more details in
the independent variable is predicted in the dependent
section 3.
variable. Variables are more commonly related in non-
causal (associative) way [25].
105
In experimental studies the researcher manipulates falsification can be sudden and definitive. Einstein said:
the independent variable. The dependent variable is “No amount of experimentation can ever prove me
often referred to as consequence or the presumed effect right; a single experiment can prove me wrong”. To
that varies with a change of the independent variable. scientists and philosophers outside the Popperian belief
The dependent variable is not manipulated. It is [53], science operates mainly by induction
observed and assumed to vary with changes in the (confirmation), and also and less often by
independent variable. Predictions are made from the disconfirmation (falsification). Its language is almost
independent variable to the dependent variable. It is the always one of induction. For this survey both
dependent variable that the researcher is interested in philosophical treatment of hypotheses are acceptable.
understanding, explaining or predicting [25]. Sometimes such way of reasoning is called the
In case when a possible correlation or similar hypothetico-deductive method. According to it,
relation between variables is investigated (such as, e.g., scientific inquiry proceeds by formulating a hypothesis
whether a proposed medication is effective in treating a in a form that could conceivably be falsified by a test on
disease, that is, at least to some extent and for some observable data. A test that could and does run contrary
patients), a few cases in which the tested remedy shows to predictions of the hypothesis is taken as a
no effect do not falsify the hypothesis. Instead, falsification of the hypothesis. A test that could but does
statistical tests are used to determine how likely it is that not run contrary to the hypothesis corroborates the
the overall effect would be observed if no real relation theory.
as hypothesized exists. If that likelihood is sufficiently A scientific method involves experiment, to test the
small, the existence of a relation may be assumed. In ability of some hypothesis to adequately answer the
statistical hypothesis testing two hypotheses are question under investigation. A prediction enabled by
compared, which are called the null hypothesis and the hypothesis suggests a test (observation or experiment)
alternative hypothesis. The null hypothesis states that for the hypothesis thus becoming testable. If a
there is no relationship between the phenomena hypothesis does not generate any observational tests,
(variables) whose relation is under investigation, or at there is nothing that a scientist can do with it.
least not of the form given by the alternative hypothesis. For example, not testable hypothesis: "Our universe
The alternative hypothesis, as the name suggests, is the is surrounded by another, larger universe, with which
alternative to the null hypothesis: it states that there is we can have absolutely no contact"; not verifiable
some kind of relation. (though testable) hypothesis: "There are other inhabited
Alternative hypotheses are generally used more planets in the universe"; scientific hypothesis (both
often than null hypotheses because they are more testable and verifiable): "Any two objects dropped from
desirable to state the researcher’s expectations. But in the same height above the surface of the earth will hit
any study that involves statistical analysis the the ground at the same time, as long as air resistance
underlying null hypothesis is usually assumed [25]. It is is not a factor" (http://www.batesville.k12.in.us/physics/
important, that the conclusion “do not reject the null phynet/aboutscience/hypotheses.html).
hypothesis” does not necessarily mean that the null A problem (research question) should be formulated
hypothesis is true. It suggests that there is not sufficient as an issue of what relation exists between two or more
evidence against the null hypothesis in favor of the variables. The problem statement should be such as to
alternative hypothesis. Rejecting the null hypothesis imply possibilities of empirical testing otherwise this
suggests that the alternative hypothesis may be true. will not be a scientific problem. Problems and
Any useful hypothesis will enable predictions by hypotheses being generalized relational statements
reasoning (including deductive reasoning). It might enable to deduce specific empirical manifestations
predict the outcome of an experiment in a laboratory implied by the problem and hypotheses. In this process
setting or the observation of a phenomenon in nature. hypotheses can be deduced from theory and from other
The prediction may also invoke statistics assuming that hypotheses. A problem cannot be scientifically solved
a hypothesis must be falsifiable [53], and that one unless it is reduced to hypothesis form, because a
cannot regard a proposition or theory as scientific if it problem is not directly testable [37].
does not admit the possibility of being shown false. The Most formal hypotheses connect concepts by
way to demarcate between hypotheses is to call specifying the expected relationships between
scientific those for which we can specify (beforehand) propositions. When a set of hypotheses are grouped
one or more potential falsifiers as the respective together they become a type of conceptual framework.
experiments. Falsification was supposed to proceed When a conceptual framework is complex and
deductively instead of inductively. incorporates causality or explanation it is generally
Other philosophers of science have rejected the referred to as a theory [28]. In general, hypotheses have
criterion of falsifiability or supplemented it with other to reflect the multivariate complexity of the reality. A
criteria, such as verifiability (only statements about the scientific theory summarizes a hypothesis or a group of
world that are empirically confirmable or logically hypotheses that have been supported with repeated
necessary are cognitively meaningful). They claim that testing. A theory is valid as long as there is no evidence
science proceeds by "induction"— that is, by finding to dispute it. Scientific paradigm explains the working
confirming instances of a conjecture. Popper treated set of theories under which science operates.
confirmation as never certain [53]. However, a
106
Elements of hypothesis-driven research and their
relationships are shown on Fig. 3 [23, 57]. The
hypothesis triangle relations, explains, formulates,
Weak Galaxy Earth special location
represents are functional in the scientist's final decision in
lensing clustering
adopting a particular model m1 to formulate a hypothesis
h1, which is meant to explain phenomenon p1.
Dark Energy Non uniform universe
Fig. 4. A lattice theoretic representation for hypothesis
relationship
The hypothesis lattice is unfolded into model and
phenomena isomorphic lattices according to the
hypothesis triangle (Fig. 3) [23]. The lattices are
isomorphic if one takes subsets of M (Model), H
(Hypotheses) and P (Phenomenon) such that formulates,
explains and represents are both one-to-one and onto
mappings (i.e., bijections), seen as structure-preserving
Fig. 3. Elements of hypothesis-driven research mappings (morphisms). Example of the isomorphic
In [23] the lattice structure for hypothesis lattice is shown on the Fig. 5 [23]. This particular lattice
interconnection is proposed as shown on Fig. 4. A corresponds to the case in Computational
hypothesis lattice is formed by considering a set of Hemodynamics considered in [23]. Here model m1
hypotheses equipped with wasDerivedFrom as a strict formulates hypothesis h1, which explains phenomenon
order < (from the bottom to the top). Hypotheses p1. Similarly, m2 formulates h2, which explains p2, and
directly derived from exactly one hypothesis are atomic, so on. Properties of the hypothesis lattices and
while those directly derived from at least two operations over them are considered in [24].
hypotheses are complex.
h1. Mass h2. Incompressible h3. Momentum h4. Viscous h5. No
conversation fluid conservation fluid body forces
h6. blend(h1,h2) h7. blend(h3,h4,h5)
h8. blend(h6,h7)
m1. m2. m3. m4. m5.
explains
m6. m7.
m8.
p1. Mass p2. Fluid p3. Momentum p4. Fluid p5. Body
net flux compression net flux friction force effects
p6. Fluid p7. Fluid
divergence dynamics
p8. Fluid
behavior
Fig. 5. Hypothesis lattice unfolded into model and phenomenon isomorphic lattice
107
Models are one of the principal instruments of for phenomena, so additionally some criteria for
modern science. Models can perform two fundamentally choosing among different hypotheses are required.
different representational functions: a model can be a One way to implement abductive model of reasoning
representation of a selected part of the world, or a model is the abductive logic programming [36]. Hypothesis
can represent a theory in the sense that it interprets the generation in abduction logical framework is organized
laws and hypotheses of that theory. as follows. During the experiment, some new
Here we consider scientific models to be observations are encountered. Let B represents the
representations in both senses at the same time. One of background knowledge; O is the set of facts that
the most perplexing questions in connection with represents observations. Both B and O are logic
models is how they relate to theories. In this respect programs (set of rules in some rule language). In
models can be considered as a complement to theories, addition, Γ stands for a set of literals representing the set
as preliminary theories, can be used as substitutions of of abducibles, which are candidate assumptions to be
theories when the latter are too complicated to handle. added to B for explaining O. Given B, O and Γ, the
Learning about the model is done through experiments, hypothesis-generation problem is to find a set H of
thought experiments and simulation. Given a set of literals (called a hypothesis) such that: 1) B and H entail
parameters, a model can generate expectations about O, 2) B and H is consistent, and 3) H is some subset of
how the system will behave in a particular situation. A Г. If all conditions are met then H is an explanation of
model and the hypotheses it is based upon are supported O (with respect to B and Γ). Examples of abductive
when the model generates expectations that match the logic programming systems include ACLP [35], A-
behavior of its real-world counterpart. system [71], ABDUAL [2] and ProLogICA [59].
