The fast growth and spread of Web 2.0 environments have demonstrated the great willingness of general Web users to contribute and share various type of content and information. Many very successful web sites currently exist which thrive on the wisdom of the crowd, where web users in general are the sole data providers and curators. The Semantic Web calls for knowledge to be semantically represented using ontologies to allow for better access and sharing of data. However, constructing ontologies collaboratively is not well supported by most existing ontology and knowledge-base editing tools. This has resulted in the recent emergence of a new range of collaborative ontology construction tools with the aim of integrating some Web 2.0 features into the process of structured knowledge construction. This paper provides a survey of the start of the art of these tools, and highlights their significant features and capabilities

Alani, Harith

Correndo, Gianluca

English

Southampton (e-Prints Soton)

Survey of tools for collaborative knowledge construction and sharingGianluca Correndo, Harith AlaniSchool of Electronics and Computer ScienceUniversity of SouthamptonSO17 1BJ, Southampton, United Kingdomgc3@ecs.soton.ac.uk, ha@ecs.soton.ac.ukAbstractThe 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. IntroductionThe 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 costlyreworks. 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. Goodandcolleagues(see[5])showedhowSWuserscansuccessfullycollaboratetonegotiateandbuildgood 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 ConstructionSince 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.2.1. Related WorkThe 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. BibSonomyBibSonomy [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 toprovide 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. DBinDBin [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. HozoHozo [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 presentin 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. OntoWikiOntoWiki [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:• Changetracking: KBchangesaretrackedandtheuserscan 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 task2.6. Collaborative Prot´ eg´ eCollaborative Prot´ eg´ e [9] is a prototypical extension ofthe Prot´ eg´ e ontology editor from Stanford Medical Infor-matics department for addressing social editing of ontolo-gies. The tool adopts a frame-like representation paradigmfor 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, Prot´ eg´ e has providedsome features for addressing the discussion between usersand conﬂict resolution by means of annotations that de-scribes changes, proposals, votes, advice, comments etc.Usingsuchadditionalannotationconcepts, theusercanpro-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 activetopicsandinstantmessagingforconnectinguserswithsameinterests on the model.2.7. SOBOLEOSOBOLEO [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. ComparisonTable 1 compares the main features provided by the toolssurveyedabovewith respect tomodeleditingand thedegreeof 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.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-turesTool Formality Properties Instances TagsBibSonomy Uncontrolled Vo-cabularyXDBin Formal Ontology X X XHozo Formal Ontology X XOntoWiki Formal Ontology X XCollab.Prot´ eg´ eFormal Ontology X XSOBOLEO Taxonomy XTable 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-turesTool Supervision Argumentation Social toolsBibSonomy XDBinHozoOntoWiki XCollab.Prot´ eg´ eX X XSOBOLEO X4. ConclusionsThis 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 fortagging, 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. AcknowledgmentThis 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.References[1] S.Auer, S.Dietzold, J.Lehmann, andT.Riechert. Ontowiki:A tool for social, semantic collaboration. In Workshop onSocial and Collaborative Construction of Structured Knowl-edge (CKC 2007) at WWW 2007, Banff, Canada, 2007.[2] T. Berners-Lee, J. Hendler, and O. Lassila. The semanticweb. Scientiﬁc American, May 2001.[3] J. Euzenat. Building consensual knowledge bases: Contextand architecture. In N. Mars, editor, Towards Very LargeKnowledge Bases - Proceedings of the KB&KS ’95 Confer-ence, pages 143–155, 1995.[4] A. Farquhar, R. Fikes, and J. Rice. The ontolingua server: Atool for collaborative ontology construction, 1996.[5] B. M. Good, E. M. Tranﬁeld, P. C. Tan, M. Shehata, G. K.Singhera, J. Gosselink, E. B. Okon, and M. D. Wilkinson.Fast, cheap and out of control: A zero curation model forontology development. In Paciﬁc Symposium on Biocom-puting, pages 128–139, 2006.[6] A. Hotho, R. J¨ aschke, C. Schmitz, and G. Stumme. BibSon-omy: A social bookmark and publication sharing system.In Proceedings of the Conceptual Structures Tool Interop-erability Workshop at the 14th International Conference onConceptual Structures, 2006.[7] K. Kozaki, E. Sunagawa, Y. Kitamura, and R. Mizoguchi.Distributed and collaborative construction of ontologies us-ing hozo. In Workshop on Social and Collaborative Con-struction of Structured Knowledge (CKC 2007) at WWW2007, Banff, Canada, 2007.[8] N. Shadbolt, T. Berners-Lee, and W. Hall. The semantic webrevisited. Intelligent Systems, IEEE [see also IEEE Intelli-gent Systems and Their Applications], 21(3):96–101, 2006.[9] T. Tudorache and N. Noy. Collaborative Prot´ eg´ e. InWorkshop on Social and Collaborative Construction ofStructured Knowledge (CKC 2007) at WWW 2007, Banff,Canada, 2007.[10] G. Tummarello and C. Morbidoni. Collaboratively buildingstructured knowledge with dbin: from del.icio.us tags to an’rdfs folksonomy’. In Workshop on Social and Collabora-tive Construction of Structured Knowledge (CKC 2007) atWWW 2007, Banff, Canada, 2007.[11] V. Zacharias and S. Braun. Soboleo – social bookmarkingand lightweight engineering of ontologies. In Proc. WWW2007 Workshop on Social and Collaborative Construction ofStructured Knowledge, Banff, Canada, May 2007.

