The Semantic Web can be seen as an extension of the current one, in which information is given a formal meaning, better enabling computers to understand such information and handle it in a smarter manner.

In order to give to the content of Web resources a formal, computer understandable, meaning and make possible the Semantic Web vision, we need to add semantic metadata to such Web resources. The process of adding semantic metadata to Web resources is commonly referred as semantic annotation. In general, the semantic annotation of a Web resource requires to relate, to link, its whole content or a part of it (for instance one word, a frame of a video, or a part of an image) with a certain concept identifier (usually an URI, Uniform Resource Identifier), taken from an ontology or other knowledge source. Semantic annotation has a critical importance in order to make the Semantic Web become a reality.

The SQA, Semantic Query-based Annotation system presents a collaborative approach to semantic annotation which tries to take advantage of the effort of the millions of users who every day look for information on the Web using Web search engines as Google. In order to do so, the system integrates the semantic annotation task with the keyword-based information retrieval task familiar to most Web users. The annotation process in SQA requires that the users annotate their queries instead of annotating directly the contents of the Web resources. The keywords in the annotated queries are send to classical Web search engines as Google and a list of relevant resources for the user query are shown to the user. By clicking on a button, the user can say which resources are relevant for his/her query. By doing so, the concepts annotating the query are associated to the Web resource and a new annotation is defined.

Apart from integrating semantic annotation with habitual user actions, other of the characteristics of SQA is the usage of Wikipedia as semantic source in the semantic annotation process. Some of the advantages of this approach are:

• The wiki approach of Wikipedia makes easy the process of semantic source maintenance (you don't need to be a knowledge engineer to create a new Wikipedia entry) and at the same time assures that the contents of a certain page are the result of a community agreement.
• You can annotate your Web page at authoring time simply by using a link to Wikipedia.
• There are several versions of Wikipedia in several languages and the different language versions of a certain page are connected through links, in that sense we can say that Wikipedia is a multilingual semantic source.
• If we use Wikipedia pages as representations of concepts, then to find a certain concept in the semantic source (for instance, to annotate a certain piece of information) we can use the capabilities of current Web search engines as Google or Yahoo.

The SQA approach has also been sucessfully integrated with the Gnowsis semantic desktop. More information on this can be found on the SQA4Desktop homepage.