# The State Of The Art: Ontology Webbased Languages: Xml Based

Mohammad Mustafa Taye Department of Software Engineering Faculty of Information Technology Philadelphia University, Amman, Jordan Abstract - Many formal languages have been proposed to express or represent Ontologies, including RDF, RDFS, 
DAML+OIL and OWL. Most of these languages are based on XML syntax, but with various terminologies and expressiveness. 

Therefore, choosing a language for building an Ontology is the main step. The main point of choosing language to represent Ontology is based mainly on what the Ontology will represent or be used for. That language should have a range of quality support features such as ease of use, expressive power, compatibility, sharing and versioning, internationalisation. This is because different kinds of knowledge-based applications need different language features. The main objective of these languages is to add semantics to the existing information on the web. The aims of this paper is to provide a good knowledge of existing language and understanding of these languages and how could be used. Index Terms - Ontology, Ontology language, RDF, RDFS, DAML+OIL , OWL

## 1 Introduction

Ontologies become a critical part in many areas, especially in Web Semantics. Consequently, a number of representational formats have been proposed to support and express them completely. 

 Current languages used to express Ontologies fall generally into three categories [1]: 
vocabularies of Ontology defined using natural language, frame-based languages used to build the structure of Ontologies based on explicit statements of class and slot, and those languages based on logic, such as Description Logics. 

 The main object of semantic web languages is to add semantics to the existing information on the Web. RDF/RDFS [7], OIL [14], DAML+OIL 
[9], and OWL [2] are modelling web languages that have already been developed to represent or express Ontologies. In general, most of these languages are based on XML [16] syntax, but they have different terminologies and expressions. Indeed, some of these languages have the ability to represent some logical relation but others do not. Because some languages have greater expressive power than others, languages chosen for representing Ontologies are based mainly on what the Ontology represents or what it will be used for. In other words, different kinds of Ontological knowledge-based applications need different language facilitators for enabling reasoning on Ontology data. These description languages provide richer constructors for forming complex class expressions and axioms. 

 In fact, recently most Ontology developers have used Ontology Editors, which are environments or tools used directly for editing, developing or modifying Ontologies. These tools are used for providing support for the Ontological development process, as well as for conceptualising the Ontology; they transform the conceptualisation into executable code using translators. So the output Ontology of these tools will be in one of the Web Ontology languages supported by editors Such as Protégé [18], OWLP [21] and OilEd [22]. Alternatively Ontology reasoners are used to check the conflicts with a high degree of automation. Many such systems, including RACER [19] and FaCT [20], have been developed recently. 

 Returning to the main concern of this section, modelling web languages, there are in general two different types of language: Presentation languages such as HTML, designed to represent text and images to users or requesters without reference to the content, and Data Languages, intended to be processed by machines. The present research relates to the latter. 

 Before OWL, much research has been conducted into creating a powerful Ontology modelling language. This research stream began with the XML-based RDF and RDF/S, 