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Survey of tools for collaborative knowledge construction and sharing

Crossref

Survey of Tools for Collaborative Knowledge Construction and Sharing

Gianluca Correndo

Harith Alani

The fast growth and spread of Web 2.0 environments have demonstrated the great willingness of general Web users to contribute and share various type of content and information.  Many very successful web sites currently exist which thrive on the wisdom of the crowd, where web users in general are the sole data providers and curators. The Semantic Web  calls for knowledge to be semantically represented using ontologies to allow for better access and sharing of data. However, constructing ontologies collaboratively is not well supported by most existing ontology and knowledge-base editing tools. This has resulted in the recent emergence of a new range of collaborative ontology construction tools with the aim of integrating some Web 2.0 features into the process of structured knowledge construction. This paper provides a survey of the start of the art of these tools, and highlights their significant features and capabilities

Open Research Online

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsSurvey of tools for collaborative knowledgeconstruction and sharingConference or Workshop ItemHow to cite:Correndo, Gianluca and Alani, Harith (2007). Survey of tools for collaborative knowledge construction andsharing. In: Workshop on Collective Intelligence on Semantic Web (CISW 2007), 2-5 Nov 2007, Fremont, CA, USA.For guidance on citations see FAQs.c© 2007 The AuthorsVersion: Accepted ManuscriptLink(s) to article on publisher’s website:http://dx.doi.org/doi:10.1109/WI-IATW.2007.35Copyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.ukSurvey of tools for collaborative knowledge construction and sharingGianluca Correndo, Harith AlaniSchool of Electronics and Computer ScienceUniversity of SouthamptonSO17 1BJ, Southampton, United Kingdomgc3@ecs.soton.ac.uk, ha@ecs.soton.ac.ukAbstractThe 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. IntroductionThe 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 costlyreworks. 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 ConstructionSince 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.2.1. Related WorkThe 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. BibSonomyBibSonomy [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 toprovide 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. DBinDBin [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. HozoHozo [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 presentin 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. OntoWikiOntoWiki [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 task2.6. Collaborative Prote´ge´Collaborative Prote´ge´ [9] is a prototypical extension ofthe Prote´ge´ ontology editor from Stanford Medical Infor-matics department for addressing social editing of ontolo-gies. The tool adopts a frame-like representation paradigmfor 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, Prote´ge´ 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. SOBOLEOSOBOLEO [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. ComparisonTable 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.