Hi all, Could you please describe why we need ontology or OWL. When we are represeting data from RDF.

is that means that RDF cannot be machine proccessable? if we cannot use OWL

asked 25 Apr '11, 02:30

niran's gravatar image

niran
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In simple words RDF provides us a way to organize data in a graphical format and whereas OWL helps to add meaning to that data or add semantics to the data. RDF can be visualized as a database having a graphical orientation. It contains the resource that points to the data and contains vocabulary so as to give a common meaning to the data between two parties. Vocabulary refers to standard that is being followed and accepted by a group of people. Where as the OWL refers to a language which is used to add semantics to the RDF/XML document. That is it adds meaning and makes it machine readable. This helps software to easily utilize the data and identify it. Thus RDF could be considered as a Graphical database which relates one element to another using vocabulary and OWL adds meaning to the entire thing. I have a nice 30 mins tutorial that will help you understand better @ Digital Flicks

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answered 25 Apr '11, 07:58

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Roger
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Thank All, I got some idea regarding RDF, OWl and smeantic,

From your comment what I understood is, RDF is just like Data base table, which stores data Where as OWL is just like adding primary, foregin key to Table in data base.

is that correct

(27 Apr '11, 02:08) niran niran's gravatar image

yeah... it is .. we can say that it might be comparable. In actual situation what happens is that the data is being connected to different resources in a graphical fashion. Due to this it becomes easy to traverse data. And the best part of the entire story is that the data is actually mapped using URI for eg:

"niran hasProfileAt semanticWebCommunity"

http://example.com/niran http://profileOntoEx.com/profile#hasProfileAt http://answers.semanticweb.com/users/1360/niran

So above can be considered as a graphical representation of the above statement using URI's (links are an example)

(27 Apr '11, 13:21) Roger Roger's gravatar image

The above has three links that represent the as follows:-

Niran->http://example.com/niran hasProfileAt->http://profileontoex.com/profile#hasProfileAt semanticWebCommunity->http://answers.semanticweb.com/users/1360/niran

So you can see how Graphical structuse of linked data can benefit you when you use structured data. RDF is a solution to it. Hope this clears your doubt.

Please refer to the link http://shivkumarganesh.in/?p=6 This will direct you to a series of beginners tutorials. Wil be a kick start for you.

(27 Apr '11, 13:24) Roger Roger's gravatar image

As an example, vocabularies, ontologies, etc, help you and the machine in discovering new relationships that are not physically in the data that is described by RDF but is there in a "hidden" format. A typical case is if you describe subclass relationship between two classes then, via the associated 'rules' on subclasses, additional typing information can be deduced. In other cases vocabularies may help you finding inconsistencies in your data.

But you have to be careful... this does not necessarily mean that you have to use the full power of OWL for these, or that you have to build complex OWL ontologies. RDFS may be all you need; alternatively, SKOS or a very restricted form of OWL (e.g, OWL-RL) may be enough. In some other cases, due to the complexity of the application and the data you manage, complex OWL ontologies and reasoners may become necessary. Again in other cases you might be happy using a simple vocabulary plus one or two attached rules using RIF, SWRL, or N3... it all depends on your application!

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answered 25 Apr '11, 04:51

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Ivan
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Thanks Ivan,From your comment I understood in the following way,correct me if am wrong, ontologies are used to identify realtionship between RDF data so that we can avoid inconsistencies in RDF data modle, right?

is there any example or demo link so that I can explore on RDF and OWL

(25 Apr '11, 05:10) niran niran's gravatar image

Not "so that" but "or":-) ontologies may be used to reveal inconsistencies, and also may be used to identify 'hidden' relationships. The two are not mutually exclusive, but are not mutually dependent either, you can can concentrate on one and not on the other, for example.

It is fairly difficult to answer on your second request. What kind of demos do you refer to? Thanks to evolution there are so many applications, tools, primers, books, etc, around that it is almost impossible to point you at one single place...

(25 Apr '11, 05:17) Ivan Ivan's gravatar image

I think this book has a chapter that explains what Ivan is saying very well. http://www.amazon.com/Semantic-Web-Working-Ontologist-Effective/dp/0123735564

(26 Apr '11, 17:56) Ronald P. Reck Ronald%20P.%20Reck's gravatar image

The answers by Ivan are helpful in understanding OWL usage when there is RDF.

(02 Jan '13, 03:24) Isma Isma's gravatar image

Ignoring the OWL-part of your question, ontology is one of the things you can do with RDF. You can do ontology without RDF (e.g. Common Logic, First Order Logic, LISP, SKOS, Datalog), and you can use RDF without doing ontology (e.g. creating a graph database).

The OWL-part, then, is a particular package of language and logic that many people use to do ontology. I tend to do ontology in RDF without OWL, leaning on things like Jena rules, but there are plenty of times when it's convenient to leverage OWL content (e.g. owl:disjointWith).

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answered 25 Apr '11, 11:15

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Ryan Kohl
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question asked: 25 Apr '11, 02:30

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last updated: 02 Jan '13, 05:00