Modest Use of Ontology Design Patterns in a Repository
              of Biomedical Ontologies

             Jonathan M. Mortensen, Matthew Horridge, Mark A. Musen, and
                                    Natalya F. Noy

                      Stanford Center for Biomedical Informatics Research
                         Stanford University, Stanford CA 94305, USA



         Abstract. Ontology Design Patterns (ODPs) provide a means to capture best
         practice, to prevent modeling errors, and to encode formally common modeling
         situations for use during ontology development. Despite the popularity of ODPs
         and supposed positive effects from their use, there is scant empirical evidence
         of their level of adoption in real world ontologies or on their effectiveness.
         Knowing the goals of ODPs, they may assist in the development of large-scale
         biomedical ontologies. Before studying ODP effectiveness and applicability, we
         ask the following questions to understand better the landscape of ODP use: Are
         ODPs used in biomedical ontologies? Which patterns do the ontology developers
         use? In which ontologies? How frequently are patterns used? To answer these
         questions, we determined the adoption of ODPs from two popular ODP libraries
         among the ontologies in BioPortal, a large ontology repository that contains over
         300 biomedical ontologies. We encoded 68 ODPs from two online libraries in the
         Ontology Pre-Processor Language, and, using these encodings, determined ODP
         prevalence in BioPortal ontologies. We found modest use of ODPs, with 33%
         of the ontologies containing at least one pattern. Upper Level Ontology,
         Closure, and Value Partition were the three most commonly used
         patterns, occurring in 20%, 9%, and 6% of the BioPortal ontologies, respectively.
         The low prevalence of ODPs may be due to lack of proper tooling, lack of
         user knowledge of and education about them, the age of the ontologies in the
         repository, or the specificity of some ODPs. We noted that there is a tension
         between the high expressivity of many ODPs and the goal of maintaining low
         expressivity of some biomedical ontologies. Additional tooling is necessary to
         make ODPs more accessible to domain experts. Furthermore, we suggest that
         ODPs may be developed in a bottom-up fashion, much like software-design
         patterns. 1

         Keywords: OWL, biomedical ontologies, BioPortal, Ontology Design Pattern,
         Ontology Pre-Processor Language


1      Ontology Design Patterns
There is a large body of research establishing and creating Ontology Design Patterns
(ODPs) [11, 5]. Yet, there is little work to determine their use or effectiveness.
In biomedicine, the development and use of ontologies are growing rapidly. This
 1
     Accompanying online resources at http://www.stanford.edu/people/mortensen/odp
2

