=Paper= {{Paper |id=None |storemode=property |title=Making context explicit towards decision support for a flexible scientific workflow system |pdfUrl=https://ceur-ws.org/Vol-696/paper1.pdf |volume=Vol-696 }} ==Making context explicit towards decision support for a flexible scientific workflow system== https://ceur-ws.org/Vol-696/paper1.pdf
                     CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




                         Making context explicit towards decision support
                            for a flexible scientific workflow system
    Xiaoliang Fan (1, 2, xiaoliang.fan@gmail.com), Patrick Brézillon (1, patrick.brezillon@lip6.fr),
               Ruisheng Zhang (2, zhangrs@lzu.edu.cn) and Lian Li (2, lil@lzu.edu.cn)

                                     (1) LIP6, Box 169, Université Pierre et Marie Curie
                                             4 Place Jussieu, Paris 75005 France

                          (2) School of Information Science and Engineering, Lanzhou University
                                  222 South Tianshui Road, Lanzhou 730000 P.R.China



                          Abstract                                   methods, change parameters, re-design the experiment) is
                                                                     measured by a decision node in workflow design
  Scientific workflow (SWF) system is a specific workflow            accompanying with a numerical value (e.g. IF the variable
  management system applied to science arena. For years,             is greater than 5, THEN execute the activity A, ELSE
  SWF systems are widely applied to many applications,               execute activity B; WAIT for 2 minutes to execute activity
  namely in physics, climate modeling, drug discovery                C). However, scientific discovery is by nature a
  process, etc. However, current SWF systems face the                knowledge-intensive one (van der Aalst et al., 2005) that
  challenge to adapt the flexibility and lack of decision            scientists' decisions rely not only on data and information
  support for scientist. We believe the major reason for the
                                                                     available, but also on a learning process in which user’s
  failure is due to do not make context explicit. We propose a
  solution to introduce contextual graphs (CxG) in the four
                                                                     preference, knowledge, and situation are captured to adapt
  phases of the SWF lifecycle, each of which is expressed in         the human-centered processes.
  a standard format, including a case study in virtual                 Such challenges mentioned above become an obstacle
  screening. Contextual graph allows to model scientists’            when scientists are making adaptive decisions to deliver
  decision making processes as a uniform representation of           new outcomes with fresh data and its context (Fan et al.,
  knowledge, reasoning, and of contexts, so that scientists          2010). Brézillon and Pomerol (1999) define context as
  are closely involved in each phase of SWF lifecycle to             “what constrains the resolution of a problem without
  maximize the decision support. Finally, we conclude and            explicit intervention in it”. We believe that the main
  highlight that using CxG is the key human-centered                 reason for this failure is largely due to the lack of context
