=Paper= {{Paper |id=Vol-1287/lanmr2014_paper_1 |storemode=property |title=Knowledge Representation for Development of Collaborative Applications |pdfUrl=https://ceur-ws.org/Vol-1287/lanmr2014_paper_1.pdf |volume=Vol-1287 }} ==Knowledge Representation for Development of Collaborative Applications== https://ceur-ws.org/Vol-1287/lanmr2014_paper_1.pdf
         Knowledge Representation for the Development of
                  Collaborative Applications

    Mario Anzures-García1, Luz A. Sánchez-Gálvez 1, Miguel J. Hornos2, and Patricia
                              Paderewski-Rodríguez2
    1
        Facultad de Ciencias de la Computación, Benemérita Universidad Autónoma de Puebla,
            Avenida San Claudio y 14 Sur, Ciudad Universitaria. 72570 Puebla, México
           2 Departamento de Lenguajes y Sistemas Informáticos, E.T.S.I. Informática y de

         Telecomunicación, Universidad de Granada, C/ Periodista Saucedo Aranda, s/n,
                                      18071 Granada, Spain.



         Abstract. The workflow to develop collaborative applications should be highly
         adaptable to frequent organizational changes. In order to increase the adaptability
         of workflow, an ontology-based workflow model is proposed. This model
         represents the set of steps —along with their order of execution— performed by
         different entities for developing this kind of applications. Ontology is one of the
         strategies for the structured representation of a chosen knowledge domain in a
         formal way, helping to remove ambiguity and redundancy, detecting errors, and
         allowing automated reasoning. In this work, the ontologies are considered as
         models to represent knowledge. A case study is presented in order to show the
         use of Knowledge-based Workflow Model for Collaborative Applications.
         Palabras Clave: Ontology, Collaborative Application, Workflow Model,
         Knowledge Representation, Knowledge-based Workflow Model.



1       Introduction

   Ontology provides an ideal solution, for it represents the domain knowledge using
description logic symbols, which allows specifying it in a simple, readable way for both
humans and machines; as well as performing a much deeper reasoning by means of
machines. It facilitates a knowledge base to provide semantic, common understanding,
communication, and shared knowledge on the domain of interest, and a knowledge
reasoning carrying out an inference process to reach to conclusions on such a base, by
means of a reasoner, inference rules, and query languages.
   Collaborative applications must provide an appropriate infrastructure to back up
group work and support the dynamic structure of the organizations in runtime. In such
a way that they can represent inherent knowledge in the applications that support groups
of people engaged in a common goal, and provide an interface for a shared
environment. This paper, tries to capture the resulting knowledge in the development
of such applications so, it proposes an ontology-based workflow model named
workflow ontology to develop collaborative applications. This workflow ontology
allows representing all the necessary symbols in order to specify the elements for
building this type of applications. These symbols make up a knowledge base, which
allows to reason and draw conclusions; to generate new knowledge in collaborative
domain, using reasoner, inference rules and query languages. The rest of the paper is
organized as follows: Section 2, describes briefly the ontology-based knowledge;
Section 3, explains the inherent knowledge in the collaborative applications; Section 4,
presents the workflow model for collaborative applications and a case study focused on
academic virtual space; Section 6, outlines the conclusions and future work.


2    Ontology-based knowledge

In recent years, the use of ontologies has extended in diverse areas such as medicine
[1]; bioinformatics [2]; groupware [3, 4]; mainly, because they allow a formal explicit
specification of a shared conceptualization of certain domain of interest.
Conceptualization refers to an abstract model of some knowledge in the world through
the identification of relevant concepts of this. Explicit specification, means that the type
of concepts used and the constraints on their use are explicitly defined. Formal, reflects
the fact that the ontology should be machine-readable. Shared, represents the notion
that an ontology captures consensual knowledge that is not reserved to some individual,
but it is accepted by a group. So, it is said that ontology establishes the vocabulary used
to describe and represent domain knowledge to facilitate machine reasoning. The
domain knowledge, describes the main static information and the objects of knowledge
[5]. According to Gruber [6], domain knowledge in ontologies can be formalized using
four kind of components: concepts, relations, axioms and instances.
   The OWL representation [7] facilities are directly based on Description Logics [8].
This basis confers upon OWL a logical framework, including syntax and model-
theoretical semantics, allowing a knowledge representation language capable of
supporting a knowledge base, and a practical, effective reasoning. Protégé is used in
order to develop ontologies with OWL to provide graphical interfaces that facilitate the
knowledge representation and reasoning. Protégé is an engineering tool open source
ontology and a knowledge-based framework, which is widely used due to its scalability
and extensibility with lots of plugins; to facilitate inference knowledge through
reasoners, query languages, and rules. Therefore, it can be concluded that ontologies
are an ideal solution for knowledge representation and reasoning, since it provides a set
of symbols through a formal and structured vocabulary.


