Towards semantically-interlinked online communities

In this article Breslin et al. presented different types of online communities and tools that were at that time used to build and support online communities. As I discovered and stated in previous posts, those communities are islands that are not interlinked. The authors als presented the SIOC ontology. The goal of SIOC (Semantically-Interlinked Online Communities) is to interconnect these online communities. Community sites can include many discussion primitives, such as bulletin boards, weblogs and mailing lists, which are grouped under the concept of forum.

Walls between social networks by Berners Lee

Walls between social networks by Berners Lee

The authors formulated the challenges for SIOC as follows:

The grand challenge is adoption by community sites, i.e. how can the users be enticed to make use of the SIOC ontology. By using concepts that can be easily understood by site administrators, and by providing properties that are automatically created by an end-user, the SIOC ontology can be adopted in a useful way. A second challenge is how best to use SIOC with existing ontologies. This can be partially solved by mappings and interfaces to commonly-used ontologies such as Dublin Core 2, FOAF 3 and RSS 1.0 4. Another challenge is how SIOC will scale. If there are more sites to query, then there are more potential relevant results, but also longer response times and higher loads on the participating community sites. We will keep the scaling challenge in mind when creating a future architecture for an interconnected system of community sites.

The logo for the SIOC project

Image via Wikipedia

In the first section they presented the SIOC ontology. The ontology consists of two major parts: first, it contains classes and properties that describe discussion forums and posts in online community sites. Second, it includes mappings that relate SIOC to existing vocabularies such as FOAF and RSS. They described the main classes, important properties and of course the mappings. About that last subsection it is worthy noting that one of the main functions of SIOC is to provide a means for exchanging community instance data. Since there are already a considerable number of classes and properties defined in RDF on the Web, they provide mappings in RDFS and OWL to allow the import and export of SIOC instance data in different vocabularies. Therefore, they can leverage the instance data that is already available. They showed how classes in FOAF, RSS, and various email vocabularies correspond to SIOC classes. Mappings of properties are described in a similar manner.

Breslin et al. elaborated on how the exchange, both importing and exporting data can be carried out. The core use of SIOC will be in the exchange of instance data between sites. Wrappers will allow to export instances of community site concepts such as forums or posts in RDF format. They can also allow us to import SIOC instances to other non-SIOC systems. Then they described how to handle legacy systems. A large number of systems preceding the current Web are still deployed and widely used on the Internet. In contrast to web-based systems, where it’s just needed to translate the data, there is need to employ protocol wrappers for legacy protocols to HTTP. Providing mappings from web-based systems is somewhat easier than mapping from legacy systems since protocol translation is not needed here. However, most existing wrappers don’t export their data in SIOC, and only provide a document-based export functionality rather than a query interface. The authors demonstrated this concept by the example of the export from a WordPress blog.

They continued the discussion with an explanation of how RDF Store can facilitate the exchanging of instances. The web-based wrappers just provide simple document-based export facilities. Replacing the simple wrappers with full featured wrappers that are capable of query rewriting takes time. Since our goal is to make SIOC data available for query and to entice people to use SIOC now, we need a method to allow querying of the information that sites publish in flat files. Replicating the contents of the entire site from the relational database to an RDF store may work initially and create an easy upgrade path. However, in the longer term, storing and integrating data in a native RDF repository is the desirable solution. Exporting data is quite simple because RDF does not restrict you in the way data can be expressed. On the flip side, the flexibility of RDF creates a problem when importing data into systems with a fixed schema. Issues arise here, for example, when an application is importing data using a given schema, and certain mandatory data is missing.

In the final section Breslin et al. talked about using SIOC Data. Given the ontology, the mappings, and the wrappers, they were now able to pose queries and add data to individual SIOC sites. They highlighted three aspects: browsing, querying and locating related information.

The authors concluded that to tackle the challenge of adoption they have provided an upgrade path that allows a gradual migration from existing systems to semantically-enabled sites. For combination with other ontologies they have presented mapping to and from SIOC.


Breslin et al. Towards semantically-interlinked online communities. The Semantic Web: Research and Applications (2005) pp. 500-514


About laurensdv
Computer Science Student, interested in creating more innovating user experiences for information access. Fond of travelling around Europe!

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