Abductive logic programming can also be implemented
A law generalizes a body of observations. Generally, by means of Answer Set Programming systems, e.g. by
a law represents a group of related undisputable the DLV system [14].
hypotheses using a handful of fundamental concepts and The example abductive logic program in ProLogICA
equations to define the rules governing a set of describes a simple model of the lactose metabolism of
phenomena. A law does not attempt to explain why the bacterium E.Coli [59]. The background knowledge
something happens – it simply states that it does. B describes that E. coli can feed on the sugar lactose if it
Facilities for support of the hypothesis-driven makes two enzymes permease and galactosidase. Like
experimentation will be discussed in the remaining all enzymes (E), these are made if they are coded by a
sections. gene (G) that is expressed. These enzymes are coded by
two genes (lac(y) and lac(z)) in cluster of genes (lac(X))
3 Hypothesis manipulation in scientific called an operon that is expressed when the amounts
(amt) of glucose are low and lactose are high or when
experiments they are both at medium level. The abducibles, Г,
declare all ground instances of the predicates "amount"
3.1 Hypothesis generation as assumable. This reflects the fact that in the model it is
Researchers that support rationality of scientific not known what are the amounts at any time of the
discovery presented several methods for hypothesis various substances. This is incomplete information that
generation, including discovery as abduction, induction, we want to find out in each problem case that we are
anomaly detection, heuristics programming and use of examining. The integrity constraints state that the
analogies [73]. amount of a substance (S) can only take one value.
Discovery as abduction characterizes reasoning ## Background Knowledge (B)
feed(lactose):-
processes that take place before a new hypothesis is make(permease),make(galactosidase).
justified. The abductive model of reasoning that leads to make(Enzyme):- code(Gene,Enzyme),express(Gene).
plausible hypotheses formulation is conceptualized as express(lac(X)):-
an inference beginning with data. According to [50] an amount(glucose,low),amount(lactose,hi).
express(lac(X)):-
abduction happens as follows: 1) Some phenomena p1, amount(glucose,medium),amount(lactose,medium).
p2, p3, … are encountered for which there is no or little code(lac(y),permease).
explanation; 2) However, p1, p2, p3, … would not be code(lac(z),galactosidase).
surprising if a hypothesis H were added. They would temperature(low):-amount(glucose,low).
false :- amount(S,V1), amount(S,V2), V1 != V2.
certainly follow from something like H and would be
explained by it; 3) Therefore there is good reason for ## Abducibles (Г)
elaborating an hypothesis H – for proposing it as a abducible_predicate(amount).
possible hypothesis from which the assumption p1, p2, ## Observation (O)
p3, … might follow. The abductive model of reasoning feed(lactose).
is primarily a process of explaining anomalies or
surprising phenomena [63]. The scientists' reasoning This goal generates two possible hypotheses:
{amount(lactose,hi), amount(glucose,low)}
proceeds abductively from an anomaly to an {amount(lactose,medium),amount(glucose,medium)}
explanatory hypothesis in light of which the phenomena
would no longer be surprising. There can be several Just a couple of another examples of real rule-based
different hypotheses that can serve as the explanations systems, where abductive logic programming is used.
108
Robot Scientist (see 4.4) abductively hypothesizes new reasoning with hypotheses, i.e., the propositions whose
facts about the yeast functional biology by inferring truth or falsity is uncertain.
what is missing from a model [38]. In [68], both Bayesian probability belongs to the category of
abduction and induction are used to formulate evidential probabilities; to evaluate the probability of a
hypotheses about inhibition in metabolic pathways. hypothesis, the Bayesian probabilist specifies some
Augmenting background knowledge is done with prior probability, which is then updated in the light of
abduction, after that induction is used for learning new, relevant data (evidence) [64]. The Bayesian
general rules. In [33] authors use SOLAR reasoning interpretation provides a standard set of procedures and
system to abductively generate hypotheses about the formulae to perform this calculation.
inhibitory effects of toxins on the rat metabolisms.
Hypothesis testing in classical statistic style. After
The process of discovery is deeply connected also
null and alternative hypotheses are stated, some
with the search of anomalies. There are a lot of methods
statistical assumptions about data samples should be
and algorithms to discover anomalies. Anomaly
done, e.g. assumptions about statistical independence or
detection is an important research problem in data
distributions of observations. Failing to provide correct
mining that aims to find objects that are considerably
assumptions leads to the invalid test results.
dissimilar, exceptional and inconsistent with respect to
the majority data in an input database [6]. A common problem in classical statistics is to ask
whether a given sample is consistent with some
Analogies play several roles in science. Not only do
hypothesis. For example, we might be interested in
they contribute to discovery but they also play a role in
whether a measured value xi, or the whole set {xi}, is
the development and evaluation of scientific theories
consistent with being drawn from a Gaussian
(new hypotheses) by analogical reasoning.
distribution N(μ,σ). Here N(μ,σ) is our null hypothesis.
3.2 Hypothesis evaluation It is always assumed that we know how to compute
the probability of a given outcome from the null
Being testable and falsifiable, a scientific hypothesis hypothesis: for example, given the cumulative
provides a solid basis to its further modeling and testing. distribution function, 0 ≤ H0(x) ≤ 1, the probability that
There are several ways to do it, including the use of we would get a value at least as large as xi is
statistics, machine learning and logic reasoning p(x > xi ) = 1 – H0(xi), and is called the p-value.
techniques. Typically, a threshold p value is adopted, called the
3.2.1 Statistical testing of hypotheses significance level α, and the null hypothesis is rejected
The classical (frequentist) and Bayesian statistic when p ≤ (e.g., if = 0.05 and p < 0.05, the null
approaches are applicable for hypothesis testing and hypothesis is rejected at a 0.05 significance level). If we
selection. Brief summary of the basic differences fail to reject a hypothesis, it does not mean that we
between these approaches are as follows [34]. proved its correctness because it may be that our sample
is simply not large enough to detect an effect.
Classical (frequentist) statistics is based on the
following beliefs: When performing these tests, we can meet with two
types of errors, which statisticians call Type I and Type
− Probabilities refer to relative frequencies of II errors. Type I errors are cases when the null
events. They are objective properties of the real world; hypothesis is true but incorrectly rejected. In the context
− Parameters of hypotheses (models) are fixed, of source detection, these errors represent spurious
unknown constants. Because they are not fluctuating, sources, or more generally, false positives (with respect
probability statements about parameters are to the alternative hypothesis). The false-positive
meaningless; probability when testing a single datum is limited by the
− Statistical procedures should have well-defined adopted significance level . Cases when the null
long-run frequency properties. hypothesis is false, but it is not rejected are called
In contrast, Bayesian approach takes the following Type II errors (missed sources, or false negatives (again,
assumptions: with respect to the alternative hypothesis)). The false-
negative probability when testing a single datum is
− Probability describes the degree of subjective usually called , and is related to the power of test as
belief, not the limiting frequency. Probability statements
(1 – ). Hypothesis testing is intimately related to
can be made about things other than data, including
comparisons of distributions.