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-turesTool Formality Properties Instances TagsBibSonomy Uncontrolled Vo-cabularyXDBin Formal Ontology X X XHozo Formal Ontology X XOntoWiki Formal Ontology X XCollab.Prote´ge´Formal Ontology X XSOBOLEO Taxonomy XTable 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-turesTool Supervision Argumentation Social toolsBibSonomy XDBinHozoOntoWiki XCollab.Prote´ge´X X XSOBOLEO X4. ConclusionsThis 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 fortagging, 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. AcknowledgmentThis 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.References[1] S. Auer, S. Dietzold, J. Lehmann, and T. Riechert. Ontowiki:A tool for social, semantic collaboration. In Workshop onSocial and Collaborative Construction of Structured Knowl-edge (CKC 2007) at WWW 2007, Banff, Canada, 2007.[2] T. Berners-Lee, J. Hendler, and O. Lassila. The semanticweb. Scientific American, May 2001.[3] J. Euzenat. Building consensual knowledge bases: Contextand architecture. In N. Mars, editor, Towards Very LargeKnowledge Bases - Proceedings of the KB&KS ’95 Confer-ence, pages 143–155, 1995.[4] A. Farquhar, R. Fikes, and J. Rice. The ontolingua server: Atool for collaborative ontology construction, 1996.[5] B. M. Good, E. M. Tranfield, P. C. Tan, M. Shehata, G. K.Singhera, J. Gosselink, E. B. Okon, and M. D. Wilkinson.Fast, cheap and out of control: A zero curation model forontology development. In Pacific Symposium on Biocom-puting, pages 128–139, 2006.[6] A. Hotho, R. Ja¨schke, C. Schmitz, and G. Stumme. BibSon-omy: A social bookmark and publication sharing system.In Proceedings of the Conceptual Structures Tool Interop-erability Workshop at the 14th International Conference onConceptual Structures, 2006.[7] K. Kozaki, E. Sunagawa, Y. Kitamura, and R. Mizoguchi.Distributed and collaborative construction of ontologies us-ing hozo. In Workshop on Social and Collaborative Con-struction of Structured Knowledge (CKC 2007) at WWW2007, Banff, Canada, 2007.[8] N. Shadbolt, T. Berners-Lee, andW. Hall. The semantic webrevisited. Intelligent Systems, IEEE [see also IEEE Intelli-gent Systems and Their Applications], 21(3):96–101, 2006.[9] T. Tudorache and N. Noy. Collaborative Prote´ge´. InWorkshop on Social and Collaborative Construction ofStructured Knowledge (CKC 2007) at WWW 2007, Banff,Canada, 2007.[10] G. Tummarello and C. Morbidoni. Collaboratively buildingstructured knowledge with dbin: from del.icio.us tags to an’rdfs folksonomy’. In Workshop on Social and Collabora-tive Construction of Structured Knowledge (CKC 2007) atWWW 2007, Banff, Canada, 2007.[11] V. Zacharias and S. Braun. Soboleo – social bookmarkingand lightweight engineering of ontologies. In Proc. WWW2007 Workshop on Social and Collaborative Construction ofStructured Knowledge, Banff, Canada, May 2007.