3     Knowledge in collaborative applications

A collaborative application focuses on supporting group work to achieve a common
goal by providing a shared workspace. For this reason, the knowledge is the result of a
group interaction and its adaptation on application, i.e. depends on:
 Group, which carries out a set of tasks to achieve a common goal through a shared
    environment. Consequently, the group should have a suitable Group
    Organizational Structure (GOS). This is ruled by the Session Management
    Policy —SMP— that establishes the same [9]. The SMP defines a hierarchical or
    not-hierarchical GOS by means of Roles that users can play. These roles establish
    the set of Rights/Obligations (R/O) and Status (St) within the group, as well as
    the Tasks that can be carried out to accomplish a common goal. The Task is
    composed of Activities, which use the prevailing shared Resources [10]. The GOS
    specification provides the Knowledge about how the interaction among users is
    carried out; what Roles are involved in the group; what Task is performed by each
    Role, and what Resources are used to achieve a goal. This Knowledge facilitates
    the basic elements of a collaborative application.
   Interaction, requires: A session, shared workspace where a group will interact. A
    notification process that provides the users with the necessary information to
    support the group awareness,—users are aware of another member’s presence in
    the session, and of the actions that each one of them is carrying out—; and supplies
    a common context on which the activities of the group are performed, and where
    the information of the shared resources is stored; thus, creating a group memory to
    provide understanding and reasoning about the collaborative process. A
    concurrency process that ensures the consistency of the data being shared;
    providing collaborating users with dynamically-generated temporary access and
    permissions, to reduce racing conditions, and to guarantee mutually exclusive
    resource usage. These permissions depend on the GOS established and on the lock
    mechanism. So, the interaction knowledge is supplied by concurrency, awareness,
    and memory group, in such a way that the common context helps avoiding
    surprises by reducing the probability of conflicts in the group established [11].
   Application, presents the Views that are user interfaces allowing interaction
    between the users and the application. There are three Views: Information View
    (IV) which is related to individual information; the Participant View (PV) that is
    associated with group awareness; and the Context View (CV) which is connected
    to group memory. The application is made up into phases [12], where each phase
    is defined as a global description of the tasks that are active. Therefore, the
    knowledge is supplied via the IV, PV, and CV, allowing to show the interaction
    between users and the application; as well as by means of phases which constrain
    the users who can participate in accordance with the roles they are playing.
   Adaptation [13]; adjusts the Views in accordance to changes triggered by
    notification, in such a manner that the application shows the most recent updates
    although preserving its functionality. Accordingly, it is necessary to monitor the
    changes in the session using a detection process; in the case of an adaptable
    process (when the adaptation is carried out by direct intervention of the user) in a
    non-hierarchical GOS the pre-adaptation stage is performed. This process
    accomplishes an agreement, where all users have to reach a consensus on whether
    an adaptation process should be performed by means of a Voting Tool, which
    offers several kinds of agreements such as the agreement based on the majority
    vote, the one based on a maximum or minimum value, etc. In the case of an
    adaptive process (when the adaptation is automatically performed) or the users
    have agreed to make the adaptation, an adaptation flow process is performed.
    When an adaptation flow cannot be completed, a reparation process is invoked,
    —which returns each component to its previous state— then, users are notified that
    this adaptation process cannot be achieved. Knowledge is related to modifying
    one or several application components, in order to change exclusively that part of
    the application which did not fit the features of the new scenario.
   The aforementioned is derived from the architectural model (see Figure 1) presented
in [10] that is the result of the study and review of several tools or frameworks (such as
Groupkit [14], ANTS [15], and SAGA [16]), architectures (e.g., Clock [17], and Clover
[18]), and methodologies (AMENITIES [19], ClAM [3], and TOUCHE [4]). Where
the different concepts and terms above mentioned (such as group, role, task, activity,
resource, session, notification, concurrency, shared user interface, phase, adaptation,
etc.), have been applied to design and develop collaborative applications. All these
concepts and terms will be used as symbols, which are part of workflow ontology for
the development of collaborative applications.
                                      Pre-Adaptation            Votation            Adaptation Stage
                        ADAPTATION        Stage                  Tool                              Reparation
                          LEVEL
                                                                                   Adaptation
                                       Detection           Agreement                 Flow