hypotheses (models) themselves as well as their
parameters; As the significance level is decreased (the
criterion for rejecting the null hypothesis becomes more
− Inferences about a parameter are made by
conservative), the number of false positives decreases
producing its probability distribution — this distribution
and the number of false negatives increases. Therefore,
quantifies the uncertainty of our knowledge about that
there is a trade-off to be made to find an optimal value
parameter. Various point estimates, such as expectation
value, may then be readily extracted from this of , which depends on the relative importance of false
distribution. negatives and positives in a particular problem. Both the
acceptance of false hypotheses and the rejection of true
The Bayesian interpretation of probability can be ones are errors that scientists should try to avoid. There
seen as an extension of propositional logic that enables is discussion as to what states of affairs is less desirable;
109
many people think that the acceptance of a false The question often arises as to which is the ‘best’
hypothesis is always worse than failure to accept a true model (hypothesis) to use; ‘model selection’ is a
one and that science should in the first place try to avoid technique that can be used when we wish to
the former kind of error. discriminate between competing models (hypotheses)
When many instances of hypothesis testing are and identify the best model (hypothesis) in a set, {M1,
performed, a process called multiple hypothesis testing, the ..., Mn}, given the data.
fraction of false positives can significantly exceed the We need to remind the basic notation. The Bayes
value of . The fraction of false positives depends not only theorem can be applied to calculate the posterior
on and the number of data points, but also on the number probability p(Mj|d) for each model (or hypothesis) Mj
of true positives (the latter is proportional to the number of representing our state of knowledge about the truth of
instances when an alternative hypothesis is true). the model (hypothesis) in the light of the data d as
Depending on data type (discrete vs. continuous follows:
random variables) and what we can assume (or not) p(Mj|d) = p(d|Mj) p(Mj) / p(d),
about the underlying distributions, and the specific where p(Mj) is the prior belief in the model (hypothesis)
question we ask, we can use different statistical tests. that represents our state of knowledge (or ignorance)
The underlying idea of statistical tests is to use data to about the truth of the model (hypothesis) before we
compute an appropriate statistic, and then compare the have analyzed the current data, p(d|Mj) is the model
resulting data-based value to its expected distribution. (hypothesis) likelihood (represents the probability that
The expected distribution is evaluated by assuming that some data are produced under the assumption of this
the null hypothesis is true. When this expected model) and p(d) is a normalization constant given by:
p (d M ) p ( M ) .
distribution implies that the data-based value is unlikely
to have arisen from it by chance (i.e., the corresponding p(d) = i i
i
p value is small), the null hypothesis is rejected with The relative ‘goodness’ of models is given by a
some threshold probability , typically 0.05 or 0.01 comparison of their posterior probabilities, so to
(p < ). Note again that p > does not mean that the compare two models Ma and Mb, we look at the ratio of
hypothesis is proven to be correct. the model posterior probabilities:
The number of various statistical tests in the p(Ma|d) / p(Mb|d) = p(d|Ma) p(Ma) / p(d|Mb) p(Mb).
literature is overwhelming and their applicability is
The Bayes factor, Bab can be computed as the ratio
often hard to decide (see [19, 31] for variety of
of the model likelihoods:
statistical methods in SPSS). When the distributions are
not known, tests are called nonparametric, or Bab = p(d|Ma) / p(d|Mb).
distribution-free tests. The most popular nonparametric Empirical scale for evaluating the strength of
test is the Kolmogorov–Smirnov (K-S) test, which evidence from the Bayes factor Bij between two models
compares the cumulative distribution function, F (x), for is shown in Tabl. 1 [45].
two samples, {x1i }, i = 1, ..., N1 and {x2i }, i = 1, ..., N2.
Tabl. 1. Strength of evidence for Bayes factor Bij
The K-S test is not the only option for nonparametric for two models
comparison of distributions. The Cramér-von Mises
criterion, the Watson test, and the Anderson–Darling |ln Bij| Odds Strength of evidence
test are similar in spirit to the K-S test, but consider < 1.0 <3:1 Inconclusive
somewhat different statistics. The Mann–Whitney– 1.0 ~3:1 Weak evidence
Wilcoxon test (or the Wilcoxon rank-sum test) is a 2.5 ~ 12 : 1 Moderate evidence
nonparametric test for testing whether two data sets are 5.0 ~ 150 : 1 Strong evidence
drawn from distributions with different location
parameters (if these distributions are known to be The Bayes factor gives a measure of the ‘goodness’
Gaussian, the standard classical test is called the t test). of a model, regardless of the prior belief about the
A few standard statistical tests can be used when we model; the higher the Bayes factor, the better the model
know, or can assume, that both h(x) and f(x) are is. In many cases, the prior belief in each model in the
Gaussian distributions (e.g., the Anderson–Darling test, set of proposed models will be equal, so the Bayes
the Shapiro–Wilk test) [34]. More on statistical tests can factor will be equivalent to the ratio of the posterior
be found in [19, 31, 32, 34]. probabilities of the models. The ‘best’ model in the
Bayesian sense is the one which gives the best fit to the
Hypothesis (model) selection and testing in data with the smallest parameter space.
Bayesian style. The Bayesian approach can be thought A special case of model (hypothesis) selection is
of as formalizing the process of continually refining our Bayesian hypothesis testing [34, 62]. Taking M1 to be
state of knowledge about the world, beginning with no the “null” hypothesis, we can ask whether the data
data (as encoded by the prior), then updating that by supports the alternative hypothesis M2, i.e., whether we
multiplying in the likelihood once the data are observed can reject the null hypothesis. Taking equal priors
to obtain the posterior. When more data are taken, then p(M1) = p(M2), the odds ratio is
the posterior based on the first data set can be used as
the prior for the second analysis. Indeed, the data sets B21 = p(d|M1) / p(d|M2).
can be different.
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The inability to reject M1 in the absence of an a good inductive argument the premises should provide
alternative hypothesis is very different from the some degree of support for the conclusion, where such
hypothesis testing procedure in classical statistics. The support means that the truth of the premises indicates
latter procedure rejects the null hypothesis if it does not with some degree of strength that the conclusion is true.
provide a good description of the data, that is, when it is If the logic of good inductive arguments is to be of any
very unlikely that the given data could have been real value, the measure of support it articulates should
generated as prescribed by the null hypothesis. In meet the Criterion of Adequacy (CoA): as evidence
contrast, the Bayesian approach is based on the accumulates, the degree to which the collection of true
posterior rather than on the data likelihood, and cannot evidence statements comes to support a hypothesis, as
reject a hypothesis if there are no alternative measured by the logic, should tend to indicate that the
explanations for observed data [34]. hypotheses are probably false or probably true. In [27]
Comparing classical and Bayesian approaches [34], the extent to which a kind of logic based on the Bayes
it is rare for a mission-critical analysis be done in the theorem can estimate how the implications of
“fully Bayesian” manner, i.e., without the use of the hypotheses about evidence claims influences the degree
frequentist tools at the various stages. Philosophy and to which hypotheses are supported is discussed in detail.
beauty aside, the reliability and efficiency of the In particular, it is shown how such a logic may be
underlying computations required by the Bayesian applied to satisfy the CoA: as evidence accumulates,
framework are the main practical issues. A central false hypotheses will very probably come to have
technical issue at the heart of this is that it is much evidential support values (as measured by their
easier to do optimization (reliably and efficiently) in posterior probabilities) that approach 0; and as this
high dimensions than it is to do integration in high happens, a true hypothesis will very probably acquire
dimensions. Thus the usable machine learning methods, evidential support values (measured by their posterior
while there are ongoing efforts to adapt them to probabilities) that approach 1.
Bayesian framework, are almost all rooted in frequentist 3.2.3 Parameter estimation
methods.