Survey of tools for collaborative knowledge construction and sharing
Gianluca Correndo, Harith Alani
School of Electronics and Computer Science
University of Southampton
SO17 1BJ, Southampton, United Kingdom
gc3@ecs.soton.ac.uk, ha@ecs.soton.ac.uk
Abstract
The fast growth and spread of Web 2.0 environments
have demonstrated the great willingness of general Web
users to contribute and share various type of content and
information. Many very successful web sites currently ex-
ist which thrive on the wisdom of the crowd, where web
users in general are the sole data providers and curators.
The Semantic Web calls for knowledge to be semantically
represented using ontologies to allow for better access and
sharing of data. However, constructing ontologies collabo-
ratively is not well supported by most existing ontology and
knowledge-base editing tools. This has resulted in the re-
cent emergence of a new range of collaborative ontology
construction tools with the aim of integrating some Web 2.0
features into the process of structured knowledge construc-
tion. This paper provides a survey of the start of the art
of these tools, and highlights their significant features and
capabilities.
1. Introduction
The transformation of the web from a mere collection of
documents to a queryable knowledge-base (KB) is one of
the most prominent targets of Semantic Web (SW, [2]).
To help reach this goal, knowledge repositories need to
publish 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 focused
on building tools and capabilities for ontology and KB con-
struction. However, most of such tools have been designed
to be used by individuals or small teams that are geograph-
ically co-located. Support for distributed teams to remotely
and continuously collaborate on building ontologies and
knowledge repositories has been somewhat lacking in the
SW domain.
Defining an ontology for representing data semantics is
usually 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 of
a specific community and support their knowledge needs,
then it might be sensible to give this community the power
to maintain this ontology [8].
Some ontologies need to be agreed upon by the user
community, and reaching this agreement must be supported
by tools and methodologies to allow users to express their
views 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 demonstrated
how general web users can actively contribute and share
all 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 and
suggestions, etc. Good and colleagues (see [5]) showed how
SW users can successfully collaborate to negotiate and build
good quality ontologies when provided with a tool that sup-
ports such activities. In the following we will describe the
main features and capabilities of a number of tools that of-
fer various levels of collaboration with the goal of creating
structured knowledge.
2. Collaborative Knowledge Construction
Since the early nineties collaboration has been seen
as a key argument for constructing consensual knowledge
around 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 past
few years which support various kinds and levels of se-
mantic knowledge creation. This knowledge may vary
from simple bookmarking information, to instance data, to
complex OWL ontologies. In this paper we first have a
look at some of the early developments in the field and
then survey the tools presented at the workshop on Social
and Collaborative Construction of Structured Knowledge
(http://www2007.org/workshop-W7.php) at the 16th Inter-
national World Wide Web conference.
2.1. Related Work
The distributed editing and maintenance of formal arti-
facts, like knowledge bases or ontologies, have posed some
challenges 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 how
to enhance understanding. The first approaches applied a
divide et impera philosophy by dividing domains of interest
into modules with well established dependencies.
Ontolingua [4] was one of the first tools for authoring
formal ontologies with a collaborative flavour. The tool
manages shared sessions where users can collaboratively
edit a set of ontologies. Ontoligua supports user groups and
different access rights, similar to a traditional distributed
filesystem. All users participating in an ontology building
session in Ontolingua are notified of any changes inserted
by other users. Users can reuse and share ontology mod-
ules, thus creating a collaborative environment. The former
language used in Ontolingua is KIF, a very expressive logic,
and the tool provided a consistency checking service.
Ontolingua provided valid solutions for achieving two
of the four goals stated above, orchestration and global
consistency, but, since different subdomains were treated
in different modules, it did not address in depth how to
express different conceptualisations and modelling issues.
Some later approaches tried to augment models with argu-
mentation about the validity of proposals or discussing on
their faults. One tool that integrated argumentations in pro-
posals is Co4 [3] which aimed to increase consensus and
cooperation 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 be
shared, 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 maintain