  process for SWF systems.                                           management in an explicit way. In this paper we propose
                                                                     four ways of making context explicit in scientific
                      Introduction                                   workflow, by introducing contextual graph to in the four
Scientific workflow system liberates the computational               phases of scientific workflow lifecycle. Representing and
scientists from burden of data-centric operations to                 making “context” explicit in SWF system would provide
concentration on their scientific problems (Altintas et al.,         sustainable decision supports for scientists by formalizing
2004; Goble et al., 2007). However, it is not yet satisfied,         their research, strategies, and customization information,
considering that computational science (Roache, 1998) is             where elements of knowledge, reasoning and contexts are
always reproduced in a flexible and exploratory pattern.             represented in a uniform way.
Consider virtual screening (Chen & Shoichet, 2009) for                 Hereafter, the paper is organized in the following way.
example, the choice of one software over others depends              Section 2 introduces the four phases of the scientific
much on contextual information that are highly specific of           workflow lifecycle. Section 3 investigates the possibility
the situation at hand, and where, when, how and by whom              of integrating contextual graphs to the four phases of
the scientific workflow is executed. Thus a strong and               scientific workflow lifecycle through a case study in
sustainable decision support is urged for scientists to              virtual screening. Section 4 discusses previous works on
transfer hypotheses to discovery.                                    workflow flexibility in order to point out what is reusable
  Workflow flexibility becomes a critical challenge to deal          while problems remain to support decision-makings in a
with intermittently available resources, execution failures,         flexible scientific workflow system. The general
and to support human-centric decision-makings. However,              conclusion and future work in Section 5 closes the paper.
identifying how scientists make decisions to address
workflow flexibility is a very complicated issue. The ways                     Scientific Workflow Lifecycle
of scientists make their decision vary from one another: (1)         Scientific workflow lifecycle is coming from workflow
based on their past experience considering successful or             lifecycle (van de Aalst & van Dongen, 2003; Gil et al.,
failed ones; (2) inherited from the best practices within            2007; Deelman & Chervenak, 2008). It normally starts
science communities; (3) from the observed intermediate              from the scientific hypotheses (Beaulah et al., 2008;
results; and (4) just follow their own distinguished way.            Tadmor & Tidor, 2005; Claus & Johnson, 2008) to reach
Various approaches (Zhang et al., 2008; Courtney, 2001;              a specific experimental goal, which includes four phases
Tabak et al., 1985) are proposed to get user involved to             (see Figure 1):
describe their decision making processes. Normally in
such applications, a decision making (e.g., choose