Models (hypotheses) are typically described by
Most users of Bayesian estimation methods, in parameters θ whose values are to be estimated from
practice, are likely to use a mix of Bayesian and data. We describe this process according to [34]. For a
frequentist tools. The reverse is also true—frequentist particular model M and prior information I we get:
data analysts, even if they stay formally within the
frequentist framework, are often influenced by p(M, θ|d, I) = p(d|M, θ, I) p(M, θ|I) / p(d|I)
“Bayesian thinking,” referring to “priors” and The result p(M, θ|d, I) is called the posterior
“posteriors.” The most advisable position is probably to probability density function (pdf) for model M and
know both paradigms well, in order to make informed parameters θ, given data d and other prior information I.
judgments about which tools to apply in which This term is a (k + 1)-dimensional pdf in the space
situations [34]. More details on Bayesian style of spanned by k model parameters and the model M. The
hypothesis testing can be found in [34, 62, 64]. term p(d|M, θ, I) is the likelihood of data given some
3.2.2 Logic-based hypothesis testing model M and some fixed values of parameters θ
describing it, and all other prior information I. The term
According to the hypothetico-deductive approach
p(M, θ|I) is the a priori joint probability for model M
the hypotheses are tested by deducing predictions or
and its parameters θ in the absence of any of the data
other empirical consequences from general theories. If
used to compute likelihood, and is often simply called
these predictions are verified by experiments, this
the prior.
supports the hypothesis. It should be noted that not
anything that is logically entailed by a hypothesis can be In the Bayesian formalism, p(M, θ|d, I) corresponds
confirmed by a proper test for it. The relation between to the state of our knowledge (i.e., belief) about a model
hypothesis and evidence is often empirica l rather than and its parameters, given data d. To simplify the
logical. A clean deduction of empirical consequences notation, M(θ) will be substituted by M whenever the
from a hypothesis, as it may sometimes exist in physics, absence of explicit dependence on θ is not confusing. A
is practically inapplicable in biology. Thus, entailment completely Bayesian data analysis has the following
of the evidence by hypotheses under test is neither conceptual steps:
sufficient nor necessary for a good test. Inference to the 1. Formulation of the data likelihood p(d|M, I).
best explanation is usually construed as a form of 2. Choice of the prior p(θ|M,I), which incorporates
inductive inference (see abduction in 3.1) where a all other knowledge that might exist, but is not used
hypothesis’ explanatory credentials are taken to indicate when computing the likelihood (e.g., prior
its truth [72]. measurements of the same type, different
An inductive logic is a system of evidential support measurements, or simply an uninformative prior).
that extends deductive logic to less-than-certain Several methods for constructing "objective" priors
inferences. For valid deductive arguments the have been proposed. One of them is the principle of
premises logically entail the conclusion, where the maximum entropy for assigning uninformative priors by
entailment means that the truth of the premises provides maximizing the entropy over a suitable set of pdfs,
a guarantee of the truth of the conclusion. Similarly, in finding the distribution that is least informative (given
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the constraints). Entropy maximization with no testable accuracy and properties of the algorithms (such as, e.g.,
information takes place under a single constraint: the their convergence if they are iterative) are the issues to
sum of the probabilities must be one. Under this be investigated. Machine learning algorithms focus on
constraint, the maximum entropy for a discrete prediction, based on known properties learned from the
probability distribution is given by the uniform training data. Such machine learning algorithms as
distribution. decision tree, association rule, neural networks, support
3. Determination of the posterior p(M|d, I), using vector machines as well as other techniques of learning
Bayes theorem above. In practice, this step can be in Bayesian and probabilistic models [5, 26] are
computationally intensive for complex examples of the methods that belong to this second
multidimensional problems. culture.
4. The search for the best model M parameters, The models that best emulate the nature in terms of
which maximizes p(M|d, I), yielding the maximum a predictive accuracy are also the most complex and
posteriori (MAP) estimate. This point estimate is the inscrutable. Nature forms the outputs y from the inputs x
natural analog to the maximum likelihood estimate by means of a black box with complex and unknown
(MLE) from classical statistics. interior. Current accurate prediction methods are also
complex black boxes (such as neural nets, forests,
5. Quantification of uncertainty in parameter
support vectors). So we are facing two black boxes,
estimates, via credible regions. As in MLE, such an
where ours seems only slightly less inscrutable than
estimate can be obtained analytically by doing
nature’s [10]. In a choice between accuracy and
mathematical derivations specific to the chosen model.
interpretability, in applications people sometimes prefer
Also as in MLE, various numerical techniques can be
interpretability.
used to simulate samples from the posterior. This can be
viewed as an analogy to the frequentist approach, which However, the goal of a model is not interpretability
can simulate draws of samples from the true underlying (a way of getting information), but getting useful,
distribution of the data. In both cases, various accurate information about the relation between the
descriptive statistics can then be computed on such response and predictor variables. It is stated in [10] that
samples to examine the uncertainties surrounding the algorithmic models can give better predictive accuracy
data and estimators of model parameters based on that than formulaic models, providing also better
data. information about the underlying mechanism. And
actually this is what the goal of statistical analysis is.
6. Hypothesis testing as needed to make other
The researchers should be focused on solving the
conclusions about the model (hypothesis) or parameter
problems instead of asking what regression model they
estimates.
can create.
3.3 Algorithmic generation and evaluation An objection to this idea (expressed by Cox) is that
of hypotheses prediction without some understanding of underlying
process and linking with other sources of information
Two cultures of data analysis (formulaic modeling 1 becomes more and more tentative. Due to that it is
and algorithmic modeling) distinguished here in suggested to construct the stochastic calculation models
accordance with [10] can be applied to the hypothesis that summarize the understanding of the phenomena
extraction and generation based on data. under study. One of the objectives of such approach
Formulaic modeling is a process for estimating the might be an understanding and test of hypotheses about
relationships among variables. It includes many underlying process. Given the relatively small sample
techniques for modeling and analyzing several size following such direction could be productive. But
variables, when the focus is on the formulae y = f(x) data characteristics are rapidly changing. In many of the
that give a relation specifying a vector of dependent most interesting current problems, the idea of starting
variables y in terms of a vector of independent variables with a formal model is not tenable. The methods used in
x. In a statistics experiment (based on various regression statistics for small sample sizes and a small number of
techniques) the dependent variable defines the event variables are not applicable. Data analytics need to be
studied and is expected to change whenever the more pragmatic. Given a statistical problem, find a good
independent variable (predictor variables, extraneous solution, whether it is a formulaic model, an algorithmic
variables) is altered. Such methods as linear regression, model or a Bayesian model or a completely different
logistic regression, multiple regression are well-known approach.
examples of the representatives of this modeling In the context of the hypothesis driven analysis we
approach. should pay attention to the question how far can we go
In the algorithmic modeling culture the approach is applying the algorithmic modeling for hypothesis
to find an algorithm that operates on x to predict the generation and testing. Various approaches to machine
responses y. What is observed is a set of x’s that go in learning use related to hypothesis formation and
and a subsequent set of y’s that come out. Predictive selection can be found in [5, 10, 34].
Besides machine learning, an interesting example of
1
In [10] instead of “formulaic modeling” the term “data algorithmic generation of hypotheses can be found in
modeling” is used that looks misleading in the computer the IBM Watson project [18] where the symbiosis of the
science context. general-purpose reusable natural language processing
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(NLP) and knowledge representation and reasoning amount of observations nowadays available. The so-
(KRR) technologies (under the name DeepQA) is called ‘cosmological concordance model’ is based on
exploited for answering arbitrary questions over the the cosmological principle (i.e. the Universe is isotropic
existing natural language documents as well as and homogeneous, at least on large enough scales) and
structured data resources. Hypothesis generation takes on the hot big bang scenario, complemented by an
the results of question analysis and produces candidate inflationary epoch. This remarkably simple model is
answers by searching the available data sources and able to explain with only half a dozen free parameter
extracting answer-sized snippets from the search results. observations spanning a huge range of time and length-
Each candidate answer plugged back into the question is scales. Since both a cold dark matter (CDM) and a
considered a hypothesis, which the system has to prove cosmological constant (Λ) component are required to fit
correct with some degree of confidence. After merging, the data, the concordance model is often referred to as
the system must rank the hypotheses and estimate ‘the ΛCDM model’.
confidence based on their merged scores. A machine- Several different types of explanation are possible
learning approach adopted is based on running the for the apparent late time acceleration of the Universe,
system over a set of training questions with known including different classes of dark energy model such as
answers and training a model based on the scores. An ΛCDM, wCDM; theories of modified gravity; void
important consideration in dealing with NLP-based models or the back reaction [45]. The methodology of
scorers is that the features they produce may be quite Bayesian doubt which gives an absolute measure of the
sparse, and so accurate confidence estimation requires degree of goodness of a model has been applied to the
the application of confidence-weighted learning issue of whether the ΛCDM model should be doubted.
techniques [18] – a new class of online learning
The methodology of Bayesian doubt dictates that an
methods that maintain a probabilistic measure of
unknown idealized model X should be introduced
confidence in each parameter. It is important to note that
against which the other models may be compared.
instead of statistics based hypothesis testing, contextual
Following [67], ‘doubt’ may be defined as the posterior
evaluation of a wide range of loosely coupled
probability of the unknown model:
probabilistic question and semantic based content
analytics is applied for scoring different questions D ≡ p(X|d) = p(d|X) p(X) / p(d).
