Survey of tools for collaborative knowledge construction and sharing

Gianluca Correndo, Harith AlaniSchool of Electronics and Computer Science

University of SouthamptonSO17 1BJ, Southampton, United Kingdomgc3@ecs.soton.ac.uk, ha@ecs.soton.ac.uk

Abstract

The fast growth and spread of Web 2.0 environmentshave demonstrated the great willingness of general Webusers to contribute and share various type of content andinformation. Many very successful web sites currently ex-ist which thrive on the wisdom of the crowd, where webusers in general are the sole data providers and curators.The Semantic Web calls for knowledge to be semanticallyrepresented using ontologies to allow for better access andsharing of data. However, constructing ontologies collabo-ratively is not well supported by most existing ontology andknowledge-base editing tools. This has resulted in the re-cent emergence of a new range of collaborative ontologyconstruction tools with the aim of integrating some Web 2.0features into the process of structured knowledge construc-tion. This paper provides a survey of the start of the artof these tools, and highlights their significant features andcapabilities.

1. Introduction

The transformation of the web from a mere collection ofdocuments to a queryable knowledge-base (KB) is one ofthe most prominent targets of Semantic Web (SW, [2]).

To help reach this goal, knowledge repositories need topublish semantic representations of their data models to en-able other machines to understand and query their content.To this end, much research and development has focusedon building tools and capabilities for ontology and KB con-struction. However, most of such tools have been designedto be used by individuals or small teams that are geograph-ically co-located. Support for distributed teams to remotelyand continuously collaborate on building ontologies andknowledge repositories has been somewhat lacking in theSW domain.

Defining an ontology for representing data semantics isusually a costly and time consuming task. Furthermore,knowledge evolves over time and this is reflected in costly

reworks. If an ontology is meant to represent the views ofa specific community and support their knowledge needs,then it might be sensible to give this community the powerto maintain this ontology [8].

Some ontologies need to be agreed upon by the usercommunity, and reaching this agreement must be supportedby tools and methodologies to allow users to express theirviews and opinions freely, using for example tags to anno-tate certain objects or highlight some issues.

The rise of social Web 2.0 applications has demonstratedhow general web users can actively contribute and shareall sorts of data and information, such as images, videos,bookmarks, opinions, diaries and experiences, etc. Map-ping this functionality to the SW means giving more sup-port to users to dynamically and collaboratively build on-tologies add semantics to data, discuss and share views andsuggestions, etc. Good and colleagues (see [5]) showed howSW users can successfully collaborate to negotiate and buildgood quality ontologies when provided with a tool that sup-ports such activities. In the following we will describe themain features and capabilities of a number of tools that of-fer various levels of collaboration with the goal of creatingstructured knowledge.

2. Collaborative Knowledge Construction

Since the early nineties collaboration has been seenas a key argument for constructing consensual knowledgearound a domain and a great effort has been spent in dis-covering enabling technologies for facilitating such con-sensus reaching. Several tools have emerged in the pastfew years which support various kinds and levels of se-mantic knowledge creation. This knowledge may varyfrom simple bookmarking information, to instance data, tocomplex OWL ontologies. In this paper we first have alook at some of the early developments in the field andthen survey the tools presented at the workshop on Socialand Collaborative Construction of Structured Knowledge(http://www2007.org/workshop-W7.php) at the 16th Inter-national World Wide Web conference.

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2007 IEEE/WIC/ACM International Conferences on Web Intelligence and Intelligent Agent Technology - Workshops

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2007 IEEE/WIC/ACM International Conferences on Web Intelligence and Intelligent Agent Technology - Workshops

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2.1. Related Work

The distributed editing and maintenance of formal arti-facts, like knowledge bases or ontologies, have posed somechallenges to computer science with a number of issues:how to better orchestrate collaborative efforts, how to as-sure global consistency, how to reach consensus, and howto enhance understanding. The first approaches applied adivide et impera philosophy by dividing domains of interestinto modules with well established dependencies.

Ontolingua [4] was one of the first tools for authoringformal ontologies with a collaborative flavour. The toolmanages shared sessions where users can collaborativelyedit a set of ontologies. Ontoligua supports user groups anddifferent access rights, similar to a traditional distributedfilesystem. All users participating in an ontology buildingsession in Ontolingua are notified of any changes insertedby other users. Users can reuse and share ontology mod-ules, thus creating a collaborative environment. The formerlanguage used in Ontolingua is KIF, a very expressive logic,and the tool provided a consistency checking service.