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              CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




                                                                       iterative manner. Furthermore, it must then be
                                                                       facilitated to publish the workflow on a
                                                                       repository, so that SWF could be archived for
                                                                       re-use later.
                                                                  Figure 1 shows the relationship among each phases
                                                             of scientific workflow lifecycle: hypotheses arrive as
                                                             keywords to search pre-existing scientific workflow in
                                                             SWF repository; then scientist begin to design the
                                                             workflow model and maintain the mapping from an
                                                             abstract workflow to a concrete one; workflow execution
                                                             phase enacts the workflow model on available resources
                                                             according to data and control dependencies; if a change is
                                                             encountered, there is an iterative process to re-design the
                                                             workflow model as well as re-execute the workflow
                                                             instance; if executed successful, scientist will publish the
                                                             workflow in the SWF repository for the sake of
           Figure 1: SWF lifecycle
                                                             reproduction in the research communities.
                                                                 Current studies (van de Aalst & van Dongen, 2003;
   Workflow Searching: before initiating a brand
                                                             Deelman & Chervenak, 2008) on SWF lifecycle
    new workflow designing, scientists get used to
                                                             generally result in the weakness to manage the workflow
    firstly consult a public SWF repository for
                                                             changes and exceptions. We believe that the major failure
    searching previously published workflows
                                                             is due to do not make context explicit in the SWF systems.
    (Wroe et al., 2007). Once found, it would be
    easy to reproduce the pre-existing workflow to
    constitute a new one. Workflow searching                    Make Context Explicit in SWF Lifecycle
    results of sharing SWF considered with its               Representing and making context explicit in SWF system
    context of use. The more shared SWFs are taken           is a challenge that could promote a SWF system more
    place in the SWF repository, the more accurate           flexible and enhance its intelligence to facilitate effective
    the searching result would be.                           decision-makings. In this section, we discuss managing
   Workflow Designing is then initiated for                 contexts explicit throughout the four phases of the SWF
    constructing a workflow model (Ludascher et al.,         lifecycle, each of which is described using a standard
    2009). An abstract workflow model will firstly           format including: motivation, realization approach,
    be designed, in which scientific tasks and their         example, and discussion.
    execution orders, as well as data and its                  The example is represented in the Contextual graphs
    dependencies will be described. Secondly, the            formalism (Brézillon, 2005) through a case study entitled
    phase involves the mapping from abstract                 “Virtual screening research on avian influenza H5N1
    workflow to concrete/executable workflow                 virus”, which aims to find dozens of drug candidates for
    where the required resources are selected. By            H5N1 virus (He et al., 2008), by docking 7.7 million
    mapping the workflow instance onto the                   small molecules separately on H5N1 protein (Chen &
    available execution resources, an executable             Shoichet, 2009). Figure 2 shows a docking example,
    workflow is created for the next phase.                  which binds a molecule (ZINC12050767) to a virus
   Workflow Execution is the enactment of                   protein (H5N1 PAC Polymerase, known as Bird flu)
    executable workflow by a workflow engine                 through the Dock 6.2 software. Virtual screening could be
    (Deelman & Chervenak, 2008), in which input              considered as millions of docking procedures on the PAC
    data is consumed and output data is produced             protein.
    (Tan et al., 2010). Workflow engine follows the
    order of tasks and their dependencies defined in
    the workflow model. It is common to re-execute
    the workflow iteratively, considering the
    evolutionary changes of workflow model (e.g.,
    in workflow design, adding or skipping tasks,
    and altering task dependencies) or momentary
    changes of a running workflow instance (e.g.,
    making local decisions in response to a special
    situation, alter decision after analysing observed
    intermediate result, reporting exceptional cases).                       Figure 2: Docking example
   Workflow Publishing is a post-execution phase
    for scientists to interpret workflow results (Tan           The application is not only a time-consuming workflow
    et al., 2010; Ludascher et al., 2009) and to             application in which intensive computing is expected to
    publish the SWF in its context of use (Wroe et           be performed by docking software, but also a very flexible
    al., 2007; Deelman & Gil, 2006). Depending on            one that there is no unique solution for each computing
    the workflow outcomes and analysis results, the          because they vary from each other on selecting docking
    original hypotheses or experimental goals may            software. For example, scientists should identify the
    be revised or refined, giving rise to another            context in which the experiment is organized as a
    round of workflow design/execution in an                 scientific workflow. According to the current focus and