development process can be difficult and/or error prone. As such, ODPs would likely
assist with this development process. In this study, as initial work in evaluating the
effectiveness and applicability of ODPs in biomedical ontologies, we examine the
prevalence of ODPs in a large corpus of ontologies related to biomedicine.
1.1   ODPs and ODP libraries
Software Design Patterns emerged in the 1990s, capturing recurring software design
techniques seen in software [10]. Following a similar motivation, the Semantic Web
community developed ODPs to alleviate some of the complexities in developing
ontologies. ODPs, defined as “a modeling solution to solve a recurrent ontology design
problems” [11], capture best practice and common modeling situations. The developers
of ODPs suggest that by using the patterns, one can more easily avoid modeling errors,
improve ontology quality, maintainability, and reuse [3].
    ODPs have become quite popular recently, with multiple workshops held at ISWC,
including one during ISWC 2012. There are two online catalogs of ODPs, the
Manchester ODPs Public Catalog for bio-ontologies (MBOP) and OntologyDesignPat-
terns.org (ODP-Wiki) [9, 1]. These catalogs describe each pattern by the problem that it
solves, the proposed solution, and the formal representation by which to instantiate the
pattern. MBOP contains 17 patterns derived from its authors’ experience in modeling
ontologies in the biomedical domain and working with OWL-based ontologies in
general. ODP-Wiki is a crowd-sourced effort to create an ODP library. The website
owners ask for pattern submissions and then a committee reviews these submissions for
approval. The approved patterns are then noted as such online. As of this writing, the
committee has not approved any patterns but there are over 150 submissions.
    Most of the submissions on ODP-Wiki are “content” ODPs. However, the site cate-
gorizes many other different types of ODPs. ODP-Wiki includes “structural” (methods
to workaround for language expressivity limitations or define ontology shape/structure),
“content” (modeling solutions for a specific domain), “correspondence” (methods to re-
engineer an ontology to a different form or map an ontology to another), “reasoning”
(patterns that enable one to obtain desired reasoning results),“presentation” (good prac-
tices for readability and usability), and “lexico-syntactic” (mapping linguistic structures
to ontology entities) patterns—a categorization based on descriptions by Gamgemi and
colleagues [11]. MBOP categorizes patterns as “extension” (workarounds for language
expressivity limitations), “good practice” (good modeling practice) and “domain
modeling” (solutions specific to certain domains). The “structural” classification
encompasses the majority of the MBOP patterns. In this work, the structural and
content ODPs are most relevant. Structural patterns are either logical, adding logical
expressions not contained directly in the ontology language, or architectural, defining
the structure/hierarchy of the ontology itself. Content ODPs model a specific domain
situation, and are directly re-usable (i.e., they should be directly imported into an ontol-
ogy and used). We omit lexico-syntactic, presentation, reasoning, and correspondence
patterns from this work, as we cannot test for them using our framework.
    Accompanying the MBOP, the Manchester group also developed the Ontology Pre-
Processing Language (OPPL), both a language based on the Manchester syntax for
OWL, and a software library, which leverages the OWL-API [14]. OPPL provides a
way to manipulate ontologies, query for ODPs and instantiate them [16, 15, 2].
                                                                                          3

1.2     Biomedical Ontologies
In biomedicine, ontology use is rapidly increasing [7, 21]. For example, the National
Center for Biomedical Ontology’s BioPortal,2 a repository of biomedical ontologies,
contains over 300 ontologies and controlled terminologies as of this writing [18].
Biologists use biomedical ontologies to manage the large amount of data. Hospitals and
related entities use them in the process of recording information about clinical encoun-
ters, during clinical decision support, billing, and so on. Because biomedical ontologies
are often large and complex, developing them and ensuring that they conform to best
practices poses a formidable challenge. Even the widely used ontologies frequently
contain modeling errors. For instance, Rector and colleagues discovered modeling
issues in SNOMED CT, one of the most widely used biomedical ontologies [19].
Researchers have found modeling errors in the National Cancer Institute thesaurus [8].
ODPs may be especially important in assisting with the challenge of modeling the large
and complex biomedical domains while preventing errors. Before assessing the effect of
using ODPs on the biomedical ontology modeling process, we first find the prevalence
of ODPs in a large biomedical ontology corpus.
2      Methods
We quantified the use of ODPs from both MBOP and ODP-Wiki in BioPortal using
OPPL and the OWL API. We first encoded ODPs in OPPL and validated their
correctness (1) by using an expert opinion and (2) by comparing them to the examples
in the library that served as a gold standard. We then obtained the ontologies from
BioPortal, removing cases by use of predefined filtering criteria (See section 2.2). We
normalized the ontologies to remove any differences in how they were specified, and
then checked both the normalized and the original version for each encoded pattern,
first filtering out patterns that cannot be represented in the ontology because it lacks the
proper relations.
2.1     Pattern Selection
We used the following criteria to select the set of patterns for this study: The pattern
must be (1) detectable, (2) non-trivial (that is, not just a template), (3) positively
reviewed (if a review is available), and (4) available in a public catalog (in our case,
either MBOP or ODP-Wiki). We use these criteria for the following reasons:
 1. Using only detectable patterns may seem obvious; however, there are many patterns
    such as n-ary relations, or re-engineering patterns that cannot be detected
    without more information than just the ontology.
 2. A template style pattern may not require the presence of any particular elements.
    Thus, it would be trivially present even if the ontology contained no elements of
    the pattern.
 3. When available, we considered review information on ODP-Wiki. Poorly reviewed
    patterns may not yet be refined, making them difficult to encode, especially if they
    have a logical error.
 4. We chose only publicly available patterns, as it is a necessary condition for both
    reproducibility of this study and the expectation of pattern re-use.
 2
     http://bioportal.bioontology.org
4