a 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 improving
the proposal.
2.2. BibSonomy
BibSonomy [6] is a social tagging system developed by
the University of Kassel and the L3S research institute of
Hannover. BibSonomy helps in organising and sharing re-
sources such as bookmarks and publications, integrating
capabilities separately provided by previous social tagging
systems. 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 add
an 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 that
are more general than the ones used for a resource are im-
plicitly added to the set of tags and used when searching
for information if required. Using these relations, the user
is not forced to apply all the possible tags to resources but
only the most specific ones.
The interaction provided by BibSonomy is similar to
common social bookmarking systems. A user submitting
a resource (eg reference, web page) to BibSonomy will be
recommended a number of tags that were given to the same
resource by others, which the user may choose to reuse, or
add new ones. Bookmarked resources can be made private
or shared among the whole community. When shared, the
bookmark 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 the
group.
2.3. DBin
DBin [10] is an application that allows a group of users
to share structured content using RDF as a content language
and a P2P network as a content provisioning infrastructure.
The tool supports the most well known query languages for
RDF (i.e. RDQL, RQL and SeRQL) and decorates each
information 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 of
reusable widgets that handle RDF data (e.g. for vi-
sualising maps or URLs).
• Provenance certificates: every content provided by a
user to the community using DBin is certified by a sig-
nature that uniquely identifies the user.
• RDFGrowth: a P2P algorithm that allows users and
communities to specifically define the items that are of
interest 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 ontologies
in a distributed environment. The main focus of the tool is
to provide consistency among inter-dependent ontologies in
a scenario where they are asynchronously developed by dif-
ferent users. In order to provide such global consistency, the
tool provides basically two capabilities: dependency man-
agement and consistency harmonization.
Like many version control systems, Hozo allows to lock
and unlock modules, that in this case are ontologies present
in the system, in order to prevent any modifications from
other users. The state of the source ontologies is broad-
casted to all users along with their update status in order
to let users know, which ontologies are in rework and what
modifications 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 user
can 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 aim
of OntoWiki is to provide an intuitive and collaborative tool
for the editing of RDF content that supports knowledge en-
gineering in a distributed (web based) environment. The
user can browse the taxonomy tree of the concepts. Once a
concept is selected, the user can see its instances. Once an
instance is selected, the user can then choose a visualisation
for it or edit the RDF structure to add additional properties
or values to the instance. OntoWiki provides a text search
facility on literal values, supported by other search filtering
options on frequency, instance groups, facets, etc.
OntoWiki also provides a number of features for enhanc-
ing social interaction when developing KBs. The features
implemented follow the Wiki paradigm where the system is
seen as a common space open to contributions where users
can 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 features
can be summarised as follows:
• Change tracking: KB changes are tracked and the users
can subscribe to RSS feeds for being informed
• Commenting: all the changes can be commented on,
annotated and rated by users in order to discuss and
agree on their usefulness
• Popularity: all accesses to the KB are logged and in-
stances can be rated (e.g. for originality, quality and
presentation) by users in order to measure instance
popularity
• Provenance: the system tracks contributions from
users to highlight whose contributions are added to the
common task
2.6. Collaborative Protégé
Collaborative Protégé [9] is a prototypical extension of
the Protégé 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 a
server 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 to
the ontologies. In this prototypical extension, the users can
make changes on a shared model and see in real time the
changes made by other users.
For empowering a community to build an agreed com-
plex artifact, such as an ontology, Protégé has provided
some features for addressing the discussion between users
and 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 capability
for annotating in order to clearly identify the more active
topics and instant messaging for connecting users with same
interests on the model.
2.7. SOBOLEO
SOBOLEO [11] is a web based collaborative tool for the
engineering 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 for