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                     CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




context, they link a specific resource (e.g., software,            Example: In Figure 4 (Left), CE1 is a contextual element
database, and instrument) with the workflow to realize a           (blue circle with number 1). The instantiation of the CE1
specific task. The concept of human-centered process is            (Is the protein rigid or flexible?) leads to the generation
particularly relevant in such domains.                             of two scientific workflow instances in Figure 4 (Right):
  Figure 3 provides the definition of the elements in a            one is SWF_1 (i.e. value of CE2= “Rigid”), and the other
contextual graph (actions, contextual elements, sub-graphs,        is SWF_2 (i.e. value of CE2=“Flexible”). In the
activities and temporal branching). A more complete                application, if scientists want to do a rigid virtual
presentation of this formalism and its implementation can          screening, “rigid” will become a keyword when
be found in (Brézillon, 2005).                                     performing the searching. Thus, SWF_1 will be selected.
                                                                   Similarly, SWF_2 is chosen when searching for a
                                                                   “flexible” screening. As a result, CxGs act as an interface
                                                                   to make decisions to choose SWF from the SWF
                                                                   repository.

                                                                   Discussion: It is normal to expect nothing from the
                                                                   repository, scientist could move to the next phase to start
                                                                   workflow design from scratch.

                                                                   Workflow Designing
          Figure 3: Elements in Contextual graph                   Motivation: During workflow design, a certain degree of
                                                                   freedom is given to the user to execute a workflow by
Workflow Searching                                                 offering multiple alternative execution paths. Classical
Motivation: Before the workflow design, context                    workflow systems reduce the degree of flexibility by
behaves as an interface to determine which SWF should              offering powerful design constructs (e.g., start, if/else,
be chosen from a library of SWFs, or a SWF repository.             repeat until, parallel execution, end), in which decision-
In this case, a scientist plays a role as a context provider       making is always measured by a decision node
to guide the choice of the right SWF model according to            accompanying with a numerical value. However, human
current focus and context at hand, so as to largely match          decision is so complex that a numerical decision is less
what the scientific hypotheses indicate.                           descriptive than a simple question. As a result, we
                                                                   describe execution paths of workflow in contextual graphs
Realization approach:                                              (CxGs) which model contextualized information (CEs)
    Scientist firstly searches a SWF from a SWF                   and their dependencies. In a contextual graph, the most
     repository, using keywords which could best                   appropriate execution path could be selected from those
     describe their hypotheses and are coherent with the           encoded during the execution time to address the context
     context at hand.                                              at hand.
    If the pre-existing SWF is exactly what they want,
     the scientist could skip workflow design phase and            Realization approach:
     just replace with their own parameters for workflow               Firstly, it is necessary to know all the current
     execution directly.                                                instances of the CEs at the moment of the
    Otherwise if it is similar to their needs, slight                  application of the workflow. An instantiation is the
     modifications will be carried out shortly in the                   value that a contextual element can take for a
     workflow design.                                                   specific instantiation of the focus at hand.
                                                                       Then, a group of contextualized information is
                                                                        generalized as a set of CEs.
                                                                       CEs are then formalized in a contextual graph by
                                                                        their dependencies. The contextual graph is ready
                                                                        for the workflow execution, when a SWF instance
                                                                        corresponds to a specific execution path under the
                                                                        instantiation of context. In CxG, the execution path
                                                                        is a sequence of actions, connected by the
                                                                        instantiation of the selected contextual elements.

                                                                   Example: In Figure 5, a scientist designs the workflow of
Context graph: virtual screening on protein PAc                    protein preparation as a contextual graph with a set of
1: Is the protein rigid or flexible?                               contextual elements (CE1 and CE4) and their execution
 Rigid 2: Activity: perform first rigid screening                  dependencies. The possible execution paths are controlled
 Flexible 3: Activity: perform second flexible screening           by the value of each contextual element. For example, the
4: analyze the result                                              instantiation of CE1 (i.e., value of CE1= “Yes”) and CE4
                                                                   (i.e., value of CE4= “Yes”) leads to the execution path of
Figure 4: (Left) Contextual graph of virtual screening on          “1→2→4→11→5→6→9”.
  H5N1 protein; (Right) Choosing one SWF from two
              SWFs (SWF_1 and SWF_2)




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                    CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




                                                                    optimize the protein) is invoked as a new SWF
                                                                    component. Furthermore, the contextual graph is updated
                                                                    along with the change of CEs, and it is necessary to record
                                                                    such update in a knowledge base for the sake of workflow
                                                                    sharing, which will be discussed in the next section.