Applying the criteria above to MBOP and ODP-Wiki, produced the following results:

    – From the 17 patterns in MBOP, we used 15. The remaining 2 were undetectable
    – From the 150 patterns in ODP-Wiki, we used 53. The remaining patterns were
      either optional or not positively reviewed.

      Thus, we selected 68 patterns of 167.
2.2    Ontology Selection
From the available ontologies in BioPortal, we selected those ontologies that were
publicly available, parseable, locatable (a file was easily obtainable), non-retired,
available as a single file, and available as either OWL or OBO format. Applying these
criteria to the 312 ontologies that were available in BioPortal as of January 2012,
resulted in a set of 256 ontologies.
2.3    Pattern Encoding
OPPL and the OWL API are open-source standard libraries available to work with
ontology design patterns and ontologies. We encoded the MBOP and ODP-Wiki
patterns with OPPL. Some patterns could not be encoded in OPPL. Those patterns
we encoded directly in Java using the OWL API. An example OPPL encoding of the
Value Partition pattern (a way to specify a set of disjoint qualities the describe a
concept) follows:

      ?v1:CLASS, ?v2:CLASS, ?param:CLASS
      SELECT
      ASSERTED ?param EquivalentTo ?v1 or ?v2,
      ASSERTED ?v1 DisjointWith ?v2
      BEGIN
      ADD ?v1 subClassOf Thing
      END;

     In order to reduce computational complexity, we pruned pattern–ontology pairs by
first checking whether the ontology contains the specific relationships between concepts
that a given ODP requires. An ontology without those relationships cannot have the
pattern as the catalog specifies it. Furthermore, for those patterns that could not occur
in any ontology from our selection, based on the required relationships, we did not
encode the pattern. In particular, many content patterns refer to specific relationships in
the ontology. For example, according to ODP-Wiki, the pattern Part Of requires the
relationship “isPartOf”. Thus, if an ontology does not have this relationship “isPartOf”,
we know that it will not have the pattern. When searching, we disregard the namespace
of any given pattern, in case the pattern simply uses a different namespace (i.e., we
only match on the URI fragment, not including the namespace). One might consider
searching with possible lexical variants of this relationship term to ensure one finds
occurrences which capture the intension of the specified relationship. However, the
point at which a given string no longer matches the initial string is not well defined.
Furthermore, content ODPs directly import a small module, thus the relation should not
vary across ontologies.
                                                                                            5

           Table 1. Transforms applied exhaustively to an ontology to normalize it.

                     Axiom                                      Transformation
prop min 1 C                                    prop some C
prop exactly n C                                prop min n C, prop max n C
prop value i                                    prop some i
Property in Anonymous Class                     Simplify Property (Removing inverses) and re-
                                                insert
C1 and (C2 and C3)                              C1 and C2 and C3
C1 or (C2 or C3)                                C1 or C2 or C3
C1 EquivalentTo C2                              C1 SubClassOf C2, C2 SubClassOf C1
C1 DisjointUnionOf C2 ... Cn                    DisjointClasses: C2 ... Cn, C1 EquivalentTo (C2
                                                ... Cn)
C1 or ... or Cn SubClassOf D1 and ... and Dn    C1 SubClassOf D1 ... Cn SubClassOf D1 ... C1
                                                SubClassOf Dn ... Cn SubClassOf Dn
DisjointClasses: C1 ... Cn                      Ci DisjointWith Cj for 1 <= i <j <=n



