=Paper=
{{Paper
|id=None
|storemode=property
|title=Visualizing and Editing Ontology Fragments with OWLGrEd
|pdfUrl=https://ceur-ws.org/Vol-932/paper5.pdf
|volume=Vol-932
|dblpUrl=https://dblp.org/rec/conf/i-semantics/LiepinsCS12
}}
==Visualizing and Editing Ontology Fragments with OWLGrEd==
<pdf width="1500px">https://ceur-ws.org/Vol-932/paper5.pdf</pdf>
<pre>
                   Proceedings of the I-SEMANTICS 2012 Posters & Demonstrations Track, pp. 22-25, 2012.
                   Copyright © 2012 for the individual papers by the papers' authors. Copying permitted only
                   for private and academic purposes. This volume is published and copyrighted by its editors.




          Visualizing and Editing Ontology Fragments with
                           OWLGrEd
                          Renars Liepins
*, Karlis Cerans
, Arturs Sprogis**

                 Institute of Mathematics and Computer Science, University of Latvia
                     { Renars.Liepins, Karlis.Cerans, Arturs.Sprogis}@lumii.lv



          Abstract. The OWLGrEd ontology editor allows graphical visualization and
          authoring of OWL 2.0 ontologies using a compact yet intuitive presentation that
          combines UML class diagram notation with textual Manchester syntax for class
          expressions. Here we show, how to integrate OWLGrEd with ontology module
          mechanism from OWL API to obtain on-demand ontology fragment
          visualization that is essential for many existing large ontologies that do not fit
          in a single reasonably perceivable UML class diagram.
          Keywords: OWL ontologies, visualization, UML/OWL profile, OWLGrEd,
          ontology decomposition, ontology modules



1 Introduction

Intuitive ontology visualization is a key for their learning, exchange, as well as their
use in conceptual modeling and semantic database schema design. A number of tools
and approaches exist for rendering and/or editing OWL [1] ontologies in a graphical
form, including UML Profile for OWL DL [2], ODM [3], TopBraid Composer [4],
Protégé [5] plug-in OWLViz [6] and OWLGrEd [7,8]. The approaches of [2,3,7,8]
use UML [9] class diagrams to visualize OWL ontologies. This is achieved by
visualizing an independent hierarchy of ontology classes and then structuring the data
and object property visualizations along the property domain and range classes. The
OWL ontology constructions not having direct UML counterparts (e.g. class expressi-
ons, properties with more than one domain assertion, sub-property relations etc.) are
usually handled by some auxiliary means in the notation and the editor. OWLGrEd
uses textual OWL Manchester syntax [10] for class expressions where the graphical
notation is not available or is not desired thus allowing compact and comprehensible
presentation of up to medium-sized ontologies within a single diagram.
   The main focus of this demo is on using the compact UML-style notation, offered
by OWLGrEd, on large ontologies that do not fit within any reasonably-sized class
diagram, or whose rendering appears to be too complicated due to a kind of “spider
web” effect produced by many classes and relations. Its key idea consists in splitting
the ontology into meaningful fragments of conceivable size and then visualizing each
of the fragments in a separate diagram .

**
     Partially supported by Latvian 2010.-2013. National Research Program Nr.2 project Nr.5.
*
     Partially supported by European Union via European Regional Development Fund project
     2011/0009/2DP/2.1.1.1.0/10/APIA/VIAA/112.



                                                                 22
Visualizing and Editing Ontology Fragments with OWLGrEd

   OWLGrEd already has the means to partition ontology into sub-diagrams
(fragments) when authoring or reengineering an existing ontology. But there was no
way to automatically partition an ontology that is imported into OWLGrEd for
visualization. In this demo we will present an extension to OWLGrEd visualization
capabilities, that allows automatic partitioning of an ontology into logical fragments.
The addition is based on Automatic Decomposition [11] that was recently
implemented in the OWL API1. The decomposition is based on signatures, i.e. for
each fragment a user selects some entities that should be included in the fragment.
Then the fragment is extended with all the logically relevant axioms for these entities.
Finally all the fragments are rendered graphically in the OWLGrEd editor.
   The demonstration shows (i) working with OWLGrEd tool to render and author
OWL ontologies (ii) OWLGrEd extension to automatically partition ontology into
logical overlapping fragments based on fragment signatures.