    Contextual graph: protein preparation (old)
     1: Can you find the protein by yourself?
        Yes 2: download it from "Protein Data Bank"
        No 3: ask for help until you get the protein
     4: Do you need to do "protein preparation"?
        Yes 11: enter parameters during "protein preparation"
              5: Activity: remove unrelated molecules
              6: Activity: add hydrogen and charge
              9: store the protein prepared in the database           Figure 6: Contextual graph: protein preparation (new)
      No
                                                                    Discussion: It would be a risk of incoherence between the
  Figure 5: Contextual graph: protein preparation (old)             running workflow instance and results. For example,
                                                                    when you made a decision two minutes ago and the
Discussion: Describing a completely set of all possible             contextual graph chooses an execution path for the
execution paths during workflow design might be either              workflow. But later, right before the workflow execution,
undesirable or impossible (Schonenberg et al., 2008). For           a new context arrives to urge the adaptation of a new
example, a certain number of possible execution paths are           contextual graph.
unknown before execution. As a result, late-modelling
(Han et al., 1998) could enable to make sub-model                   Workflow Publishing
dynamically defined during execution.                               Motivation: If executed successfully, the scientist then try
                                                                    to analyse the results generalized by workflow execution.
Workflow Execution                                                  Type of result analysis includes: 1) evaluate data quality
Motivation: Scientists frequently re-execute the scientific         (e.g., does this result make sense?), 2) examine execution
workflow by adding or ignoring portions of workflow                 traces and data dependencies (e.g., which results were
realized at design time. Context should support the                 “tainted” by this input dataset?), 3) debug runs (e.g., why
assembling of SWF components, which must be                         did this step fail?), or 4) simply analyse performance (e.g.,
recompiled each time when a new context arrives (i.e., a            which steps took the longest time?). After the result
contextual element takes a new instance). As a result, a            analysis process, it is possible to re-design and re-execute
new execution path, or even a new contextual graph will             the workflow iteratively until the new context is addressed.
be inserted or removed when SWF evolves along with its              Incremental knowledge acquisition should be proceeded
context.                                                            to make contextual graph growing to be more efficient.
                                                                    Furthermore, one of the motivations what scientists are
Realization approach:                                               counting on SWF is the sharing, reproduction,
    Each time a new instantiation of a CE occurs, the              transformation, and evolution of the “old” SWF to be a
     contextual graph is re-executed, and the SWF is                brand “new” one. It is expected to enable sharing of SWFs
     recompiled for generating a new SWF instance for               according to their contexts of use. In this circumstance,
     execution.                                                     the context defines the status of the knowledge and also
    If the scientist wants to re-design the workflow by            maintains the relationship between different kinds of
     adding or ignoring portion of SWF, they first stop             knowledge.
     the current workflow execution.
    Then, a new group of contextualized information,               Realization approach:
     including the information representing the workflow                A SWF repository is build up to document
     changes, should be generalized as a new set of                      workflows with their contexts of use.
     contextual elements.                                               When workflow is re-executed, the contextual graph
    If a CE with the following activities/actions is added              is adapted incrementally to trace the workflow
     or ignored, a new contextual graph is produced to                   flexibility. Once a new contextual graph is
     address the new focus.                                              generated, add it as a new scenario to SWF
                                                                         repository.
Example: Figure 6 is inherited from Figure 5. During the                Conscientious users might partition the workflow
execution phase, the scientist finds something wrong with                into coherent fragments and publish them.
the intermediate result, because he doesn't take into
account whether the protein is flexible or rigid. So he             Example: Once a contextual element is modified, a new
decides to stop the current execution and re-design the             CxG is created to address the new focus and its context.
experiment. As a result, a new contextual element CE7 (Is           Drawn from Figure 6, Figure 7 shows a new contextual
it a rigid or flexible screening?) is added. When the value         graph to be added in a SWF repository for future sharing
of CE7 is “flexible screening”, Activity13 (Activity:               with other scientists.


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                      CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