                       APPLICATION                                             Participant        Context
                                                         Information
                          LEVEL         Phase
                                                             View                 View             View



                        INTERACTION    Session                                             Concurrence
                           LEVEL                               Notification


                                          Group
                                       Organizational               User                            Resource
                        GROUP            Structure                                 Task
                        LEVEL
                                             Policy              Role
                                                                                                   Activity
                                                                                Right/
                                                      Status                  Obligation



               Figure 1. Layered architectural model for building groupware



4    A workflow model for collaborative applications

The development of collaborative applications needs to perform a group of coordinated
steps which can be accomplished by means of a workflow. The term workflow typically
refers to coordinated execution of multiple tasks or operations [20]. However,
workflows lack the expressive power to represent the domain knowledge and the
sequence of operations. On the other hand, ontology describes knowledge domain
through concepts, relations, axioms and instances, although ontology does not specify
how these entities should be used and combined.
   Special attention has recently been paid to the development of workflow ontologies,
as the workflow can be built on the ontology. The former defines how the tasks or
operations should be used and combined, and once that it has been represented, it may
be considered a static structure. The latter can symbolize this structure due to its
expressive power. So the ontology is an ideal solution for the workflow representation.
There are several examples of workflow ontologies: it presents a collaborative
workflow for terminology extraction and collaborative modeling of formal ontologies
using two tools Protege and OntoLancs [21]; it allows the development of cooperative
and distributed ontologies, based on dependencies management between ontologies
modules [22]; it shows an ontology-based workflows for ontology collaborative
development in Protégé [23],it presents the combination of workflows with ontologies
to design way formal protocols for laboratories [24], it proposes a workflow ontology
for the preservation of digital material produced by an organization or a file system
[25]. All these works are focused on building workflow ontologies to represent
collaborative work in different areas, however, this paper presents a workflow ontology
to develop collaborative application (see Figure 2) using the architectural model
elements as the ontology vocabulary.
   The Table 1 shows the concepts, relations and axioms of the Workflow Ontology,
which establishes; first, the Application is described; second, the SMP name is stated;
third, the GOS together with all the elements that contain it are defined; fourth, the
Tasks that are part of the Phase and the View are specified; fifth, the Resources that
will be presented on the View; sixth, the IV, PV, and CV that will have the View;
seventh, the Change produced by Activity; eighth, the Notification and Concurrency
(Cc) triggered by Change; ninth, the Resource locked by means of the Cc; tenth, the
Adaptation (Ad) generated through Notification; eleventh, the Adaptation is showed
on View (IV, PV, and CV); twelfth, it outlines both Views and Phases that are part of
the Session, and finally the Sessions that comprise the Application.
Table 1. Workflow Ontology components.
                     Relation                   Domain        Range         Constrain
                                               (Concept)    (Concept)
        establishies inverse: isEstablished   Application      GOS      max cardinality=1
        contains inverse: IsContained             GOS          User     min cardinality=2
        isGoverned inverse: governs               GOS         Policy    max cardinality=1
        determines inverse: isDetermined         Policy        Role     min cardinality=1
        indicate inverse: isIndicated             Role        Status    max cardinality=1
        designates inverse: isDesignated         Status        R/O      min cardinality=1
        signpost inverse: isSignposted            R/O          Task     min cardinality=1
        isFormed inverse: formed                  Task       Activity   min cardinality=1
        uses inverse: isUsed                    Activity     Resource   min cardinality=1
        has inverse: isHave                      Phase         Task     min cardinality=1
        isDisplayed inverse: display              Task        View      min cardinality=1
        exhibits inverse: isExhibited            View        Resource   min cardinality=1
        is                                     IV/PV/CV       View      min cardinality=1
        produces inverse: is Produced           Activity     Change     min cardinality=0
        triggers inverse: isTriggered           Change     Notification min cardinality=0
        triggers inverse: isTriggered           Change     Concurrency min cardinality=0
        locks inverse: isLocked               Concurrency    Resource   min cardinality=1
        generates inverse: isGenerated        Notification Adaptation min cardinality=1
        shows inverse: isShowed                  View       Adaptation min cardinality=1
        is_part_of                               View        Session    min cardinality=1
        is_part_of                               Phase       Session    min cardinality=1
        composite                             Application    Session    min cardinality=1

