The Semantic Web is a way of describing things in the world and their relationships in a decentralized way. Resource Description Framework (RDF) is the key technology which enables computers to process some of the information humans take for granted when we write on the web about (for example) people, places, time, documents, and how these things relate to each other.
Semantic Web specifications are available from the W3C's Semantic Web page. SWAD-Europe has been very active in W3C specification development. Dan Brickley co-chaired the RDF Core working Group, which clarified the RDF specifications between 2001 and 2004; while other members worked on testcases and other documents within this group. Project members have also been active in the W3C Data Access Working Group, which has been deciding on a query language for RDF; others participate in the W3C Semantic Web Best Practices Working Group, which is working to write down some of the formal and informal knowledge about the creation and management of vocabularies, modelling techniques, and certain vocabularies themselves (e.g. Wordnet, thesauri).
There are many informal groups working in this area. The main one is the Semantic Web interest Group, a good place to ask questions, whether via the mailing list or the IRC channel. More information can be found on the ESW wiki, a community driven information source. Planet RDF is an informal place to keep track of webloggers in this area. SWAD-Europe team members are active in all these communities, and have sought to maintain an online presence in these areas in order to help answer questions from users and developers of the technologies. There are active communities in the specific areas of image annotation, calendaring, thesauri, geographical information, and information about people. There is also an active Spanish-speaking developer community. SWAD-Europe has a specific page about its role in community development.
Semantic Web vocabularies and ontologies are ways of describing the world and can be very broad (e.g. Wordnet, a dictionary) or very narrow (for example the Geo vocabulary, which only has three properties and one class). Good places to look for information on existing vocabularies are Schemaweb and Ontaria, and the Semantic Web Best Practices working group is working on notes about modelling ontologies and about maintaining vocabularies. SWAD-Europe work in this area has included significant work creating a thesaurus vocabulary and community, work towards a calendaring RDF vocabulary, and work on image description.
Many tools for creating, parsing and storing Semantic Web data are now available in multiple languages. A good starting point is Dave Beckett's RDF resource guide, tools section. SWAD-Europe has a tools page detailing work on tools support within the project, including work test cases for RDF query languages which input into the Data Access W3C Working Group and surveys of RDF APis and Tools for scalable storage of RDF data. SWAD-Europe also supported work on the Redland RDF application framework.
Developers were the main focus of SWAD-Europe's outreach work, and details of the ten developer workshops held as part of the project can be found on the community building page. SWAD-Europe held workshops on Calendaring, image annotation, Dublin Core, and FOAF and Social Software among other topics.