2 OWLGrEd Notation and Editor

OWLGrEd1 provides a complete graphical notation for OWL 2 [1], based on UML
class diagrams. We visualize OWL classes as UML classes, data properties as class
attributes, object properties as associations, individuals as objects and cardinality
restrictions on association domain class as UML cardinalities. It is easy to visualize
also subclass and inverse properties notations. For the full OWL 2 construct coverage
we enrich the UML class diagrams with the new extension notations, e.g. (cf. [7,8]):
        • fields in classes for equivalent class, superclass and disjoint class
   expressions written in Manchester OWL syntax [10];
        • fields in associations and attributes for equivalent, disjoint and super
   properties and fields for property characteristics, e.g., functional, transitive, etc.;
        • anonymous classes containing equivalent class expression but no name (we
   show graphically only anonymous classes that need to have graphic representation
   in order to be able to describe other ontology concepts in the diagram);
        • connectors (as lines) for visualizing binary disjoint, equivalent, etc. axioms;
        • boxes with connectors for n-ary disjoint, equivalent, etc. axioms;
        • connectors (lines) for visualizing object property restrictions some, only,
   exactly, as well as cardinality restrictions.
    OWLGrEd provides option to specify class expressions in compact textual form
rather than using separate graphical element for each logical item within class
expression. If an expression is referenced in multiple places, it can optionally be
shown as an anonymous class. An anonymous class is also used as a base for property
domain/range specification, if this domain/range is not a named class.
    Figure 1 illustrates some basic OWLGrEd constructs on a simple mini-University
ontology, including different notation options for EquivalentClasses assertion, object
property restriction and a comment. The notation is explained in more detail in [7].


1
    http://owlapi.sourceforge.net
2
    http://owlgred.lumii.lv/




                                             23
Visualizing and Editing Ontology Fragments with OWLGrEd


         Thing{owl}                                               {disjoint}
      name:string{func}
                                         Person                           AcademicProgram
                              "All persons, including teachers                                             belongsTo
         <<Comment>>                                                  programName:string{<name}
                              and students"
     "All persons,            key = personID
     including teachers       personName:string{<name}                enrolled {>takes o                     includes
     and students"            personID:string[1]                               belongsTo}
                                                                                                 relates        Course
         Professor                                                                                          courseName:string
                          <<disjoint>>                                                                      {<name}
                                                     Student      isTakenBy       takes {<relates} 1..10


      <<equivalent>>          Teacher           isTaughtBy               teaches {<relates} {<>takes}


       AcademicStaff            PermanentTeaching Staff                                              MandatoryCourse
      =Teacher                                                                 teaches some [1..*]
                              <teaches some MandatoryCourse



    Fig. 1. Example: OWLGrEd notation for a mini-University ontology

  The OWGrEd editor offers ontology interoperability (import/export) functionality
with the Protégé 4.2 ontology editor [5]. The principal OWLGrEd usage ways are:
  - ontology authoring (create and edit an ontology in OWLGrEd, then export it to
       Protégé to analyze and possibly submit it to other ontology processing tools)
  - ontology visualization (an ontology that is imported from Protégé is displayed
       graphically to obtain a comprehensible visual view on it).



3 Visualizing Fragments of Ontology

The graphical form is ideal for understanding small ontologies, but for large
ontologies it fast becomes overwhelming because of too many line crossings. For
visualization of the ontology in the form of fragments an issue is to describe the
fragments to be visualized since manual enumeration of all axioms to be included into
a fragment would clearly be infeasible. Recently there has been work on signature-
based automatic decomposition [11] of ontologies that allows specify ontology
modules just in terms of their “core” terms/entities. The decomposition then finds all
the axioms that are logically relevant for the given entities.
   We have extended OWLGrEd editor with the Automatic Decomposition feature. A
user can specify either a single ontology fragment, or a list of fragments covering the
whole ontology that is to be visualized. The automatic decomposition then finds all
the relevant axioms for each specified fragment thus allowing OWLGrEd showing the
fragments visually in a graphical form.
   As an example consider the schema.org ontology. It consists of about 300 classes,
110 object properties, 70 data properties and 310 subclass assertions. The ontology is
clearly too large to be easily perceived as a single diagram. However, it would be
feasible as well as meaningful to visualize fragments of the. For example, in the
Figure 2 is shown a fragment that is centered on entities “Event”, “Product” and
“Person”. Once the user has specified such an entity list, the tool automatically finds
the relevant axioms for these entities and then shows this fragment graphically. It is
possible to specify any number of such fragment signatures at a time and the tool will
create visualization for each of them.