                                                                         Context has been considered as a key element to support
                                                                       decision making in human centered processes for a long
                                                                       time (Brézillon, 2003; Brézillon, 2010). To address a
                                                                       coherent formalism of context, Sowa (1984) proposes
                                                                       conceptual graphs with their mechanisms of aggregation
                                                                       and expansion. Then, Sowa (2000) introduces a way to
                                                                       manage the context in conceptual graphs. Brézillon (2005)
                                                                       presents a simpler formalism of Contextual Graphs (CxGs)
Contextual graph: protein preparation (new)
                                                                       for representing context. Compared with other approaches,
 1: Can you find the protein by yourself?
    Yes 2: Download it from "Protein Data Bank"
                                                                       CxGs formalism is good at describing decision making in
                                                                       which context influences the line of reasoning.
    No     3: Ask for help until you get the protein
                                                                          In the implementation level, a number of applications
 4: Do you need to do "protein preparation"?
                                                                       exist for preparing formal representation of context.
     Yes 11: Enter parameters during "protein preparation"
                                                                       McCarthy (1993) formalizes contexts as formal objects,
            5: Activity: remove unrelated molecules
                                                                       and the basic relation is ist(c,p). It asserts that the
            6: Activity: add hydrogen and charge
            7: Is it a rigid or flexible screening?
                                                                       proposition p is true in the context c, where c is meant to
                                                                       capture all that is not explicit in p that is required to make
                Rigid
                                                                       p a meaningful statement representing what it is intended
                Flexible      13: Activity: optimize the protein
                                                                       to state. Formulas ist(c,p) are always asserted within a
            9: store the protein prepared in the database
                                                                       context, i.e., something like ist(c', ist(c,p)): c': ist (c, p).
     No
                                                                       Sharma (1995) gives a list of desirable properties for
  Figure 7: Contextual graph: protein preparation (new)                contexts in a formal language and distinguishes four
                                                                       approaches for formalizing contexts: (1) incrementing
                                                                       arity; (2) variation on implication; (3) modal operator
Discussion: Encourage sharing of scientific workflow
                                                                       forms; and (4) syntactic treatment. Based on McCarthy's
with its context, would make it as a complementary of
                                                                       work on context logic, Farquhar et al. (1995) present an
paper-based publications. In such a case, scientific
                                                                       approach to integrating disparate heterogeneous
workflow would be archived along with paper-based
publications. However, the quality of sharing data and                 information sources.
                                                                          In Table 1, we compare various approaches to model
workflow becomes a new question.
                                                                       decision making in workflow, as implementation of
                                                                       “Exclusive Choice workflow pattern” (van de Aalst &
Summary
                                                                       Hofstede, 2003).
   Contextual graphs are a formalism of representation
allowing the description of decision making in which                      Table 1: Comparison of various implementations of
context influences the line of reasoning (e.g. choice of a                       “Exclusive Choice workflow pattern”
method for accomplishing a task). The advantage of
contextual graphs relies on that: (i) CxGs provide
naturally learning and explanation capabilities in the                 Approach              Decision     Decision     Decision
system; and (ii) CxGs allow a learning process for                                           Element      Value        Type
integrating new situations by assimilation and                         BPEL                  ,        Condition Numerical
accommodation. In short, the notion of context is made                 (Zhang      et   al.,                  value
explicit during the four phases of scientific workflow                 2008)
lifecycle by contextual graphs. Contextual Graphs
formalism has been already used in different domains                   CxG               Contextual Value            of Any value
such as medicine, incident management on a subway line,                (Brézillon, 2005) Element    CE
road sign interpretation by a driver, computer security,               UML              Decision          Condition Numerical
psychology, cognitive ergonomics, etc.                                 (Courtney, 2001) Node                        value
                      Related Works                                    Petri-net             Exclusive    Arc        Numerical
                                                                       (Tabak et        al., choice       expression value
Various approaches, such as BPEL (Zhang et al., 2008),
                                                                       1985)
UML (Courtney, 2001), Petri-net (Tabak et al., 1985), are
proposed to address the issue of workflow flexibility by
getting user involved in representing decision-making.                   By comparison, Contextual Graphs plays an equivalent
Applications (Yu et al., 2005; Hey et al., 2009) have                  role to other approaches for representing decision making.
proven the significance of current systems to handle                   Furthermore, the advantage of contextual graphs embraces:
numerical decision-making as control-flow functions,                   (1) multiple representations of decision making, not only
such as “wait 30 second, and then proceed the next task”,              with a numerical value, but also with any kind of answers
“if the value is greater than 5 then execute the task_A, else          to questions to get scientists involved in a local decision-
execute the task_B”. However, it becomes an obstacle to                making process; (2) it is directly readable (e.g. generally
manage the common but important decisions, such as “are                something as “If the contextual element C has the value
you satisfied with the result?” and “do you need to do the             V1, thus use method M1, and with the value V2 use
protein preparation again”, which is more comprehensive                method M2”); and (3) it is very easy to have an
for scientists.                                                        incremental growth of a contextual graph by addition of
                                                                       contextual elements and branches for representing


