**4. Explicit representation of an HR knowledge store**

To represent information on the Web and to ensure interoperability between applications that exchange machine-understandable information, the Semantic Web uses the Resource Description Framework (RDF) as a general-purpose language. RDF describes information in terms of objects ("resources") and the relations between them via the RDF Schema, which serves as a meta-language or vocabulary to define properties and classes of RDF resources. The next layer on top of the RDF/RDFS data model serves to formally define domain models as shared conceptualizations, also often called ontologies (Gruber, 1993). Ontologies are nowadays very often used for building integrated inter- and intraorganization business services, and to make the search and retrieval both efficient and meaningful. In this Section we will use the RDF and OWL languages to introduce the most important concepts and relations between concepts relevant for building an expert profile (see Figure 2).

Building Expert Profiles Models Applying Semantic Web Technologies 215

In a top-down manner, we can define the most general concepts/properties as subclasses / subproperties of entities from the public vocabularies FOAF, DOAC, and BibTeX (Aleman-Meza et al., 2007)and assign them meaning identical with the existing commonly used classes in the Semantic Web (see Table 2). In that way, the main "components" are defined as subclasses of the public concepts (*foaf:Person*, *foaf:Organisation*, *foaf:Document*, *foaf:PersonalProfileDocument*, *doac:Education*, *doac:Skill*, *doac:Experience, bibtex:Entry*), while links/relations between the components are defined as sub-properties of *foaf:interest*, *foaf:made/maker*, *foaf:topic*, *foaf:primaryTopic*, *foaf:homepage*, etc. Additional classes and properties specific to the domain of interest (e.g. in the ICT domain) can be defined manually with elements from the RDF Schema (www.w3.org/TR/rdf-schema/) or defined automatically in bottom-up manner e.g. using D2RQ server, http://www4.wiwiss.fu-

SIOC The SIOC initiative (Semantically-Interlinked Online Communities,

FOAF The FOAF (Friend of a Friend, http://www.foaf-project.org/)

DOAC DOAC (Description Of A Career, DOAC Vocabulary specification,

DOAP DOAP (Description of a Project, DOAP Vocabulary specification

Dublin Core The Dublin Core Metadata Initiative (http://dublincore.org/) is an

For example, the Mihajlo Pupin Institute ontology (MPI) uses concepts from the DOAC+FOAF vocabulary and extends them with new concepts and properties defined in

generated from a FOAF+DOAC file.

http://www.w3.org/Submission/2007/02/) aims to enable the integration of the online community information. SIOC provides the Semantic Web ontology for representing rich data from the Social

project is about creating a Web of machine-readable pages describing people, the links between them and the things they create

http://ramonantonio.net/doac/0.1/) is a vocabulary used for describing professional capabilities of a worker. It was designed to be compatible with the Europeans Curriculum so that those can be

(http://trac.usefulinc.com/doap/ ) is a RDF schema and XML vocabulary used for describing software projects and, in particular,

open organization engaged in the development of interoperable online metadata standards that support a broad range of purposes

berlin.de/bizer/d2r-server.

Table 2. RDF models

the *imp* and *skills* namespace as follows:

Acronym RDF model

Web in RDF.

and do.

open source.

and business models.

general description of an expert (*imp:Person rdfs:subClassOf foaf:Person*);

Fig. 2. UML representation of the concept Expert.
