Introduction:
Ontologies are becoming popular because of what they promise:a share and common understanding that reaches across people and application systems.The notion of an ontology is becoming widespread in fields such as
- intelligent information integration
- cooperative information systems
- information retrieval
- electronic commerce
- knowledge management
Ontologies applied to the World Wide Web are creating the Semantic Web. XML lets developers define arbitrary domain and task specific extensions. The
resource description framework has taken an important additional step by defining a syntactical convention and a simple data model
for representing machine-processable data semantics. RDF is a standard for the Web metadata the World Wide Web Consortium (www.w3c.org/rdf) develops, and it defines a data model based on triples:
object, property, and value.
We took RDFS as astarting point and enriched it into a full-fledged Web-based ontology language called OIL. We included these aspects:
- A more intuitive choice of some of the modeling primitives and richer ways to define concepts and attributes.
- The definition of a formal semantics for OIL.
- The development of customized editors and inference engines to work with OIL.
The three main application areas of ontology technology:
Knowledge management:
- Searching information
- Extracting information
- Maintaining
- Automatic document generation
- Using ontologies, semantic annotations will allow structural and semantic definitions of documents
Web commerce:
- Automatic text recognition
- Ontology mappings translate different product descriptions
- Based on text extraction and format heuristics
- An ontology will describe the various products and help navigate and search automatically for the required information
Electronic business:
- XML, which is designed to close this gap in current Internet technology, drastically changes the situation.
- Standard ontologies must cover the various business areas
- Ontology-based translation services must link different data structures in areas
This language must meet three requirements:
- It must be highly intuitive to the human user
- It must have a well-defined formal semantics with established reasoning properties
to ensure completeness, correctness, and efficiency. - It must have a proper link with existing Web languages such as XML and RDF to
ensure interoperability.
Web standards:XML and RDF
- OIL has a well-defined syntax in XML based on a document type definition and an XML Schema definition.
- RDFS provides two important contributions: a standardized syntax for writing ontologies and a standard set of modeling primitives such as instance-of and subclass-of relationships.
OIL's layered architecture:
- Standard OIL aims to capture the necessary mainstream modeling primitives that provide adequate expressive power and are well understood.
- Instance OIL includes a thorough individual integration and a full-fledged database capability.
- Heavy OIL will include additional representational (and reasoning) capabilities.
OIL’s layered architecture has three advantages:
- An application is not forced to work with a language that offers significantly more
expressiveness and complexity than is needed. - Applications that can only process a lower level of complexity can still catch some of
an ontology’s aspects. - An application that is aware of a higher level of complexity can still understand
ontologies expressed in a simpler ontology language.
OIL has strong tool support in three areas:
- Ontology editors, to build new ontologies
- Ontology-based annotation tools, to link unstructured and semistructured information sources with ontologies.
- Reasoning with ontologies, which enables advanced query-answering services, supports ontology creation, and helps map between different ontologies.
