Category Archives: Semantic Web

OWL- Web Ontology Language

Web Ontology Language (OWL) is a language for defining and instantiating web ontologies (a W3C Recommendation). OWL ontology includes description of classes, properties and their instances. OWL is used to explicitly represent the meaning of terms in vocabularies and the relationships between those terms. Such representation of terms and their interrelationships is called ontology. OWL has facilities for expressing meaning and semantics and the ability to represent machine interpretable content on the Web. OWL is designed for use by applications that need to process the content of information instead of just presenting information to humans. This is used for knowledge representation and also is useful to derive logical consequences from OWL formal semantics.

OWL Sub-languages

OWL provides three increasingly expressive sub-languages designed for use by specific communities of implementers and users:-
(i) OWL Lite (is least expressive, suitable for simple class hierarchy and simple constraints and useful for quick migration path for thesauri and other taxonomies),
(ii) OWL DL (is more expressive, retains Computational Completeness that is, all conclusions are guaranteed to be computable and has Decidability that is, all computations will finish in finite time, and is based on Description Logic),
(iii) OWL Full (is most expressive and has syntactically freedom of RDF and has no computational guarantees but allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary and is not suitable for auto-reasoning).

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Difference Between “URL” and “URI”

Some of us (including me) can’t differentiate between URL and URI. We are often using URL and URI. So that’s why I search on internet and find some useful information. And I thought that I should share it with u. Any suggestions and comments are appreciated

URI – Uniform Resource Identifier

URL – Uniform Resource Locator


A URI identifies a resource either by location, or a name, or both. More often than not, most of us use URIs that defines a location to a resource. The fact that a URI can identify resources by both name and location has lead to a lot of the confusion in my opinion. A URI has two specializations known as URL and URN.


A URL is a specialization of URI that defines the network location of a specific resource. Unlike a URN, the URL defines how the resource can be obtained. We use URLs every day in the form of, etc. But a URL doesn’t have to be an HTTP URL, it can be, smb://, etc.


A URI is an identifier for some resource, but a URL gives you specific information as to obtain that resource. It is now considered incorrect to use URL when describing applications. Generally, if the URL describes both the location and name of a resource, the term to use is URI. Since this is generally the case most of us encounter every day, URI is the correct term.

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