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                    CEUR Proceedings 4th Workshop HCP Human Centered Processes, February 10-11, 2011




practices developed by users and not yet known by the                 Context: 5th International and Interdisciplinary
system.                                                               Conference (pp. 55-68 ). Berlin :Springer Verlag.
                                                                    Brézillon, P. and Pomerol, J.-Ch. (2010). Framing
                      Conclusion                                      decision making at two levels. In Respicio, A., F. Adam,
The human-centered processes must be considered at a                  G. Phillips-Wren, C. Teixeira & J. Telhada (Eds.),
global level to deal with the user, the task at hand, and the         Bridging the Socio-Technica Gap in Decision Support
context in which the task is accomplished. Take a flexible            Systems- Challenges for the next Decade. Amsterdam:
scientific workflow for example, scientists could not                 IOS Press.
handle the transferring from hypotheses to discovery in             Chen, Y., & Shoichet, BK. (2009). Molecular docking and
the SWF system without taking into account the context.               ligand specificity in fragment-based inhibitor discovery,
  We propose a solution to introduce contextual graphs in
                                                                      Nature Chemical Biology, 5 (5), 358-364.
the four phases of SWF lifecycle, each of which is                  Claus, B., and Johnson, S. (2008). Grid computing in
expressed in a standard format, including a concrete                  large pharmaceutical molecular modeling, Drug
example in the area of virtual screening. In our application          discovery today, 13(13-14), 578-583.
on virtual screening, we use contextual graphs to model             Courtney, J.F. (2001). Decision making and knowledge
the decision making processes of scientists as a uniform              management in inquiring organizations: toward a new
representation of knowledge, reasoning, and contexts. As              decision-making paradigm for DSS. Decision Support
a result, scientists are closely involved in each phase of          Systems, 31(1), 17–38.
SWF lifecycle to maximize the decision support received             Deelman, E. and Chervenak, A.L. (2008). Data
from the system.                                                      Management Challenges of Data-Intensive Scientific
  We believe that all of data, information and knowledge              Workflows. Proceedings of the 8th IEEE International
should be invoked, assembled, organized, structured and               Symposium on Cluster Computing and the Grid (pp.
situated according to the given focus, and finally be                 687-692), Lyon: IEEE CS Press.
formulated as the chunk of professional knowledge for               Deelman, E. and Gil, Y. (2006). Managing large-scale
scientists to maintain their research sustainability.                 scientific workflows in distributed environments:
  The extension of our work includes the development of               Experiences and challenges. Proceedings of the Second
a prototype interface between scientific workflow system              IEEE International Conference on e-Science and Grid
and contextual graphs. Representing and making                        Computing (pp. 144), Washington: IEEE Computer
“context” explicit in SWF system by contextual graph                  Society.
would enhance workflow flexibility by formalizing                   Fan, X. et al. (2010). Context-oriented scientific
scientists' research, strategies, and customization                   workflow system and its application in virtual
information, where elements of knowledge, reasoning and               screening. In Respicio, A., Adam, F., Phillips-Wren, G.,
contexts are represented in a uniform way.                            Teixeira C., and Telhada J. (Eds.). Bridging the Socio-
                                                                      Technical Gap in Decision Support Systems-
                                                                      Challenges for the next Decade (pp. 335-345).
                  Acknowledgments                                     Amsterdam: IOS Press.
This work is supported by grants from National Natural              Farquhar, A, Dappert, J, Fikes, R and Pratt, W. (1995).
Science Foundation of China (90912003, 60773108,                      Integrating information sources using context logic
90812001, 61011130212), Centre national de la                         (Tech. Rep. KSL-95-12). Palo Alto, California: Stanford
recherche scientifique (Researcher exchange project with              University, Knowledge Systems Laboratories.
NSFC 2010), and Région Ile-de-France (CP10-201), and                Gil, Y., Deelman, E., Ellisman, M., Fahringer, T., Fox G.,
by scholarships from China Scholarship Council                        Gannon, D., Goble, C., Livny, M., Moreau, L., Myers, J.
(2008618047), and Égide (690544G).                                    (2007). Examining the Challenges of Scientific
                                                                      Workflows. Computer, 12(40), 24-32.
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