    Finally, during encoding, to gather additional information about a pattern, we noted
the OWL 2 description logic constructs each utilizes. We note these because certain
constructs have higher expressivity requirements. Higher expressivity comes at a higher
computational cost. This fact may provide insight as to why biomedical ontologies
instantiate only certain patterns.
2.4   Normalization
When specifying an ontology, one can represent the same conceptualization using
different language constructs. This phenomenon is particularly common in OWL. To
prevent missing a pattern that may be specified in a slightly different language than
that found in an ontology, we applied pattern detection to a normalized version of each
ontology as well. Table 1 lists the normalizations that we performed. These transfor-
mations follow from the OWL 2 specification and convert ‘syntactic sugar’ conventions
provided by the language to a standard form. For example, applying the transformations
to Dog EquivalentTo Canine results in Dog SubClassOf Canine and
Canine SubClassOf Dog. While one could use a reasoner to infer equality of
certain constructs, this was not computationally feasible in this study.
2.5   Computation
After creating a list of encoded patterns, and of original and normalized versions of
all ontologies in the study, we searched for each pattern in the ontologies using the
encodings and the software libraries. Checking for 68 patterns in nearly 300 ontologies,
some of which have tens of thousands of classes, is a computationally intensive
task. A brute-force approach to this task was unreasonable, as a single run through
all possible ontology–pattern pairs would have taken over a week. We performed
a few optimizations to speed up the runtime of the experiment. First, as described
before in section 2.3, we pruned the patterns first by searching whether or not the
ontology contains the necessary relations. Next, we created a specialized cache to
store computationally intensive search operations that are shared across multiple pattern
6

queries per ontology. Finally, we distributed the pattern search process to a large cluster
of 20 nodes, each with 24 cores and 96GB of RAM. We do not attempt to count
the number of times a pattern occurs in a given ontology, as doing so also increases
complexity. We limit the running time of any ontology–pattern pair to one week. During
our analysis, approximately 150 pairs did not complete. These were complex patterns
and complex ontologies (e.g., FMA and Normalization).


2.6   Validation

A pattern that is encoded (incorrectly) in a way that is too general could lead to a false
positive, matching any ontology. For example, encoding Value Partition without
the EquivalentClass component would match any ontology that has disjoint classes,
which is not a true instantiation of Value Partition. An incorrectly specified
pattern would lead to a false negative, not matching any ontology even though the
pattern is present. We therefore verified that the patterns were correctly encoded both by
involving an expert and by comparing them against a reference standard. The pattern
encodings were manually inspected by an author of this paper (MH). Second, where
possible, we tested the patterns and software against reference examples provided by
the catalogs. We expected to find each encoded pattern in its reference example. MBOP
provided example OWL ontology implementations of every pattern. Because ODP-
Wiki required the import of a specific ontology, the verification was trivial.


3     Results

Of the 68 patterns in the study, we encoded 8 patterns in OPPL, 5 with the OWL API,
manually verified 7, and pruned 47 content ODPs that contained relationships that
were not present in any of the ontologies in the study. These relationships included,
for example, “isRegionFor”, “hasRTMSCode”, “participatingInEvent”. One of the
patterns MBOP specifies is the Upper Level Ontology pattern. MBOP describes
the pattern as good practice that allows one to integrate different ontologies in a
grounded framework. To find the Upper Level Ontology pattern, we checked
whether each ontology imported a unique upper-level concept from either of the
following upper ontologies: DOLCE [12], BFO [13] or SUMO [17]. We manually
verified the remaining 7 patterns that matched the necessary relations for a pattern.
These patterns need not necessarily import the pattern, but only capture its intension
(e.g., GALEN). For brevity, Table 2 presents only a list of the positive patterns
and what ontologies instantiated them. We found that 14 patterns were present in
at least one ontology. 33% of the OWL and OBO format ontologies in BioPortal
contain a pattern, with Upper Level Ontology (20%), Closure (9%), and
Value Partition (6%) most common. Other commonly used patterns include
Normalization and Composite Property Chaining. Thirty ontologies in-
cluded more than one pattern. The Ontology of Biomedical Investigations included the
most patterns: DefinedClassDescription, Closure, Value Partition,
Sequence and Upper Level Ontology.
                                                                                               7

                   Table 2: Patterns and the ontologies that instantiate them.