                                                                 24
Visualizing and Editing Ontology Fragments with OWLGrEd

   The experiments we have performed allows us to judge that the offered approach
of combining of the traditional OWLGrEd ontology visualization means with
ontology decomposition techniques would be a useful tool for the semantic
technology community in ontology schema structure representation.

            Thing{owl}   brand                             Product
                                                    model                                                EducationEvent
                         manufacturer
                                        itemOffered productID

                                                                                                          BusinessEvent
                                                                               subEvents
                                                                                       Event
                                                              superEvent
                                                                               endDate
                                                                                                            SportsEvent
                         performers                                            startDate
                         attendees
                                                                      events                               SocialEvent         UserCheckins
                                                                                           performerIn

                                                                                   Person                    VisualArtsEvent     UserLikes
                                                          knows gender
                                                     colleagues birthDate                                     TheaterEvent
                                                      relatedTo jobTitle                                                        UserBlocks
                                                                 deathDate
                                                         follows                                               DanceEvent
                                                         spous e
                                                                                                                                UserTweets
                                                         parents
                                                                                                                 Festival
                                                        siblings

                                                                                                                                UserPageVisits
                                                        children                                            UserInteraction

                         homeLocation
                         alumniOf
                                                                                                             LiteraryEvent
                         workLocation
                                                                                                                               UserDownloads
                         works For                                                                          ChildrensEvent
                         affiliation                                                                                             UserPlays
                         nationality
                         memberOf                      founders                                             MusicEvent
                                                                                                                               UserComments
                                                           editor
                                                          actors
                                                                                                          ComedyEvent
                                            mus icGroupMember                                                                  UserPlusOnes
                                                       illus trator
                                                       producer                                            SaleEvent
                                                         alumni
                                                     employees
                                                                                                          FoodEvent
                                                         director



      Fig. 2. Automatically extracted fragment of schema.org ontology based on a
                        signature “Event, Product, Person”.


References

1. Motik, B; Patel-Schneider P.F; Parsia B.: OWL 2 Web Ontology Language Structural
   Specification and Functional-Style Syntax, 2009
2. Brockmans, S., Volz, R., Eberhart, A., Löffler, P. Visual Modeling of OWL DL Ontologies
   Using UML, Proc. of ISWC 2004, LNCS 3298, pp. 198-213, 2004.
3. ODM UML profile for OWL, http://www.omg.org/spec/ODM/1.0/PDF/
4. TopBraid Composer, http://www.topquadrant.com/products/TB_Composer.html.
5. Protégé 4, http://protege.stanford.edu/
6. OWL Viz, http://www.co-ode.org/downloads/owlviz/
7. Barzdins, J.; Barzdins, G.; Cerans, K.; Liepins, R.; Sprogis, A.: OWLGrEd: a UML Style
   Graphical Notation and Editor for OWL 2. In Proc. of OWLED 2010, 2010.
8. Barzdins, J.; Cerans, K.; Liepins, R.; Sprogis, A.: UML Style Graphical Notation and Editor
   for OWL 2. In Proc. of BIR’2010, LNBIP, Springer 2010, vol. 64, p. 102-113, 2010.
9. Unified Modeling Language: Infrastructure, version 2.1. OMG Specification ptc/06-04-03,
   http://www.omg.org/docs/ptc/06-04-03.pdf
10.OWL 2 Manchester Syntax, http://www.w3.org/TR/owl2-manchester-syntax/
11.Klinov, P.; Vescovo, C.; Schneider, T.: Incrementally Updateable and Persistent
   Decomposition of OWL Ontologies. In Proc of OWLED 2012.



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