Ontolingua provided valid solutions for achieving twoof the four goals stated above, orchestration and globalconsistency, but, since different subdomains were treatedin different modules, it did not address in depth how toexpress different conceptualisations and modelling issues.Some later approaches tried to augment models with argu-mentation about the validity of proposals or discussing ontheir faults. One tool that integrated argumentations in pro-posals is Co4 [3] which aimed to increase consensus andcooperation in KB creation by having a protocol for man-aging discussions.

In Co4, each user maintains a local KB that remains un-shared until the user decides that it is mature enough to beshared, totally or in part, with the community. The shar-ing activity is undertaken by means of change requests sub-mitted by users to the approval of the group who maintaina consensual KB. The submissions are managed with ax-ioms that the group can ”accept”, ”reject” or subject to ”re-vision”, in regard of providing suggestions for improvingthe proposal.

2.2. BibSonomy

BibSonomy [6] is a social tagging system developed bythe University of Kassel and the L3S research institute ofHannover. BibSonomy helps in organising and sharing re-sources such as bookmarks and publications, integratingcapabilities separately provided by previous social taggingsystems. The collection of tags is a weak notion of con-trolled vocabulary where ’control’ is performed by the com-munity itself. BibSonomy introduced the possibility to addan informal notion of isa relation between tags in order to

provide a notion of taxonomic structure that can be help-ful when retrieving information. The idea is that tags thatare more general than the ones used for a resource are im-plicitly added to the set of tags and used when searchingfor information if required. Using these relations, the useris not forced to apply all the possible tags to resources butonly the most specific ones.

The interaction provided by BibSonomy is similar tocommon social bookmarking systems. A user submittinga resource (eg reference, web page) to BibSonomy will berecommended a number of tags that were given to the sameresource by others, which the user may choose to reuse, oradd new ones. Bookmarked resources can be made privateor shared among the whole community. When shared, thebookmark and all associated tags can be searched by oth-ers and used by the system for future tag recommendations.Users can formulate groups where they can limit the shar-ing of tags and resources to just the other members of thegroup.

2.3. DBin

DBin [10] is an application that allows a group of usersto share structured content using RDF as a content languageand a P2P network as a content provisioning infrastructure.The tool supports the most well known query languages forRDF (i.e. RDQL, RQL and SeRQL) and decorates eachinformation provided to the group with trust related infor-mation. The main services that DBin provides can be sum-marised as follow:

• Application container: the tool provides a set ofreusable widgets that handle RDF data (e.g. for vi-sualising maps or URLs).

• Provenance certificates: every content provided by auser to the community using DBin is certified by a sig-nature that uniquely identifies the user.

• RDFGrowth: a P2P algorithm that allows users andcommunities to specifically define the items that are ofinterest in order to receive only the relevant updates.

2.4. Hozo

Hozo [7] is a server based tool developed by the univer-sity of Osaka for supporting the development of ontologiesin a distributed environment. The main focus of the tool isto provide consistency among inter-dependent ontologies ina scenario where they are asynchronously developed by dif-ferent users. In order to provide such global consistency, thetool provides basically two capabilities: dependency man-agement and consistency harmonization.

Like many version control systems, Hozo allows to lockand unlock modules, that in this case are ontologies present

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in the system, in order to prevent any modifications fromother users. The state of the source ontologies is broad-casted to all users along with their update status in orderto let users know, which ontologies are in rework and whatmodifications have affected the focused concepts. Modifi-cations applied to the ontology entities (concepts and slots)are of three kinds: added, modified and deleted, and the usercan accept or reject each modification.

2.5. OntoWiki

OntoWiki [1] is a web based tool for collaborative edit-ing of information maps that supports a number of visuali-sation widgets for different kind of instance data. The aimof OntoWiki is to provide an intuitive and collaborative toolfor the editing of RDF content that supports knowledge en-gineering in a distributed (web based) environment. Theuser can browse the taxonomy tree of the concepts. Once aconcept is selected, the user can see its instances. Once aninstance is selected, the user can then choose a visualisationfor it or edit the RDF structure to add additional propertiesor values to the instance. OntoWiki provides a text searchfacility on literal values, supported by other search filteringoptions on frequency, instance groups, facets, etc.