(hypotheses) and content interpretations. Training Here p(X) is the prior doubt, i.e. the prior on the
different models on different portions of the data in unknown model, which represents the degree of belief
parallel and combining the learned classifiers into a that the list of known models does not contain the true
single classifier allows to make the process applicable to model. The sum of all the model priors must be unity.
the large collections of data. More details on that can be The methodology of Bayesian doubt requires a
found in [17, 18] as well as in other Watson project baseline model (the best model in the set of known
related publications. models), for which in this application the ΛCDM has
been chosen. The average Bayes factor between ΛCDM
3.4 Bayesian motivation for discovery
and each of the known models is given by:
One way for discriminating between competing
B .
N
models of some phenomenon is to use Bayesian model ≡ 1/N i
i 1
selection approach (3.2.1), the Bayesian evidences for
The ratio R between the posterior doubt and prior
each of the proposed models (hypotheses) can be
doubt, which is called the relative change in doubt, is:
computed and the models can then be ranked by their
Bayesian evidence. This is a good method for R ≡ D/p(X).
identifying which is the best model in a given set of For doubt to grow, i.e. the posterior doubt to be
models, but it gives no indication of the absolute greater than the prior doubt (R << 1), the Bayes factor
goodness of the model. Bayesian model selection says between the unknown model X and the baseline model
nothing about the overall quality of the set of models must be much greater than the average Bayes factor:
(hypotheses) as a whole —the best model in the set may / BXΛ << 1.
merely be the best of in a set of poor models. Knowing
To genuinely doubt the baseline model, ΛCDM, it is
that the best model in the current set of models is not
not sufficient that R > 1, but additionally, the probability
particularly good model would provide motivation to
of ΛCDM must also decrease such that its posterior
search for a better model, and hence may lead to model
probability is greater than its prior probability, i.e.
discovery.
p(Λ|d) < p(Λ). We can define:
One way of assigning some measure of the absolute
RΛ ≡ p(Λ|d) / p(Λ).
goodness of a model is to use the concept of Bayesian
doubt, first introduced by [67]. Bayesian doubt works For ΛCDM to be doubted, the following two
by comparing all the known models in a set with an conditions must be fulfilled:
idealized model, which acts as a benchmark model. R > 1, RΛ < 1.
An application of the Bayesian doubt method for the If these two conditions are fulfilled, then it suggests
cosmological model building is given in [44, 45]. One that the set of known models is incomplete, and gives
of the most important questions in cosmology is to motivation to search for a better model not yet included,
identify the fundamental model underpinning the vast which may lead to model discovery.
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In [67] a way of computing an absolute upper bound In [54] the following elements related to hypothesis
for p(d|X) achievable among the class of known models driven science are conceptualized: a phenomenon
has been proposed. Finally it was found that current observed, a model interpreting this phenomenon, the
cosmic microwave background (CMB), matter power metadata defining the related computation together with
spectrum (mpk) and Type Ia supernovae (SNIa) the simulation definition (for simulation a declarative
observations.do not require the introduction of an logic-based language is proposed). Specific attention in
alternative model to the baseline ΛCDM model. The this work is devoted to hypothesis definition. The
upper bound of the Bayesian evidence for a presently explanation a scientific hypothesis conveys is a
unknown dark energy model against ΛCDM gives only relationship between the causal phenomena and the
weak evidence in favor of the unknown model. Since simulated one, namely, that the simulated phenomenon
this is an absolute upper bound, it was concluded that is caused by or produced under the conditions set by the
ΛCDM remains a sufficient phenomenological causal phenomena. By running the simulations defined
description of currently available observations. by the antecedents in the causal relationship, the
scientist aims at providing hypothetical analysis of the
4 Facilities for the scientific hypothesis- studied phenomenon.
driven experiment support Thus, the scientific hypothesis becomes an element
of the scientific model that may replace a phenomenon.
4.1 Conceptualization of scientific experiments When computing a simulation based on a scientific
hypothesis, i.e. according to the causal relationship it
DIS increasingly becomes dependent on establishes, the output results may be compared against
computational resources to aid complex researches. It phenomenon observations to assess the quality of the
becomes paramount to offer scientists mechanisms to hypothesis. Such interpretation provides for bridging the
manage the variety of knowledge produced during such gap between qualitative description of the phenomenon
investigations. Specific conceptual modeling facilities domain (scientific hypotheses may be used in
[54] are investigated to allow scientists to represent qualitative (i.e., ontological) assertions) and the
scientific hypotheses, models and associated corresponding quantitative valuation obtained through
computational or simulation interpretations which can simulations. According to the approach [54], complex
be compared against phenomena observations (Fig. 3). scientific models can be expressed as the composition of
The model allows scientists to record the existing computation models similarly to database views.
knowledge about an observable investigated
phenomenon, including a formal mathematical 4.2 Hypothesis space browsers
interpretation of it, if any. Model evolution and model
sharing need also to be supported taking either a In the HyBrow (Hypothesis Space Browser) project
mathematical or computational view (e.g., expressed by [58] the hypotheses for the biology domain are
scientific workflows). Declarative representation of represented as a set of first-order predicate calculus
scientific model allows scientists to concentrate on the sentences. In conjunction with an axiom set specified as
scientific issues to be investigated. Hypotheses can be rules that model known biological facts over the same
used also to bridge the gap between an ontological universe, and experimental data, the knowledge base
description of studied phenomena and the simulations. may contradict or validate some of the sentences in
Conceptual views on scientific domain entities allow for hypotheses, leaving the remaining ones as candidates
searching for definitions supporting scientific models for new discovery. As more experimental data is
sharing among different scientific groups. obtained and rules identified, discoveries become
positive facts or are contradicted. In the case of
In [23] the engineering of hypothesis as linked data
contradictions, the rules that caused the problems must
is addressed. A semantic view on scientific hypotheses
be identified and eliminated from the theory formed by
shows their existence apart from a particular statement
the hypotheses. In such model-theoretical approach, the
formulation in some mathematical framework. The
validation of hypotheses considers the satisfiability of
mathematical equation is considered as not enough to
the logical implications defined in the model with
identify the hypothesis, first because it must be
respect to an interpretation. This might be applicable
physically interpreted, second because there can be
also for simulation-based research, in which validation
many ways to formulate the same hypothesis. The link
is decided based on the quantitative analysis between
to a mathematical expression, however, brings to the
the simulation results and the observations [54].
hypothesis concept higher semantic precision. Another
HyBrow is based on an OWL ontology and application-
link, in addition, to an explicit description of the
level rules to contradict or validate hypothetical
explained phenomenon (emphasizing its “physical
statements. HyBrow provides for designing hypotheses,
interpretation") can bring forth the intended meaning.
and evaluating them for consistency with existing
By dealing with that hypothesis as a conceptual entity,
knowledge, uses an ontology of hypotheses to represent
the scientists make it possible to change its statement
hypotheses in machine understandable form as relations
formulation or even to assert a semantic mapping to
between objects (agents) and processes [65].
