ODEWiki: A Semantic Wiki that Interoperates with the
ODESeW Semantic Portal
Adrián Siles, Angel López-Cima, Oscar Corcho and Asunción Gómez-Pérez

Facultad de Informática, Universidad Politécnica de Madrid,
Campus de Montegancedo, sn. 28660 Boadilla del Monte (Madrid, Spain)
asiles@delicias.dia.fi.upm.es, {alopez,ocorcho,asun}@fi.upm.es
Abstract. We present ODEWiki, a technology for the development of Semantic
Wikis, which has a combined set of added-value features over other existing
semantic wikis in the state of the art. Namely, ODEWiki interoperates with an
existing semantic portal technology (ODESeW), it manages inconsistencies
raised because of the distributed nature of knowledge base development and
maintenance, it uses RDFa for the annotation of the resulting wiki pages, it
follows a WYSIWYG approach, and it allows decoupling wiki pages and
ontology instances, that is, a wiki page may contain one or several ontology
instances. Although some of these features appear in some of the state-of-the-
art semantic wikis, but they are not combined together in a single solution.
Keywords: Semantic Wiki, ODEWiki
1 Introduction and Background
A wiki is software that allows users to create, edit, and link web pages easily1.
Wikis are often used to create collaborative websites and to power community
websites. As it happens with other Web sites, wikis are mainly focused on the
provision of content for human users, and lack from a clear semantic description of
their content. Semantic wikis have appeared in the last years as a technology that
builds on top of existing wikis, providing the same functionalities as these plus the
possibility of adding semantic annotations (normally in the form of RDF triples) to
the wiki pages that are generated.
In the last years, there has been a huge growth in the number of semantic wikis that
have been developed and made available to the community. For instance, the
OntoWorld site provides a non-exhaustive list of approximately 30 semantic wikis2.In
addition, there have been several workshops whose only topic has been about
semantic wikis. In our analysis, we have focused on some of the most popular ones:
Makna [1], Rhizome [2], Semantic Mediawiki [3], SweetWiki [4] and IkeWiki [5].
Some of the common characteristics of all these technologies are related to the
following aspects:

1 http://en.wikipedia.org/wiki/Wiki
2 http://ontoworld.org/wiki/Semantic_Wiki_State_Of_The_Art

- Annotation. This is the mechanism by which semantic annotations are related to
the information provided in a wiki page (normally in a textual form). These
semantic annotations may be related to existing ontologies or only be plain RDF,
which is used mainly as a syntax for providing additional information.
- Edition. This is the mechanism by which users can add semantic information not
only to the wiki pages that they are editing (this is the annotation process
aforementioned), but also the knowledge base that acts as a knowledge repository
for those wiki pages.
- Semantic search. This is the mechanism by which users may look for wiki pages
taking into account their semantic annotations.
- Visualization. This is the mechanism by which semantic wikis visualize the
semantic information about ontologies and their corresponding instances in the
knowledge base.
- Navigation. This is the mechanism by which users can navigate between wiki
pages taking into account the semantic relationships that are established by the
annotations associated to them.

Although these are common features for semantic wikis, not all the existing
semantic wiki technologies offer all these services, and there are many differences
among different technologies with respect to the degree of complexity and
functionality in each of these categories.
After an analysis of the state of the art in semantic wiki technologies, we have
discovered several limitations of all of them:
- None of the existing semantic wikis is used together with a knowledge portal.
This means that, although these applications are similar (semantic wikis and
knowledge portals allow creating and maintaining knowledge bases), their
strengths are not combined in any single solution. This could facilitate processes
of collaborative knowledge update and different publishing options for
knowledge portals, and knowledge edition and curation workflows for semantic
wikis.
- Only one of the analyzed semantic wiki technologies (SweetWiki) makes use of
the latest developments in the use of XHTML tags to include RDF triples
(RDFa3). This fact is very important for automatic data discovery using same
wiki page, that is, persons and computers can be extract same information from
this page.
- Only one of the analyzed semantic wiki technologies (SweetWiki) follows a
WYSIWYG (What You See Is What You Get) approach, which facilitates the
annotation of wiki pages for non-experts. The rest of technologies require users
to learn a new set of tags or syntax to include these annotations, and also require
users to know the ontologies to be used in advance, or to have them opened in a
different part of the web site.
- In most cases, each wiki page is associated to only one instance of an ontology.
This means that each page may only describe an individual, which makes it
difficult, for instance, to create and annotate more complex pages which contain
and declare several instances (e.g., a page that contains information about a set of

3 http://www.w3.org/TR/xhtml-rdfa-primer/

persons that belong to an institution, where we want to have more information
about them than simply their name).