A case study is an Academic Virtual Space (AVS) which provides the students with a
shared workspace to simplify their access to the course material previously loaded by
the professor. The AVS includes two roles: 1) The professor can register himself, create
groups, upload and download files both his and those of the students, publish and
respond to those made by others; and 2) The students, can register themselves in the
shared space and access courses, load and unload files (homework and course materials
that have been uploaded by the teacher), make publications and to reply to them. Thus,
in order to create this workspace only the workflow ontology instances should be
defined (see Table 2). The instances are defined in according to the established steps in
the workflow ontology. These constitute the knowledge base for developing
collaborative applications. Therefore, first, the described Application is AVS; second,
the stated SMP is SMP-AVS; third, the defined GOS is GOS-AVS and the elements
                         play
                                                      indicate


   contains                                                                 designates
                                              determines
                      isGoverned



  establishes                                                                signpost


                                                           has                     isFormed

                     designates
composites
                                        isDisplayed                                      produces    uses
                        designates
                                                                                             locks
                                                                 triggers
     presents

                        exhibits

                                                                            generates
                is          is_showed




                       Figure 2. Workflow Ontology to develop groupware.
that contain the GOS-AVS are showed in the Table 2; the fourth, two phases are
specified along with their tasks that are part of the Phase, as well as the Views are
designated; fifth, the Resources on each View are presented; sixth, the IV, PV, and CV
that will have the View are showed; seventh, the produced Change by Activity are
revealed in the Notification Colum of the Table 2; eighth, the triggered Cc by Change
is indicated by Yes in the Cc column (Y); ninth, the Cc column presents Y, when a
Resource is locked; tenth, the generated Adaptation is displayed in the Ad column;
eleventh, the showed Adaptation on View is specified with Y in IV, PV, and CV;
twelfth, the Views and Phases of the Session are exhibited, and finally the Sessions
that comprise the Application. When Table 2 is constructed, and the GOS elements are
already defined, it is possible infer, for example: The tasks of each phase and view; the
presented resources in each view, the produced changes by each activity, the activated
concurrency by change, etc. This inference is very important when a collaborative
application has been developed. Furthermore, the AVS knowledge base can be used in
another applications, which focus in academic environment and requires two roles
(Teacher and Student). In this a manner, it will be possible to reduce time and costs in
the development of collaborative applications.


5    Conclusions and Future Work

This paper has presented a workflow model for developing collaborative applications
using the inherent knowledge of the integrated elements —group, interaction,
application and adaptation— necessary to build this applications. These elements are
the ontology concepts, and present a set of constrains, that guide and facilitate the
development of this applications. Developing a formal and structured knowledge base,
which allows building any collaborative application, defining its instances on ontology.
Furthermore, in order to simplify and facilitate an ontology description, a specification
table is proposed, in such a manner that any individual may be able to develop a
collaborative application by means on this table.
   The future work will aim to specify a methodology to develop collaborative
application, starting with the workflow ontology described in this article.