another incarnation of the hypothesis in case someone
else reformulates it. As an upgrade of HyBrow, the HyQue [12]
framework adopts linked data technologies and employs
Bio2RDF linked data to add to HyBrow semantic
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interoperability capabilities. HyBrow/HyQue's stored, or all the websites of tools relevant to
hypotheses are domain-specific statements that correlate Neuroscience. Annotation may be structured or
biological processes (seen as events) in the First-Order unstructured. Structured annotation means attaching a
Logic (FOL). Hypotheses are formulated as instances of Concept (tag or term) to an Assertion. Unstructured
the HyQue Hypothesis Ontology and are evaluated annotation means attaching free text. Concepts are
through a set of SPARQL queries against biologically- nodes in controlled vocabularies, which may also be
typed OWL and HyBrow data. The query results are hierarchical (taxonomies).
scored in terms of how the set of events correspond to
background expectations. A score indicates the level of 4.3 Scientific hypothesis formalization
support the data lends the hypothesis. Each event is An example showing on Fig. 6 the diversity of the
evaluated independently in order to quantify the degree components of a scientific hypothesis model has been
of support it provides for the hypothesis posed. borrowed from the applications in Neuroscience
Hypothesis scores are linked as properties to the [54, 55] and in a human cardiovascular system in
respective hypothesis. Computational Hemodynamics [23, 56]. The
OBI (the Ontology for Biomedical Investigations) formalization of a scientific hypothesis was provided by
project (http://obi-ontology.org) aims to model the a mathematical model, by a set of differential equations
design of an investigation: the protocols, the for continuous processes, quantifying the variations of
instrumentation, and materials used in experiments and physical quantities in continuous space-time and by the
the data generated [20]. Ontologies such as EXPO and mathematical solver (HEMOLAB) for discrete
OBI enable the recording of the whole structure of processes. The mathematical equations were represented
scientific investigations: how and why an investigation in MathML, enabling models interchange and reuse.
was executed, what conclusions were made, the basis In [3] the formalism of quantitative process models
for these conclusions, etc. As a result of these generic is presented that provides for encoding of scientific
ontology development efforts, the Minimum models formally as a set of equations and informally in
Information about a Genotyping Experiment (MIGen) terms of processes expressing those equations. The
recommends the use of terms defined in OBI. The use model revision works as follows. For input it is required
of a generic or a compliant ontology to supply terms an initial model; a set of constraints representing
will stimulate cross-disciplinary data-sharing and reuse. acceptable changes to the initial model in terms of
As much detail about an investigation as possible in processes; a set of generic processes that may be added
order to make the investigation more reproducible and to the initial model; observations to which the revised
reusable can be collected [39]. model should fit. These data provide the approach with
Hypothesis modeling is embedded into the a heuristic that guides search toward parts of the model
knowledge infrastructures being developed in various space that are consistent with the observations. The
branches of science. One example of such infrastructure algorithm generates a set of revised models that are
is considered under the name SWAN – a SemanticWeb sorted by their distance from the initial model and
Application in Neuromedicine [20]. SWAN is a project presented with their mean squared error on the training
for developing an integrated knowledge infrastructure data. The distance between a revised model and the
for the Alzheimer disease (AD) research community. initial model is defined as the number of processes that
SWAN incorporates the full biomedical research are present in one but not in the other. The abilities of
knowledge lifecycle in its ontological model, including the approach have been successfully checked in several
support for personal data organization, hypothesis environmental domains.
generation, experimentation, laboratory data Formalisms for hypothesis formation are mostly
organization, and digital pre-publication collaboration. monotonic and are considered to be not quite suitable
The common ontology is specified in an RDF Schema. for knowledge representation, especially in dealing with
SWAN’s content is intended to cover all stages of the incomplete knowledge, which is often the case with
“truth discovery” process in biomedical research, from respect to biochemical networks. In [69] knowledge
formulation of questions and hypotheses, to capture of based framework for the general problem of hypothesis
experimental data, sharing data with colleagues, and formation is presented. The framework has been
ultimately the full discovery and publication process. implemented by extending BioSigNet-RR – a
Several information categories created and managed knowledge based system that supports elaboration
in SWAN are defined as subclasses of Assertion. They tolerant representation and non-monotonic reasoning.
include Publication, Hypothesis, Claim, Concept, The main features of the extended system provide: (1)
Manuscript, DataSet, and Annotation. An Assertion seamless integration of hypothesis formation with
may be made upon any other Assertion, or upon any knowledge representation and reasoning; (2) use of
object specifiable by URL. For example, a scientist can various resources of biological data as well as human
make a Comment upon, or classify, the Hypothesis of expertise to intelligently generate hypotheses; (3)
another scientist. Linking to objects “outside” SWAN support for ranking hypotheses and for designing
by URL allows one to use SWAN as metadata to experiments to verify hypotheses. The extended system
organize – for example – all one’s PDFs of publications, is positioned as a prototype of an intelligent research
or the Excel files in which one’s laboratory data is assistant of molecular biologists.
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Fig. 6. Elements of the scientific hypothesis model
study functional genomics in the yeast Saccharomyces
4.4 Hypothesis-driven robots
cerevisiae, specifically to identify the genes encoding
The Robot Scientist [66] oriented on genomic 'locally orphan enzymes'. Adam uses a comprehensive
applications is a physically implemented system which logical model of yeast metabolism, coupled with a
is capable of running cycles of scientific bioinformatic database (Kyoto Encyclopaedia of Genes
experimentation and discovery in a fully automatic and Genomes – KEGG) and standard bioinformatics
manner: hypothesis formation, experiment selection to homology search techniques (PSI-BLAST and FASTA)
test these hypotheses, experiment execution using to hypothesize likely candidate genes that may encode
robotic system, results analysis and interpretation, the locally orphan enzymes. This hypothesis generation
repeating the cycle (closed-loop in which the results process is abductive.
obtained are used for learning from them and feeding To formalize Adam’s functional genomics
the resulting knowledge back into the experimental experiments, the LABORS ontology (LABoratory
models). Deduction, induction and abduction are types Ontology for Robot Scientists) has been developed.
of logical reasoning used in scientific discovery (section LABORS is a version of the ontology EXPO (as an
3). The full automation of science requires 'closed-loop upper layer ontology) customized for Robot scientists to
learning', where the computer not only analyses the describe biological knowledge. LABORS is expressed
results, but learns from them and feeds the resulting in OWL-DL. LABORS defines various structural
knowledge back into the next cycle of the process research units, e.g. trial, study, cycle of study and
(Fig. 6). replicate as well as design strategy, plate layout,
In the Robot Scientist the automated formation of expected actual results. The respective concepts and
hypotheses is based on the following key components: relations in the functional genomics data and metadata
1. Machine–computable representation of the are also defined. Both LABORS and the corresponding
domain knowledge. database (used for storing the instances of the classes)
are translated into Datalog in order to use the
2. Abductive or inductive inference of novel SWI-Prolog reasoner for required applications [39].
hypotheses.
There were two types of hypotheses generated. The
3. An algorithm for the selection of hypotheses. first level links an orphan enzyme, represented by its
4. Deduction of the experimental consequences of enzyme class (E.C.) number, to a gene (ORF) that
hypotheses. potentially encodes it. This relation is expressed as a two
Adam, the first Robot Scientist prototype, was place predicate where the first argument is the ORF and the
designed to carry out microbial growth experiments to
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second the E.C. number. An example of hypothesis at this based on graph theory and logical modeling makes it
level is: encodesORFtoEC('YBR166C', '1.1.1.25'). possible to keep an accurate track of all the result units
The second level of hypothesis involves the association used for different goals, while preserving the semantics
between a specific strain, referenced via the name of its of all the experimental entities involved in all the
missing ORF, and a chemical compound which should investigations. It is shown how experimentation and
affect the growth of the strain, if added as a nutrient to its machine learning are used to identify additional
environment. This level of hypothesis is derived from the knowledge to improve the metabolic model [13].
first by logical inference using a specific model of yeast
4.5 Hypotheses as data in probabilistic databases
metabolism. An example of such a hypothesis is: affects
growth('C00108','YBR166C'), where the first argument is Another view of hypotheses encoding and
the compound (names according to KEGG) and the second management is presented in [51]. Authors use
argument is the strain considered. probabilistic database techniques for hypotheses
Adam then designs the experimental assays required systematic construction and management. MayBMS
to test these hypotheses for execution on the laboratory [30], a probabilistic database management system, is
robotic system. These experiments are based on a two- used as a core for hypothesis management. This
factor design that compares multiple replicates of the methodology (called γ-DB) enables researchers to
strains with and without metabolites compared against maintain several hypotheses explaining some
wild type strain controls with and without metabolites. phenomena and provides evaluation mechanism based
on Bayesian approach to rank them.