Taking into account the aforementioned limitations, we have designed and
implemented ODEWiki, which is a semantic wiki that is integrated with the ODESeW
semantic portal [6] [7] [8]. This semantic wiki provides the most common
functionalities that are provided by most of the existing semantic wikis: annotation,
edition, search, navigation and visualization. And besides being integrated with a
semantic portal, which acts as a knowledge repository for the wiki plus as an
alternative knowledge publishing system. ODEWiki combines features that are only
found in some of the state-of-the-art semantic wikis, such as the use of RDFa for the
annotation of the resulting wiki pages, a WYSIWYG approach, and the decoupling of
wiki pages and ontology instances, that is, a wiki page may contain one or several
ontology instances.
In this demo, we will demonstrate how to edit semantically enabled wiki pages
with this technology, together with the advantages of the integration with a semantic
portal, so that the visitor will know how to operate with this technology.
2 Annotation and edition in ODEWiki
Most of the limitations identified in the state of art are related to characteristics of
the annotation and edition functionalities offered by wikis. In annotation and edition,
users can use a WYSIWYG user interface to annotate wiki pages with semantic data,
which is included in the wiki page using the RDFa format. This wiki page, and the
semantic data included into it, is not modified until the user decides to modify it. This
fact sometimes causes the semantic data to have external inconsistencies with the
underlying knowledge base, and therefore with the ODESeW semantic portal or other
wiki pages. ODEWiki provides a mechanism to automatically detect and manually
correct these external inconsistencies. We understand by external inconsistencies
those that are related to the following situations:
- The wiki page contains an instance that is not present in the knowledge base
(e.g., “onto:AdriánSiles rdf:type onto:Person”). This may have happened because
another wiki page or an external system has deleted that instance from the
knowledge base.
- The wiki page contains annotations of an instance that exists in the knowledge
base. However, the annotation itself (in other words, the RDF triple) does not
exist in the knowledge base4 (e.g. “onto:AdriánSiles onto:belongsTo onto:UPM”,
where onto:belongsTo has been removed from the ontology, onto:UPM has

4 Taking into account the Open World Assumption (OWA), this situation should not be
considered as a problem, since we can always have annotations about an ontology instance
that has not been defined elsewhere, but since this system is connected to a knowledge portal
where we consider the Closed World Assumption (CWA), we must assume here this
behavior. This behavior, however, could be changed accordingly in case that the OWA.

disappeared, this person has stopped belonging to onto:UPM, etc.). To some
extent, this may be seen as a generalization of the previous case.
These external inconsistencies are checked whenever a wiki page is going to be
visualized or when the user is going to start editing it. The user is notified of the
inconsistencies that have been found (as shown in figure 1) and can take any of the
following decisions: delete the corresponding RDF triple from the wiki page or from
the knowledge base, or include the RDF triple into the knowledge base.


Figure 1. Notification of inconsistencies in a wiki page.

Users can annotate wiki pages in two ways, using semantic data from the
knowledge base or adding new semantic data. Semantic data added to a wiki page is
automatically added into the knowledge base. Not only can users add semantic data
into the underlying knowledge base, but also can they delete, using a special action
attribute in RDFa triple, semantic data form the knowledge base and from the wiki
page. Users are responsible to take specific actions to avoid deleting relevant semantic
data. In fact, ODEWiki is not recommended to be used in open environments, that is,
ODEWiki is specifically designed to be used inside companies or organizations.
ODEWiki also provides a mechanism to automatically detect and manually correct
internal inconsistencies. We understand by internal inconsistencies those that are
related to the following situation:
- A wiki page contains annotations of an instance that is, at the same time,
removed from that page (“onto:AdriánSiles onto:belongsTo onto:UPM” is added
to the knowledge base from the wiki page, but at the same time the wiki page
contains an action to remove the triple “onto:AdriánSiles rdf:type onto:Person”
and there is no other “onto:AdriánSiles rdf:type X” or “onto:AdriánSiles rdf:label
X” triple in the knowledge base, which causes the removal of that instance).
3 Conclusions and future work
In this paper, we have shown some of the limitations of the most relevant semantic
wiki technologies, which are mainly, related to their annotation and edition
functionalities, especially in what respects to collaborative and distributed edition of
semantic information. To overcome these limitations, we have built ODEWiki, a
semantic wiki that is interconnected with a knowledge portal, which acts both as a
knowledge repository and as an alternative publication and knowledge edition
platform.
As part of our future work in this technology, we will focus on the provision of an
improved search functionality that goes beyond the current state of the art in semantic

search in existing semantic wikis (which is based on the SPARQL protocol). And in
an improved navigation model that inherits some of the characteristics of the
navigation model of ODESeW [8].
Acknowledgement
This work has been funded by the UPM-funded project “Extensiones a portales
semánticos con wikis semántico”5 (CCG06-UPM/INF-284).
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5 Extensions to semantic portals with semantic wikis.