                        Composite Property Chaining (7 Ontologies)
Model a double chain of properties, i.e. two chains that link four individuals.
Brucellosis Ontology                              SemanticScience Integrated Ontology
Infectious Disease Ontology                       Skin Physiology Ontology
Influenza Ontology                                SNOMED CT
RNA ontology

                                        Adapted SEP (1)
Properly propagate partomony
BioTop

                                       Closure (23)
Simulate the Closed World Assumption in a concrete class
Amino Acid                          Kinetic Simulation Algorithm Ontology
BioAssay Ontology                   Lipid Ontology
BioTop                              NanoParticle Ontology
Bleeding History Phenotype          Neomark Oral Cancer-Centred Ontology
Bone Dysplasia Ontology             Ontology for Biomedical Investigations
Breast Cancer Grading Ontology      Ontology for disease genetic investigation
Cancer Research and Management ACGT Ontology for Genetic Interval
Master Ontology
Cognitive Atlas                     Skin Physiology Ontology
DIKB-Evidence-Ontology              Subcellular Anatomy Ontology (SAO)
Gene Regulation Ontology            Suggested Ontology for Pharmacogenomics
IMGT-ONTOLOGY                       Vaccine Ontology
Infectious Disease Ontology

                                Defined Class Description (6)
Create If-Then structures in OWL DL
Adverse Event Reporting ontology    Ontology for Biomedical Investigations
Cancer Research and Management ACGT Ontology for Drug Discovery Investigations
Master Ontology
NanoParticle Ontology               SysMO-JERM

                                     Value Partition (16)
Model values of non-overlapping attributes exhaustively
Adverse Event Reporting ontology                  Influenza Ontology
Basic Formal Ontology                             OBOE
Basic Vertebrate Anatomy                          Ontology for Biomedical Investigations
BioTop                                            Ontology for disease genetic investigation
CAO                                               Ontology for Genetic Interval
Computer-based Patient Record Ontology            RNA ontology
General Formal Ontology                           Situation-Based Access Control
Infectious Disease Ontology                       Vaccine Ontology

                                       Normalization (14)
8

Ensure maintainability and explicit semantics by allowing polyhierarchy only through inference
Basic Formal Ontology                             PMA 2010
Human developmental anatomy, abstract ver-        Proteomics Pipeline Infrastructure for CPTAC
sion
IMGT-ONTOLOGY                                     SemanticScience Integrated Ontology
Mouse gross anatomy and development               Traditional Medicine Constitution Value Set
NIFSTD                                            Traditional Medicine Meridian Value Sets
OBO relationship types                            Traditional Medicine Other Factors Value Set
Pilot Ontology                                    Traditional Medicine Signs and Symptoms
                                                  Value Set