System model and Initial START point: Experiment generation
knowledge base Hypotheses generation and design The construction of γ-DB database comprises
several steps. In the first step, phenomenon and
Execution of hypothesis entities are provided as input to the system.
Cycles of experiments on an
Update the
automated hypotheses automated robotic
Hypothesis is a set of mathematical equations expressed
system model generation and
experimentation
system as functions in W3C MathML-based format and is
associated with one or more simulation trial dataset,
consisting of tuples with input variables of equation and
Analysis of results Collection of experimental
New knowledge by statistics and observations and other its corresponding output as functionally dependent (FD)
machine learning meta-data
variables (the predictions). Phenomenon is represented
Fig. 6. Hypothesis driven closed-loop learning by at least one empirical dataset similar to simulation
trials. In the next step, the system deals with hypotheses
Adam follows a hypothetico-deductive methodology
and phenomena in the following way: 1) researcher has
(section 2). Adam abductively hypothesizes new facts
to provide some meta data about hypotheses and
about yeast functional biology, then it deduces the
phenomena; e.g., hypotheses need to be associated with
experimental consequences of these facts using its
the respective phenomena and assigned a prior
model of metabolism, which it then experimentally
confidence distribution (uniform by default according to
tests. To select experiments Adam takes into account
the principle of maximum entropy (3.2.3)); 2) functional
the variable cost of experiments, and the different
dependencies (FD) are extracted from equations in order
probabilities of hypotheses. Adam chooses its
to obtain database schema to store simulations and
experiments to minimize the expected cost of
experimental data; it should be mentioned that to
eliminating all but one hypothesis. This is in general a
precisely identify hypothesis formulation the special
NP complete problem and Adam uses heuristics to find
attributes for phenomena and hypothesis references are
a solution [65].
introduced into FD; 3) tuples are synthesized from
It is now likely that the majority of hypotheses in simulation trials and observational data by uncertain
biology are computer generated. Computers are pseudo-transitive closure and reasoning; 4) finally, the
increasingly automating the process of hypothesis probabilistic γ-DB database is formed. Once
formation, for example: machine learning programs phenomenon and hypothesis (with empirical datasets
(based on induction) are used in chemistry to help and simulation trials) are produced it becomes possible
design drugs; and in biology, genome annotation is to manipulate them with database tools.
essentially a vast process of (abductive) hypothesis
MayBMS provides tools to evaluate competing
formation. Such computer-generated hypotheses have
hypotheses for the explanation of a single phenomenon.
been necessarily expressed in a computationally
With prior probabilities already provided the system
amenable way, but it is still not common practice to
allows to make one or more (if new observational data
deposit them into a public database and make them
appears) Bayesian inference steps. In each step the prior
available for processing by other applications [65].
probability is updated to posterior according to Bayes’
The details describing the software and informatics theorem. As a result, hypotheses which better explain
decisions in the Robot Scientist project can be found in phenomenon get higher probabilities enabling
[65, 66] and online at the website http://www.aber.ac.uk/ researchers to make more confident decisions (see also
compsci/Research/bio/robotsci/data/informatics/). The 3.2.1). The γ-DB approach provides a promising way to
details for developing the formalization used for analyse hypotheses in large scale DIR as uncertain
Adam’s functional genomics investigations can be predictive database in face of empirical data.
found in [13, 39]. An ontology-based formalization
117
5 Examples of hypothesis-driven scientific mapping of all neural connections within
an organism's nervous system. The production and study
research of connectomes, known as connectomics, may range in
scale from a detailed map of the full set of neurons and
5.1 Besançon Galaxy model
synapses within part or all of the nervous system of an
Various models in astronomy heavily rely on organism to a macro scale description [15] of the
hypotheses. One of the most impressive is the Besançon functional and structural connectivity between all
galaxy model (BGM) [16, 60, 61] evolving for many cortical areas and subcortical structures. The ultimate
years and representing the population and structure goal of connectomics is to map the human brain. In
synthesis model for the Milky Way. It allows functional magnetic resonance imaging (fMRI),
astronomers to test hypotheses on the star formation associations are thought to represent functional
history, star evolution, and chemical and dynamical connectivity, in the sense that the two regions of the
evolution of the Galaxy. From the beginning, the aim of brain participate together in the achievement of some
the BGM was not only to be able to simulate reasonable higher-order function, often in the context of performing
star counts but further to test scenarios of Galactic some task. fMRI has emerged as a powerful tool used to
evolution from assumptions on the rate of star formation interrogate a multitude of functional circuits
(SFR), initial mass function (IMF), and stellar simultaneously. This has elicited the interest of
evolution. statisticians working in that area. At the level of basic
We will further focus on the renewed BGM [16], in measurements, neuroimaging data can be considered to
which authors draw their attention to the Galaxy thin consist typically of a set of signals (usually time series)
disk treatment and use of Tycho-2 as a testing dataset. at each of a collection of pixels (in two dimensions) or
The parameters of BGM (such as IMF, SFR and voxels (in three dimensions). Building from such data,
evolutionary track sets) explicitly and model ingredients various forms of higher-level data representations are
implicitly can be treated as hypotheses. Model employed in neuroimaging. In recent years a substantial
ingredients include the treatment of binarity, the local interest in network-based representations has emerged
stellar mass densities of thin disk, extinction model, in neuroimaging to use networks to summarize
age-metallicity and age-velocity relations, radial scale relational information in a set of measurements,
length, the age of the Galaxy thin disc, different sets of typically assumed to be reflective of either functional or
the star atmosphere models, etc. structural relationships between regions of interest in
the brain. With neuroimaging now a standard tool in
Tycho-2 dataset and χ2-type statistics test is used to clinical neuroscience, quickly moving towards a time in
test various versions of these hypotheses in order to which we will have available databases composed of
choose the most appropriate ones and update model to large collections of secondary data in the form of
better fit the provided data. The tests were made by network-based data objects is predictable.
comparing star counts and (B−V)T colour distributions
between data and simulations. Two different tests were One of the most basic tasks of interest in the analysis
used to evaluate the adequacy of the stellar densities of such data is the testing of hypotheses, in answer to
globally and to test the shape of the colour distribution. questions such as “Is there a difference between the
networks of these two groups of subjects?" Networks
Due to the fact, that some ingredients of the model are not Euclidean objects, and hence classical methods
are highly correlated (such as the IMF, SFR and the of statistics do not directly apply. Network-based
local mass density) the authors defined default models analogues of classical tools for statistical estimation and
as a combination of a new set of ingredients that hypothesis testing are investigated [21, 22]. Such
significantly improve the fit to Tycho data. So, 11 IMF research is motivated by the 1000 Functional
functions, 2 SFR functions, 2 evolutionary track sets, 3 Connectomes Project (FCP) launched in 2010 [7].The
sets of atmosphere models, 3 values for the age of the 1000 FCP [74] constitutes the largest data set of its kind
formation of the thin disk, 3 sets of values of the thin similarly to large data sets in genetics. Other projects
disk local stellar volume mass density were tested. As a (such as the Human Connectome Project (HCP)) are
result of testing, the two most appropriate IMS and SFR aimed to build a network map of the human brain in
hypotheses were chosen. Based on this experience, an healthy, living adults. The total volume of data
investigation of the thick disc is underway using SDSS produced by the HCP will likely be multiple
and 2MASS surveys. petabytes [46]. HCP informatics platform includes data
management system ConnectomeDB that is based on
5.2 Connectome analysis based on network data
the XNAT imaging informatics platform [47], a widely
In the neuroscience community the development of used open source system for managing and sharing
common paradigms for interrogating the myriad imaging and related data.
