Abstract
The novel paradigm of social semantic bookmarking combines the positive aspects of semantic annotation with those of social bookmarking and tagging while avoiding their respective drawbacks; drawbacks such as the lacking semantic precision of tags or the cumbersome maintenance of ontologies. Social semantic bookmarking tools allow for the annotation of Internet resources based on an ontology and the integrated maintenance of the ontology by the same people that use it. This chapter motivates social semantic bookmarking by examining the respective problems of tag based bookmarking and semantic annotation. Social semantic bookmarking is then introduced and explained using the SOBOLEO application as an example. It also gives an overview of existing applications implementing this new paradigm and makes predictions about its movement into the mainstream and remaining research challenges.
TopIntroduction
An important challenge for today’s internet users is the recovery of internet resources that they had once found interesting and useful; as well as the discovery of new interesting information. Social bookmarking systems (such as delicious1) can aid in these tasks by supporting users in the collection, management and sharing of bookmarks; i.e. references to such resources and information. For organization, navigations and searching these systems utilize tags.
Tags are arbitrary keywords that are used by the users to further describe the internet resources in order to aid their retrieval. Tags are renowned for their flexibility and ease of use, because just any tag can be used and there is no overhead for vocabulary management. However, this missing structure is also the root cause for a number of problems plaguing tagging and hampering tag-based retrieval: problems such as typos, tags on different levels of abstraction, or synonyms. Replacing tags with annotations based on a controlled vocabulary or ontology can help alleviate these problems.
Systems that use ontologies as source for annotating internet resources are, however, also not without their problems. For one they are often cumbersome to use; but more importantly, they view ontology creation as a process separate from its use; a process performed by people different from those that use it. Another problem is that these systems often assume that the ontology stays unchanged for prolonged periods of time and requires only occasional updates. All this leads to unsatisfied users being confronted with out-of-date, incomplete, inaccurate and incomprehensive ontologies that they cannot easily use for annotation; this problem is particular acute in fast changing domains (Hepp, 2007).
The novel paradigm of Social Semantic Bookmarking combines the positive aspects of semantic annotation with those of social bookmarking while avoiding their respective drawbacks. Social semantic bookmarking tools allow for the annotation of internet resources with respect to an ontology and the integrated maintenance of the ontology by the same people that use it. Through the use of state-of-the-art web technologies such as bookmarklets and AJAX (e.g., for autocomplete functionality), these systems make ontology-based annotation of web documents as simple as tagging. Through easy-to-use, lightweight web ontology editors that are integrated into the system, the barrier between ontology creation and use is removed; users who annotate with the help of the ontology are the same who continuously evolve this ontology. Because internet resources are annotated with concepts (and not keywords), the problems of homonyms, synonyms etc. are avoided.
We present Social Semantic Bookmarking using the example of our system SOBOLEO (SOcial BOokmarking and Lightweight Engineering of Ontologies) – a system combining the above mentioned features with an innovative search engine and functionality supporting the discovery of experts on specific topics based on their interaction with the system. We also shortly discuss other social semantic bookmarking systems such as Bibsonomy, int.ere.st, GroupMe!, Fuzzy, and Annotea. Finally, we sketch the trends that shape the future of social bookmarking – one of the most visible and best known developments of the Web 2.0 world.
Key Terms in this Chapter
Semantic Tagging: Semantic Tagging is the process of associating an element from an ontology with some document, usually a computer file or website. Semantic tagging serves the goal of describing a document in order to facilitate better retrieval later on. Semantic tagging also helps to integrate the tagged document with other resources that are also related to the same ontology. Semantic tagging is a special kind of annotation.
Social tagging: Social tagging is the process of tagging and use of tagged resources in the context of systems that bring together the tags from a group of people for improved retrieval and in order to foster relationships between the users. Social tagging systems allow to discover other users by finding people that tagged the same resource or use the same tag. These systems also support the discovery of new information using the set of all tags made by all users.
Annotation: An annotation is extra information that is associated with some data, usually a document or website. Common uses of annotation are keywords associated to images that aid retrieval or comments about the quality of (parts of) the document in question. An annotation is normally added after the creation of a document and mostly created by other people than the initial author. The verb 'to annotate' refers to the process of adding an annotation to some document. An annotation is a special kind of meta-data, distinguished by the property of mostly being added later; however, the difference between annotation and meta-data is not clear cut.
Semantic Web: The vision of improving the internet making the content of the web more accessible to machines, this should enable agents to handle more complex task on behalf of the user. The Semantic Web initiative has given rise to standards such as RDF, OWL and SPARQL that aim to make representing information and exchanging information on the web possible.
Meta-Data: Meta data is data about data; extra information associated with some data, for example a document or website. Common uses of meta-data are creation dates and access right associated with files or information about the tool that was used to create a particular file. Meta-Data is often created at the same time as the data it describes, but can also be created at some later time. Meta-Data can be both embedded in the data it describes or external to it.
Tagging: Tagging is the process of associating a keyword or term (a 'Tag') with some document, usually a computer file or website. Tagging serves the goal of describing a document in order to facilitate better retrieval later on. The tags used in tagging are usually chosen informally by the person doing the tagging. Tagging is a special kind of annotation.
RDF: Resource Description Framework, a W3C specification for a data exchange format that can support decentralized meta-data exchange on a global scale. RDF is built on the idea of triples that are used to represent everything. A triple consists of a subject, a predicate and an object and represents one statement that is made about the relation between resources. An example for a triple would be 'Mike has type Human'.
SKOS: The Simple Knowledge Organisation System is a RDF vocabulary for the representation of different kinds of structured vocabulary such as thesauri, taxonomies or subject-heading systems. SKOS is build on top of RDF.
SOBOLEO: SOcial BOokmarking and Lightweight Engineering of Ontologies is a system for the webbased collaborative engineering of SKOS ontologies and annotation of internet resources. SOBOLEO enables the simple creation, extension and maintenance of ontologies. At the same time it supports the annotation of internet resources with elements from this ontology