                                   Upper Level Ontology (53)
Create ontologies with a consistent, philosophically grounded upper ontology
Adverse Event Reporting ontology                  Mental Functioning Ontology
Basic Formal Ontology                             Mosquito insecticide resistance
Basic Vertebrate Anatomy                          NanoParticle Ontology
BioModels Ontology                                Neomark Oral Cancer Ontology
BIRNLex                                           Neural ElectroMagnetic Ontologies
Bone Dysplasia Ontology                           NIF Cell
Brucellosis Ontology                              NIF Dysfunction
Cancer Chemoprevention Ontology                   NIFSTD
Cancer Research and Management ACGT               NMR-instrument specific component of
Master Ontology                                   metabolomics investigations
CAO                                               Ontology for Biomedical Investigations
Cardiac Electrophysiology Ontology                Ontology for disease genetic investigation
Chemical Information Ontology                     Ontology for Drug Discovery Investigations
Cognitive Paradigm Ontology                       Ontology for General Medical Science
Computer-based Patient Record Ontology            Ontology for Genetic Interval
Drosophila development                            Ontology for Parasite LifeCycle
eagle-i research resource ontology                Ontology of Data Mining
Electrocardiography Ontology                      Ontology of Glucose Metabolism Disorder
FGED View                                         Ontology of Medically Related Social Entities
Gene Regulation Ontology                          Phenotypic quality
General Formal Ontology                           RadLex
General Formal Ontology: Biology                  RNA ontology
Host Pathogen Interactions Ontology               Skin Physiology Ontology
IEDB View                                         Sleep Domain Ontology
Infectious Disease Ontology                       Subcellular Anatomy Ontology (SAO)
Influenza Ontology                                Translational Medicine Ontology
Information Artifact Ontology                     Vaccine Ontology
Interaction Network Ontology

                                           Agent Role (1)
Represent agents and the roles they play
ICPS Network

                                      Classification (1)
Represent the relations between concepts and entities to which concepts can be assigned
                                                                                                 9

ICPS Network

                                         Componency (1)
Represent (non-transitively) that objects either are proper parts of other objects, or have proper
parts
Computational Neuroscience Ontology

                                         Object Role (2)
Represents objects and the roles they play
ICPS Network                                       International Classification for Nursing Practice

                                            Part Of (2)
Represent entities and their parts.
Ontology for Genetic Interval                      SysMO-JERM

                                             Place (2)
Talk about places of things
Galen                                              International Classification for Nursing Practice

                                        Sequence (4)
Model a sequence of events occuring one after another
FGED View                                          Ontology for Biomedical Investigations
IEDB View                                          Vaccine Ontology




   We also recorded the more complex logical constructs of the patterns in MBOP
(Table 3). A pattern that utilizes one of these constructs cannot belong to the OWL 2
EL Profile, a less expressive, more computationally efficient fragment of OWL 2.



4   Discussion
Our results show a very modest use of patterns in biomedical ontologies in BioPortal.
Of the 68 patterns that we studied (which we filtered from the initial list of 167), only 14
appeared among the almost 300 ontologies. Ontology developers may utilize patterns
because of documentation, popularity, and support in development tools. For example,
all ontologies using Upper Level Ontology, the most common pattern, instanti-
ated the BFO, likely due to the OBO Foundry’s popularity in the biomedical community
and its emphasis on using an upper level ontology. The Protégé ontology development
environment provides a quick method to instantiate Closure, Value Partition
(DisjointUnionOf), and Composite Property Chaining. We believe that the
easy accessibility of these patterns from this tool accounts for their use. While
Composite Property Chaining is not explicit in Protégé, after creating prop-
erty chains, composing them is trivial. Normalization is both a simple idea to
follow (perhaps difficult in practice), and well explained by Rector et al. [20]. Finally,
10

                    Table 3. OWL 2 logical constructs in MBOP patterns.

                                  All    Functional   Cardinality Re- Disjunction
                                  Values Property     striction       (Union)
                                  From
Entity Feature Value                           4            4               4
Selector                                                                    4
Normalization
Upper Level Ontology
Closure                             4
Entity Quality                      4                       4               4
Value Partition                                                             4
Entity Property Quality                        4                            4
Defined Class Description
Interaction Role Interaction        4                       4               4
Sequence                                       4
Composite Property Chaining
List                                           4
Adapted Structure, Entity, Part                                             4
Nary Datatype
Exception                                                   4               4
Nary Relationship




