Collaborative ontology engineering: a survey <s> Integrated development environments <s> Reusable ontologies are becoming increasingly important for tasks such as information integration, knowledge-level interoperation and knowledge-base development. We have developed a set of tools and services to support the process of achieving consensus on commonly shared ontologies by geographically distributed groups. These tools make use of the World Wide Web to enable wide access and provide users with the ability to publish, browse, create and edit ontologies stored on anontology server. Users can quickly assemble a new ontology from a library of modules. We discuss how our system was constructed, how it exploits existing protocols and browsing tools, and our experience supporting hundreds of users. We describe applications using our tools to achieve consensus on ontologies and to integrate information.The Ontolingua Server may be accessed through the URLhttp://ontolingua.stanford.edu <s> BIB001 </s> Collaborative ontology engineering: a survey <s> Integrated development environments <s> In traditional software systems, significant attention is devoted to keeping modules well separated and coherent with respect to functionality, thus ensuring that changes in the system are localized to a handful of modules. Reuse is seen as the key method in reaching that goal. Ontology-based systems on the Semantic Web are just a special class of software systems, so the same principles apply. In this article, we present an integrated framework for managing multiple and distributed ontologies on the Semant ic Web. It is based on the representation model for ontologies, trading off between expressivity and tractability. In our framework, we provide features for reusing existing ontologies and for evolving them while retaining the consistency. The approach is implemented within KAON, the Karlsruhe Ontology and Semantic Web tool suite. <s> BIB002
Features for allowing multiple users to simultaneously access and edit the same ontology have been part of ontology engineering environments since their very beginning. Ontolingua, for instance, was one of the first to provide group access control and multi-user sessions BIB001 . Users are notified of the changes in the ontologies made by the other users via hyperlinks that describe such changes in terms of basic operations-add, delete and modify. WebOnto supports asynchronous and synchronous discussions on ontologies through the Tadzebao system  . As part of such discussions, a user issues an argument or comments on a particular argument through the placement of a poster visible to all other users. In OntoEdit, emphasis is put on facilitating interaction among users during the requirements analysis phase of the engineering process  . With the OntoKick plug-in, the engineering team collaboratively specifies the domain and goal of the ontology, design guidelines, relevant resources and the means to extract structured knowledge out of these resources. A second OntoEdit plug-in, Mind2Onto, focuses on integration of the extracted structures towards an initial ontology. Collaboration is supported in the form of brainstorming sessions whose results are recorded with the help of the plug-in. It integrates the mind map tool for graphical representations of hierarchical structures. Moreover, it allows users to simultaneously refine the initial version of the ontology into a formal ontology based on the specified requirements. To do so, the system employs a locking and transaction protocol to ensure the model consistency and concurrency. Such features are also covered by the KAON ontology management framework BIB002 , which, among other things, defines a set of interfaces for accessing distributed ontologies, and for consistency checking, change tracking or concurrency conflict detection.  With ontology-based technology, gaining more and more popularity outside research labs industry-strength ontology engineering environments providing fully fledged collaboration support have become available. The NeOn Toolkit and Collaborative Prote´ge´are two of the most prominent freely available examples. The NeOn Toolkit is developed as a set of Eclipse plug-ins for engineering interconnected ontologies 22 . It offers standard features for ontology development, including ontology editing, browsing and import/export (F-logic, OWL), as well as more advanced plug-ins for visual modeling (OntoModel), ontology reuse (Watson, Oyster), ontology learning (Text2Onto), ontology alignment (R2O, FOAM) and collaboration (WikiFactory, Cicero). WikiFactory enables the automatic creation of semantic wiki-based Web sites, their dynamical management at run time, and the synchronization between wiki content and OWL ontologies. In this way, specific aspects of an ontology engineering process, most notably those that take most benefit from an interactive environment, can be carried out in a wiki, and their results transferred into an ontology. Complementary, Cicero allows asynchronous discussions on ontology-engineering-related issues, and supports decision making. It is based on a simplified version of DILIGENT (as discussed in Section 3.3). Collaborative Prote´ge´is an alternative version of the existing base Prote´ge´system, and probably the most comprehensive tool for collaborative ontology engineering currently available 23 . It implements features for discussion and conflict resolution in order to facilitate interaction between the participants. The system allows multiple users to edit the same ontology in multi-user or standalone mode. In addition to common editing operations, the system enables annotation with pre-defined annotation types for both ontological primitives (i.e. classes, properties, individuals) and ontology changes (i.e. class creation/deletion/renaming). In this way, it allows the user to document the ontology engineering process, in particular the rationale for taking specific decisions, in a systematic way. Collaborative Prote´ge´furthermore offers search and filter functionalities for accessing such user annotations. It also provides discussion threads for users to reply to comments and a chat channel for direct communication. Decisions follow two types of voting mechanisms, a five-star and agree/disagree type of voting, implemented and represented as annotation types in the system.