functional systems in the brain remains to be the core Visualization, processing and analysis of high-
challenge. Building on the term “connectome,” coined dimensional data such as images often requires some
to describe the comprehensive map of neural kind of preprocessing to reduce the dimensionality of
connections in the human brain, the “functional the data and find a mapping from the original
connectome” denotes the collective set of functional representation to a low-dimensional vector space. The
connections in the human brain (its “wiring diagram”) assumption is that the original data resides in a low-
[7]. More broadly, a connectome would include the
118
dimensional subspace or manifold [11], embedded in were significant to influence patterns of brain
the original space. This topic of research is called connectivity. The null hypothesis of no group
dimensionality reduction, non-linear dimensionality differences was rejected with high probability. Similarly
reduction, including methods for parameterization of for the three different age cohorts the null hypothesis of
data using low-dimensional manifolds as models. no cohort differences also was rejected with high
Within the neural information processing community probability.
this has become known as manifold learning. Methods On such examples it was shown [21] that the
for manifold learning are able to find non-linear proposed global test has sufficient power to reject the
manifold parameterizations of datapoints residing in null hypothesis in cases when mass-univariate approach
high-dimensional spaces, very much like Principal (considered to be the gold standard in fMRI research
Component Analysis (PCA) is able to learn or identify [43]) fails to detect the differences at the local level.
the most important linear subspace of a set of data According to the mass-univariate approach statistical
points (projecting data on a n-dimensional linear analysis is performed iteratively on all voxels to identify
subspace which maximizes the variance of the data in brain regions whose fMRI detected responses display
the new space). significant statistical effects. Thus it was shown that a
In [21] necessary mathematical properties associated framework for network-based statistical testing is more
with a certain notion of a ‘space’ of networks used to statistically powerful, than a mass-univariate approach.
interpret functional neuroimaging connectome-oriented It is expected that in the near future there will be a
data are established. Extension of the classical statistics plethora of databases of network-based objects in
tools to network-based datasets, however, appeared to neuroscience motivating the development and extension
be highly non-trivial. The main challenge in such an of various tools from classical statistics to global
extension is due to the fact that networks are not network data.
Euclidean objects (for which classical methods were
In the [70] paper discussion the relationship between
developed) – rather, they are combinatorial objects,
neuroimaging and Big Data areas it is analyzed how
defined through their sets of vertices and edges. In [21]
modern neuroimaging research represents a
it was shown that networks can be associated with
multifactorial and broad ranging data challenge,
certain natural subsets of Euclidean space, and
involving the growing size of the data being acquired;
demonstrated that through a combination of tools from
sociological and logistical sharing issues; infrastructural
geometry, probability on manifolds, and high-
challenges for multi-site, multi-datatype archiving; and
dimensional statistical analysis it is possible to develop
the means by which to explore and mine these data. As
a principled and practical framework in analogy to
neuroimaging advances further, e.g. aging, genetics, and
classical tools. In particular, an asymptotic framework
age-related disease, new vision is needed to manage and
for one- and two-sample hypothesis testing has been
process this information while marshalling of these
developed. Key to this approach is the correspondence
resources into novel results. It is predicted that on this
between an undirected graph and its Laplacian, where
way “big data” can become “big” brain science.
the latter is defined as a matrix (associating with a
network). Graph Laplacian appeared to be particularly 5.3 Climate in Australia
appropriate to be used for such matrices. The space of
graph Laplacians is used working in certain subsets of Another view on hypothesis representation and
Euclidian space which are some submanifolds of the evaluation is presented in [41]. Authors argue, that as
standard Euclidian space. long as in DIS data relevant to some hypotheses gets
The 1000 FCP describes functional neuroimaging continuously aggregated as time passes, hypotheses
data from 1093 subjects, located in 24 community-based should be represented as programs that are executed
centers. The mean age of the participants is 29 years, and repeatedly, as new relevant amounts of data gets
all subjects were 18 years-old or older. It is of interest to aggregated. Their method and techniques are illustrated
compare the subject-specific networks of males and by examining hypotheses about temperature trends in
females in the 1000 FCP data set. In [21] for the 1000 Australia during the 20th century. The hypothesis being
FCP database comparing of networks with respect to the tested comes from [42], stated that the temperature
sex of the subjects, over different age group, and over series is not stationary and is integrated of order 1 (I(1)).
various collection sites is considered. It is shown that it is Non-stationarity means that the level of the time series
necessary to compute the means in each subgroup of is not stable in time and can show increasing and
networks. This was done by constructing the Euclidean decreasing trends. I(1) means that by differentiating the
mean of the Laplacians for each group of subjects in stochastic process a stationary process (main statistical
different age groups. Such group-specific mean properties of the series remain unchanged) is obtained.
Laplacians can then be interpreted as the mean functional Phillips-Perron test and the Kwiatkowski–Phillips–
connectivity in each group. Such approach provides for Schmidt–Shin (KPSS) test are used and both of them
building the hypothesis tests about the average of are executed in R. Several data sources are crawled: 1)
networks or groups of networks to investigate the effect The National Oceanographic and Atmospheric
of sex differences on entire networks. Administration marine and weather information, 2)
Australian Bureau of Meteorology dataset. The
For the 1000 FCP data set it was tested using the framework consists of R interpreter and R SPARQL,
two-sample test for Laplacians whether sex differences tseries packages. Authors also used agINFRA for
119
computation and rich semantics to support traditional formulation applying logical reasoning, various methods
scientific workflows for natural sciences. Authors for hypothesis modeling and testing (including classical
received further evidence on different independent statistics, Bayesian hypothesis and parameter estimation
dataset that time series is integrated of order 1. methods, hypothetico-deductive approaches) are
briefly introduced. Special attention is given to
5.4 Financial market discussion of the data mining and machine learning
Efficient-market hypothesis (EMH) is one of the methods role in process of generation, selection and
most prominent in finance and “asserts that financial evaluation of hypotheses as well as the methods for
markets are "informationally efficient"”. In [8] authors motivation of new hypothesis formulation. Facilties of
test the weak form of EMH, stating that prices on traded informatics for support of hypothesis-driven
assets (e.g., stocks, bonds, or property) already reflect experiments, considered in the paper, are aimed at the
all past publicly available information. The null conceptualization of scientific experiments, hypothesis
hypothesis states that successive prices changes are formulation and browsing in various domains (including
independent (random walk). The alternative hypothesis biology, biomedical investigations, neuromedicine,
states that they are dependent. To check if the astronomy), automatic organization of hypothesis-
successive closing prices are dependent of each other driven experiments. Examples of scientific researches
the following statistical tests were used: a serial applying hypotheses considered in the paper include
correlation test, a runs test, an augmented Dickey-Fuller modeling of population and structure synthesis of the
test and the multiple variance ratio test. Tests were Galaxy, connectome-related hypothesis testing,
performed on daily closing prices from the six European studying of temperature trends in Australia, analysis of
stock markets (France, Germany and UK, Greece, stock markets applying the EMN (Efficient market
Portugal and Spain) during the period between 1993 and hypothesis), as well as algorithmic generation of
2007. The result of each test states whether successive hypotheses in the IBM Watson project applying the
closing prices are dependent of each other. NLP and knowledge representation and reasoning
technologies. An introduction into the state of the art of
Test provides evidence that for monthly prices and the hypothesis-driven research presented in the paper
returns the null hypothesis should not be rejected for all opens a way for investigation of the generalized
six markets. If daily prices are concerned the null approaches for efficient organization of hypothesis-
hypothesis is not rejected for France, Germany, UK and driven experiments applicable for various branches
Spain, but this hypothesis is rejected for Greece and of DIS.
Portugal. However, on the 2003-2007 dataset the null
hypothesis for these two countries is not rejected as
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