References

1. Jovic, A., Prcela, M, and Gamberger, D. Ontologies in Medical Knowledge Representation.
   In Proceedings of the 29th Int. Conf. on Information Technology Interfaces, pp. 25-28, (2007)
2. Stevens, R., Goble, C.A., and Bechhofer, S. Ontology-based knowledge representation for
   bioinformatics. Briefings in Bioinformatics, Vol. 1-4, pp. 398-414, (2000)
3. Molina, A.I., Redondo, M.A., Ortega, M., and Hope, U. ClAM. A methodology for the
   development of groupware user interfaces. Journal of Universal Computer Science (2007)
4. Penichet, V., Lozano, M., and Gallud. J. An Ontology to Model Collaborative Organizational
   Structures in CSCW. In Engineering the User Interface, Springer, pp.127-139, (2008)
5. Schreiber, G., Akkermans, H., Anjewierden, A., Hoog, R., Shadbolt, N., Van de Velde, W.,
   Wielinga, B. Knowledge engineering and management. The KADS Methodology. (1999)
             Tabla 2. Knowledge Base of AVS.
                                                                                                       Se_
Rol     St      R/O           Task                  Activity                   Resource                       View (V)   Phase            Notification            Cc        IV      PV   CV      Ad
                                                                                                      ssion
                                           Capturing Login            Label (L), Text Box (TB)                                              NOT (N)                N      YES (Y)   N    N        N
                                           Capturing Password         L, TB                                                                    N                   N        Y       N    N        N
Profe                                      Repeat Password            L, TB                                                                    N                   N        Y       N    N        N
_ssor                                      Capturing First Name       L, TB                                                                    N                   N        Y       N    N        N
             Accessing       Register
 (P),   1,                                 Capturing Last Name        L, TB                                    Regis_                          N                   N        Y       N    N        N
                the           User
Stu_    2                                  Capturing Facebook         L, TB                                    tering                          N                   N        Y       N    N        N
             Application                                                                                                 Acce_
dent                                       Capturing Twitter          L, TB                                                                    N                   N        Y       N    N        N
                                                                                                                         ssing
 (S)                                       Capturing e-mail           L, TB                                                                    N                   N        Y       N    N        N
                                           Uploading Picture          Browse Button(BB), File(Fi)                                              N                   N        Y       N    N        N
                                           Send Data                  Register Button (RB)                                        Arriving New User to another   DB & V     Y       Y    Y     TL, SL
             Authentica_                   Capturing Login            L, TB                                   Identi_                          N                   N        Y       N    N        N
        1,                 Authentica
P, S         ting on the                   Capturing Password         L, TB                                   fication                         N                   N        Y       N    N        N
        2                  _ting User
             Application                   Send Data                  RB                                                          User Access (UA) to another    DB & V     Y       Y    Y      UA
                                           Review File                L, TB, Fi                       AVSS                          File Updating to another     DB & V     Y       Y    Y     Fi List
        1,   Managing       Managing       Creating Delivery Date     Calendar                                                      Date Updating to another     DB & V     Y       Y    Y      Date
P, S                                                                                                           Task
        2     Task          User Task      Uploading Task             BB, Fi                                                        Task Updating to another     DB & V     Y       Y    Y      Task
                                           Downloading Task           BB, Fi                                                      Downloaded Task to another     DB & V     Y       Y    Y     Task Fi
        1,     Writing       Sending
P, S                                       Commenting on the Wall     TB, Button Send (BS)                                        Updating Message to another    DB & V     Y       Y    Y    Messages
        2     Comment       Comment
                                                                                                                         Shared
                                                                      L, Courses List(CL), TB,
                                           Selecting Course                                                              Work_     Selected Course to another    DB & V     Y       Y    Y       CL