OntoWiki also provides a number of features for enhanc-ing social interaction when developing KBs. The featuresimplemented follow the Wiki paradigm where the system isseen as a common space open to contributions where userscan collaborate to build information and to correct mistakes.All these features are intended to lower the cost of creat-ing and exchanging structured metadata and to set up an ef-fective scenario of collaboration. OntoWiki’s main featurescan be summarised as follows:

• Change tracking: KB changes are tracked and the userscan subscribe to RSS feeds for being informed

• Commenting: all the changes can be commented on,annotated and rated by users in order to discuss andagree on their usefulness

• Popularity: all accesses to the KB are logged and in-stances can be rated (e.g. for originality, quality andpresentation) by users in order to measure instancepopularity

• Provenance: the system tracks contributions fromusers to highlight whose contributions are added to thecommon task

2.6. Collaborative Protege

Collaborative Protege [9] is a prototypical extension ofthe Protege ontology editor from Stanford Medical Infor-matics department for addressing social editing of ontolo-gies. The tool adopts a frame-like representation paradigm

for editing ontologies, but supports axioms and many for-malisms for formal ontology description (RDF(S), OWL,XMI, N3). The basic version of the tool already supports aserver based editing of the ontologies, based on Java RMI(Remote Method Invocation), where the concept of prede-fined users and groups is used to define access policies tothe ontologies. In this prototypical extension, the users canmake changes on a shared model and see in real time thechanges made by other users.

For empowering a community to build an agreed com-plex artifact, such as an ontology, Protege has providedsome features for addressing the discussion between usersand conflict resolution by means of annotations that de-scribes changes, proposals, votes, advice, comments etc.Using such additional annotation concepts, the user can pro-vide structured information focused on the desired evolu-tion of the ontology and discuss it with the rest of the com-munity. Moreover, the tool allows a basic rating capabilityfor annotating in order to clearly identify the more activetopics and instant messaging for connecting users with sameinterests on the model.

2.7. SOBOLEO

SOBOLEO [11] is a web based collaborative tool for theengineering of taxonomies developed by the Research Cen-ter for Information Technologies of the University of Karl-sruhe. The tool allows users to mantain a shared taxonomy,using SKOS concepts (http://www.w3.org/2004/02/skos/),and to use such concepts for tagging internet resources.This integration of functionalities has been devised forbridging the gap between the creation of shared vocabular-ies and their use in organising internet resources.

The tool has a taxonomy editor for changing the hierar-chical definition of the concepts (no slots or axioms) andsuch changes are not supervised by a central authority. Theeditor allows users to send instant messages to users that arecurrently editing the taxonomy. Using concepts from themantained taxonomy, the user can tag internet resources,and the tool will prompt him/her with concepts used by oth-ers on same resources. SOBOLEO provides resource re-trieval features as well. Using concept from the managedontology as keywords, the user can search tagged resources(refining the search using broader and narrower concepts)or browse the taxonomy to look for tagged documents.

3. Comparison

Table 1 compares the main features provided by the toolssurveyed above with respect to model editing and the degreeof formality of the model itself. It is important to know ifthe semantics of the model have a strong formal basis or notas this will influence the use of the tool for a particular task.

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Moreover, the table denotes, for each tool, the possibilityto define relations between concepts other than the classicisa and indicates whether it is possible to create instancesfrom the used ontologies. Finally, the last column showswhether the tools allows using concepts for tagging externalresources like bookmarks, pictures etc.

Table 1. Comparison of model editing fea-tures

Tool Formality Properties Instances TagsBibSonomy Uncontrolled Vo-

cabularyX

DBin Formal Ontology X X XHozo Formal Ontology X XOntoWiki Formal Ontology X XCollab.Protege

Formal Ontology X X

SOBOLEO Taxonomy X

Table 2 compares the features provided by the toolsfor driving discussions and negotiations about the modelamong the community. The first feature taken into accountis the possibility to supervise the changes on the model hav-ing an effective control over its evolution. An entry in thesecond column indicates that the tool provides the ability toadd argumentation to the evolution of the model in order toreach consensus or to discuss issues. The last feature takeninto account for comparing the tools is whether the userscan be connected by means of social tools with other usersof the community in support of the task (e.g. chat, instantmessaging, RSS).

Table 2. Comparison of model evolution fea-tures

Tool Supervision Argumentation Social toolsBibSonomy XDBinHozoOntoWiki XCollab.Protege

X X X

SOBOLEO X

4. Conclusions

This paper presented a brief survey of tools submitted tothe workshop for Social and Collaborative Construction ofStructured Knowledge which aimed at testing the state ofthe art of such tools for collaborative knowledge construc-tion to find out what users expect from such tools, and howthey should evolve in the future. The tools surveyed in thispaper support various tasks, such as tag-based taxonomybuilding, KB creation, and ontology modelling. They alsovary greatly in terms of the functionalities they provide for

tagging, voting, discussion support, change control, visual-isation, etc. This paper highlighted and compared the mainfeatures of these tools to help reach a better understandingof what is currently available.

5. Acknowledgment

This work was funded by a grant awarded to General Dy-namics UK Ltd and the University of Southampton as partof the Data and Information Fusion Defence TechnologyCentre initiative.

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