bridging 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) and
such changes are not supervised by a central authority. The
editor allows users to send instant messages to users that are
currently editing the taxonomy. Using concepts from the
mantained 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 managed
ontology 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 tools
surveyed above with respect to model editing and the degree
of formality of the model itself. It is important to know if
the semantics of the model have a strong formal basis or not
as this will influence the use of the tool for a particular task.
Moreover, the table denotes, for each tool, the possibility
to define relations between concepts other than the classic
isa and indicates whether it is possible to create instances
from the used ontologies. Finally, the last column shows
whether the tools allows using concepts for tagging external
resources like bookmarks, pictures etc.
Table 1. Comparison of model editing fea-
tures
Tool Formality Properties Instances Tags
BibSonomy Uncontrolled Vo-
cabulary
X
DBin Formal Ontology X X X
Hozo Formal Ontology X X
OntoWiki Formal Ontology X X
Collab.
Protégé
Formal Ontology X X
SOBOLEO Taxonomy X
Table 2 compares the features provided by the tools
for driving discussions and negotiations about the model
among the community. The first feature taken into account
is the possibility to supervise the changes on the model hav-
ing an effective control over its evolution. An entry in the
second column indicates that the tool provides the ability to
add argumentation to the evolution of the model in order to
reach consensus or to discuss issues. The last feature taken
into account for comparing the tools is whether the users
can be connected by means of social tools with other users
of the community in support of the task (e.g. chat, instant
messaging, RSS).
Table 2. Comparison of model evolution fea-
tures
Tool Supervision Argumentation Social tools
BibSonomy X
DBin
Hozo
OntoWiki X
Collab.
Protégé
X X X
SOBOLEO X
4. Conclusions
This paper presented a brief survey of tools submitted to
the workshop for Social and Collaborative Construction of
Structured Knowledge which aimed at testing the state of
the art of such tools for collaborative knowledge construc-
tion to find out what users expect from such tools, and how
they should evolve in the future. The tools surveyed in this
paper support various tasks, such as tag-based taxonomy
building, KB creation, and ontology modelling. They also
vary greatly in terms of the functionalities they provide for
tagging, voting, discussion support, change control, visual-
isation, etc. This paper highlighted and compared the main
features of these tools to help reach a better understanding
of 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 part
of the Data and Information Fusion Defence Technology
Centre initiative.
References
[1] S. Auer, S. Dietzold, J. Lehmann, and T. Riechert. Ontowiki:
A tool for social, semantic collaboration. In Workshop on
Social and Collaborative Construction of Structured Knowl-
edge (CKC 2007) at WWW 2007, Banff, Canada, 2007.
[2] T. Berners-Lee, J. Hendler, and O. Lassila. The semantic
web. Scientific American, May 2001.
[3] J. Euzenat. Building consensual knowledge bases: Context
and architecture. In N. Mars, editor, Towards Very Large
Knowledge Bases - Proceedings of the KB&KS ’95 Confer-
ence, pages 143–155, 1995.
[4] A. Farquhar, R. Fikes, and J. Rice. The ontolingua server: A
tool for collaborative ontology construction, 1996.
[5] B. M. Good, E. M. Tranfield, P. C. Tan, M. Shehata, G. K.
Singhera, J. Gosselink, E. B. Okon, and M. D. Wilkinson.
Fast, cheap and out of control: A zero curation model for
ontology development. In Pacific Symposium on Biocom-
puting, pages 128–139, 2006.
[6] A. Hotho, R. Jäschke, C. Schmitz, and G. Stumme. BibSon-
omy: A social bookmark and publication sharing system.
In Proceedings of the Conceptual Structures Tool Interop-
erability Workshop at the 14th International Conference on
Conceptual Structures, 2006.
[7] K. Kozaki, E. Sunagawa, Y. Kitamura, and R. Mizoguchi.
Distributed and collaborative construction of ontologies us-
ing hozo. In Workshop on Social and Collaborative Con-
struction of Structured Knowledge (CKC 2007) at WWW
2007, Banff, Canada, 2007.
[8] N. Shadbolt, T. Berners-Lee, and W. Hall. The semantic web
revisited. Intelligent Systems, IEEE [see also IEEE Intelli-
gent Systems and Their Applications], 21(3):96–101, 2006.
[9] T. Tudorache and N. Noy. Collaborative Protégé. In
Workshop on Social and Collaborative Construction of
Structured Knowledge (CKC 2007) at WWW 2007, Banff,
Canada, 2007.
[10] G. Tummarello and C. Morbidoni. Collaboratively building
structured knowledge with dbin: from del.icio.us tags to an
’rdfs folksonomy’. In Workshop on Social and Collabora-
tive Construction of Structured Knowledge (CKC 2007) at
WWW 2007, Banff, Canada, 2007.
[11] V. Zacharias and S. Braun. Soboleo – social bookmarking
and lightweight engineering of ontologies. In Proc. WWW
2007 Workshop on Social and Collaborative Construction of
Structured Knowledge, Banff, Canada, May 2007.


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