with only a few additions to the Relations Ontology (RO), an ontology that can be used
along with BFO, the Sequence pattern from MBOP can be used.
    We found only a subset of patterns in a subset of the BioPortal ontologies. Despite
the suggested positive effects of ODPs, the relatively modest use of ODPs in BioPortal
may be due to ontology age, domain specificity, minimal tooling support, lack of pattern
portability and generality, and a tension between the high logical expressivity of certain
patterns and a concurrent desire for minimally expressive biomedical ontologies to
enable computationally tractable reasoning (because of their large size). With regard
to ontology age, it is clear that older ontologies that began development before the
introduction of ODPs may not have them, as restructuring an ontology to incorporate
an ODP during maintenance may be impractical. Also, one might suggest that many
patterns are not found simply because they are not related to the biomedical domain.
    Of more relevance is the apparent lack of end-user tooling for instantiating ODPs.
The XD Tools provide with such functionality as a plugin [6]. OPPL is also available as
a Protégé plugin. However, a domain expert may not be familiar with ODPs, may not
necessarily know how to use ODPs or OPPL, and may not even seek out the plugins.
Concurrently, Protégé and other widely used ontology development tools do not have
a general method to instantiate ODPs. However, for those patterns that are already
available in a development environment (Closure, Value Partition), we do see
their occurrence. In this study, we cannot easily link pattern usage and any particular
ontology development environment. However, most biomedical ontology developers do
use Protégé. Thus, we suggest that for ODP use to increase, end-user oriented ontology
                                                                                      11

development environments must include a way to instantiate various patterns, including
those available in the ODP public libraries. Furthermore, such tools could note the use
of patterns in the source file of the ontology.
    We have noted the opposing tension in the expressivity in the patterns and
biomedical ontologies. The OWL 2 EL profile in many ways was designed with large
scale ontologies in mind. SNOMED CT [22, 4] served as its driving example. Table 3,
which lists the constructs that each pattern uses, shows that only 25% of the MBOP
patterns follow the OWL 2 EL profile. There is a dilemma: Patterns are designed to
assist in reducing errors in large ontologies, but by using them, reasoning (and finding
errors) becomes computationally intractable. This dilemma may explain the lack of
ODP use by some ontologies, as they maintain something similar to EL expressivity.
    Additionally, we found that BioPortal ontologies used more patterns from MBOP
than from ODP-Wiki. MBOP has patterns oriented toward biomedical applications,
explaining a portion of this bias. However, we found very few patterns from ODP-
Wiki. Many patterns in ODP-Wiki either were domain specific, or, by definition, their
instantiation required inclusion of a small ontology unit. While many ontologies might
follow the intension of the content ODPs on ODP-Wiki, they did not import the
required ontology to truly instantiate the pattern. Thus, more generalizable patterns,
and a method to capture the intension of a content ODP might also increase ODP use.
4.1   Future Work
We consider the formalization of software-design patterns in a bottom–up fashion.
Gamma and colleagues extracted recurring patterns from existing software, suggesting
these patterns constituted best practice in solving various software development
problems [10]. Contrary to this method, the development of ODPs in the Semantic Web
community appears to be top–down, especially in the case of content ODPs. Instead,
we propose to find ODPs in a bottom-up fashion, as with software design patterns, by
finding recurring patterns in large corpora of ontologies, such as BioPortal.

5     Conclusions
Ontology Design Patterns provide a means to enhance ontology development by cap-
turing best practice and reducing errors. As such, ODPs may be especially applicable
to large-scale biomedical ontology development. As a starting point for a larger project,
we first find the prevalence of ODPs in biomedical ontologies. To do so, using the
available software for manipulating ODPs, we surveyed their use in BioPortal,a large
repository of biomedical ontologies. We found only a small subset of patterns in use
in a portion of the corpus, with Upper Level Ontology being the most common
pattern. To increase future ODP use in biomedical ontologies, we highlight a need for
end-user ontology development tools that include a way to instantiate ODPs and a need
for consideration of the logical expressiveness of ODPs . Finally, we suggest a bottom-
up approach to develop generalized ODPs for re-use.

Acknowledgments
This work was supported by the NIH Grants GM086587, HG004028, and LM007033.
We thank Luigi Iannone for assistance with OPPL.
12

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