                                                                      Combo Box (CB), BS
              Generate       Creating                                                                                    space
 P      1                                  Describing Course          L. TB, BS                                                   Described Course to another    DB & V     Y       Y    Y       Course
               Group          Group                                                                            Group
                                           Choosing Hours             CL, TB, CB, BS                                                Chosen Hours to another      DB & V     Y       Y    Y        Date
                                           Creating Group Password    L, TB, BS                                                    Created Group to another      DB & V     Y       Y    Y         GL
                                                                      L, Teachers List(TL), Student                               Selected Teacher to another    DB & V     Y       Y    Y         TL
             Register in   Enroll in the   Select Teacher, Select
 S      2                                                             List(SL), Groups List(GL),                                   Selected Group to another     DB & V     Y       Y    Y    It shows G
               Group         Group         Group, and Select Course
                                                                      CL, BS                                                       Enter of User to the Group    DB & V     Y       Y    Y       Group
6. Gruber, R. A translation approach to portable ontology specification. Knowledge
    Acquisition. Vol. 5, pp. 199-220, (1993)
7. Horrocks, I., Patel-Schneider, P.F., and van Harmelen, F. From SHIQ and RDF to OWL: The
    making of a web ontology language. J. of Web Semantics, Vol. 1-1, pp. 7-26, (2003)
8. Baader, F., Calvanese, D., McGuinness, D., Nardi, D., and Patel-Schneider, P. F. editors. The
    Description Logic Handbook: Theory, Implementation and Applications. Cambridge
    University Press, (2003)
9. Anzures-García, M., Sánchez-Gálvez, L.A., Hornos, M.J., and Paderewski-Rodríguez, P.
    Ontology-Based Modelling of Session Management Policies for Groupware Applications.
    Lecture Notes in Computer Science, Vol. 4739, pp. 57–64, Springer, Heidelberg, (2007)
10. Anzures-García, M., Sánchez-Gálvez, L.A., Hornos, M.J., and Paderewski-Rodríguez, P.
    SAMCA: Service-based architectural model for collaborative applications. In Proc. 15TH
    International Conference on Software Engineering and Applications (2011)
11. Anzures-García M., Sánchez-Gálvez L.A., Hornos M.J. & Paderewski, P. Methontology-
    based ontology representing a service-based architectural model for collaborative
    applications. Advances in Soft Computing Algorithms. RCS, Vol. 54, pp. 77-90, (2011)
12. Anzures-García, M., Sánchez-Gálvez, L.A., Hornos, M.J., and Paderewski-Rodríguez, P.
    Service-based access control using stages for collaborative systems. Advances in Computer
    Science and Engineering. Research in Computing Science, Vol. 42, pp. 311-322, (2009)
13. Anzures-García, M., Sánchez-Gálvez, L.A., Hornos, M.J., and Paderewski, P. Security and
    adaptability to groupware applications using a set of SOA-based services. Advances in
    Computer Science and Engineering. RCS, Vol. 45, pp. 279-290, (2010)
14. Roseman, M., and Greenberg, S. Building Real-time Groupware with GroupKit, a
    Groupware ToolKit. ACM Trans. Computer-Human-Interaction, Vol. 3, 66-106, (1996).
15. García, P., and Gómez, A. ANTS Framework for Cooperative Work Environments. IEEE
    Computer Society Press, Vol. 36, 3 Los Alamitos, CA, USA, pp. 56-62, (2003).
16. Fonseca, B., and Carrapatoso, E. SAGA: A Web Services Architecture for Groupware
    Applications, In Proc. of the CRIWG, LNCS 4154, Springer-Verlag, pp. 246-261, (2006).
17. Graham, T.C.N., and Urnes, T. Integrating Support for Temporal Media in to an Architecture
    for Graphical User Interfaces. Proc. of the International Conference on Software Engineering
    (ICSE'97), ACM Press, Boston, USA, pp. 172-182, (1997).
18. Laurillau, Y., and Nigay, L. Clover Architecture for Groupware. Proc. of the ACM
    Conference on CSCW. New Orleans, Louisiana, USA, pp. 236-245, (2002)
19. Garrido, J. L., Gea, M., Padilla, N., Canas, J.J., and Waern, Y. AMENITIES: Modelo de
    entornos cooperativos. In I. Aedo, P. Díaz & C. Fernández (eds.), Actas del III Congreso
    Internacional Interacción Persona-Ordenador, pp. 97-104, (2002)
20. Fischer, L. Workflow Handbook. Future Strategeis Inc., Lighthouse Point, FL (2004)
21. Gacitua, R.; Arguello-Casteleiro, M.; Sawyer, P.; Des, J.; Perez, R.; Fernandez-Prieto, M.J.;
    Paniagua, H., A collaborative workflow for building ontologies: A case study in the
    biomedical field. Research Challenges in Information Scienc. pp.121-128 (2009)
22. Kozaki, K., Sunagawa, E., Kitamura, Y. and Mizoguchi, R. A Framework for Cooperative
    Ontology Construction Based on Dependency Management of Modules. Vol. 292 of CEUR
    Workshop Proceedings, pp. 33-44. CEUR-WS.org,(2007)
23. Sebastian, A., Noy, N.F., Tudorache, T., Musen, M.A. A Generic Ontology for Collaborative
    Ontology-Development Workflows. Proceedings of the 16th international conference on
    Knowledge Engineering: Practice and Patterns, (2008)
24. Maccagnan, A., Riva, M., Feltrin, E., Simionati, B., Vardanega, T., Valle, G., Cannata, N.
    Combining ontologies and workflows to design formal protocols for biological laboratories,
    Automated Experimentation, Vol. 2-3, (2010)
25. Mikelakis, M., Papatheodorou, C. An ontology-based model for preservation workflows.
    In Proceedings of the 9th International Conference on Digital Preservation, (2012)