This link has been bookmarked by 74 people . It was first bookmarked on 28 Jun 2006, by Arnold Bailson.
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28 Nov 14
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16 Mar 13
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Identifiers
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To identify items on the Web, we also use identifiers
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or URIs for short
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Uniform Resource Identifiers
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one form of URI: the URL or Uniform Resource Locator
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URIs are decentralized
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you don't need anyone's permission to create a URI
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Extensible Markup Language (XML)
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simple way to send documents across the Web
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can include markup
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machine-readable
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<sentence>
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<animal>
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href="http://aaronsw.com/"
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</animal>.
</sentence> -
<person
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</person>
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uniquely identify my markup elements
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So I assign a URI to each of my elements
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and attributes
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<sentence
xmlns="http://example.org/xml/documents/"
xmlns:c="http://animals.example.net/xmlns/"
><c:person c:href="http://aaronsw.com/"> -
<c:animal>
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</c:animal>.</sentence>
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</c:person>
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Resource Description Framework (RDF)
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machine-processable.
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three parts: a subject, a predicate and an object.
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An RDF statement is a lot like a simple sentence, except that almost all the words are URIs
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where do we expect all this RDF information to come from? The most likely source is databases.
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Schemas and Ontologies: RDF Schemas, DAML+OIL, and WebOnt
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14 Feb 12
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A common practice for creating URIs is to begin with a Web page. The page describes the object to be identified and explains that the URL of the page is the URI for that object. For example, I wanted to create a URI for my copy of "Weaving the Web" by Tim Berners-Lee. First, I created a Web page that describes my copy. Second, I noted on that page that the URL for the page serves as the URI for my copy of the book. By doing this, I've associated that URI (http://logicerror.com/myWeavingTheWeb) with my copy of "Weaving the Web." Creating a URI can be just this simple.
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28 Mar 11
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04 Mar 11
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01 Feb 11
John Pearce"This piece speaks about the different parts of the Semantic Web and how they fit together. For a high-level interview, take a look at Sandro Hawke's The Semantic Web (Put Simply). On the other hand, if you're a Web developer who's interested in building Semantic Web Sites or Semantic Web Services, check out The Semantic Web (for Web Developers). Now back to your regularly scheduled article."
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29 Jan 11
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28 Dec 10
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The smartest are "heuristic engines" which follow all these rules and statements to draw conclusions, and kindly place their results back on the Web as proofs, as well as plain old data.
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Tim Berners-Lee has proposed an "Oh, yeah?" button, that when clicked would have your computer attempt to provide reasons to trust the data. But whether you decide for yourself or leave it up to your computer, the information necessary to make an informed decision is available to you via the Web of Trust.
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21 Feb 10
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22 Dec 09
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13 Jul 09
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30 Dec 08
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03 Sep 08
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19 Jul 08
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A URI is not a set of directions telling your computer how to get to a specific file on the Web (though it may also do this). It is a name for a "resource" (a thing). This resource may or may not be accessible over the Internet. The URI may or may not provide a way for your computer to get more information about that resource.
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should not assume that a URI does anything more than provide an identifier for a resource.
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there's no way for a computer or human to figure out what a specific term means, or how it should be used. The use of all these URIs is useless if we never describe what they mean. This is where schemas and ontologies come in. A schema and an ontology are ways to describe the meaning and realtionships of terms. This description (in RDF, of course) helps computer systems use terms more easily, and decide how to convert between them.
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16 May 08
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22 Apr 08
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26 Mar 08
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Because anyone can create a URI, we will inevitably end up with multiple URIs representing the same thing. Worse, there will be no way to figure out whether two URIs refer to exactly the same resource.
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the URL of the page is the URI for that object.
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A URI is not a set of directions telling your computer how to get to a specific file on the Web (though it may also do this). It is a name for a "resource" (a thing). This resource may or may not be accessible over the Internet.
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The URI may or may not provide a way for your computer to get more information about that resource.
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By including machine-readable meaning in our documents, we make them much more powerful.
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if I simply marked the words as "in italics", the computer has no way of knowing why those words are in italics. Is it for emphasis or simply for a visual effect?
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<sentence>
<person href="http://aaronsw.com/">I</person> just got a new pet <animal>dog</animal>.
</sentence> -
"I just got a new pet dog." This tells the computer that "I just got a new pet dog" is a "sentence," but -- importantly -- it does not tell the computer what a sentence is
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How is my computer to keep these straight?
To prevent confusion, I must uniquely identify my markup elements
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Uniform Resource Identifier
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RDF gives you a way to make statements that are machine-processable. N
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n RDF statement is a lot like a simple sentence, except that almost all the words are URIs
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<http://aaronsw.com/> <http://love.example.org/terms/reallyLikes> <http://www.w3.org/People/Berners-Lee/Weaving/> .
Can you guess what this says? The first URI is the subject. In this instance, the subject is me. The second URI is the predicate. It relates the subject to the object.
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RDF statements can say practically anything, and that it doesn't matter who says them.
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an important RDF principle, namely "anything can say anything about anything"
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<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:love="http://love.example.org/terms/" > <rdf:Description rdf:about="http://aaronsw.com/"> <love:reallyLikes rdf:resource="http://www.w3.org/People/Berners-Lee/Weaving/" /> </rdf:Description> </rdf:RDF>
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The most likely source is databases.
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In the world there are thousands of databases, most containing interesting machine-processable information. Governments store arrest records in databases; companies store part and inventory information in a database; most computerized address books store people's names and phone numbers in -- you guessed it! -- a database
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RDF is ideally suited for publishing these databases to the Web.
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, we can ask questions of all these databases at once:
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The use of all these URIs is useless if we never describe what they mean. This is where schemas and ontologies come in
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The coming Semantic Web will multiply this versatility a thousandfold.
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One of the best things about the Web is that it's so many different things to so many different people.
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For some, the defining feature of the Semantic Web will be the ease with which your PDA, your laptop, your desktop, your server, and your car will communicate with each other. For others, it will be the automation of corporate decisions that previously had to be laboriously hand-processed. For still others, it will be the ability to assess the trustworthiness of documents on the Web and the remarkable ease with which we'll be able to find the answers to our questions -- a process that is currently fraught with frustration.
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26 Dec 07
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29 Oct 07
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24 Oct 07
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07 Oct 07
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10 Aug 07
Judy O'ConnellThis piece speaks about the different parts of the Semantic Web and how they fit together.
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02 Aug 07
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18 Jul 07
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05 Jul 07
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04 Jun 07
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If I want to discuss something, I must first identify it.
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Because we use a uniform system of identifiers
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because each item identified is considered a "resource,"
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we call these identifiers "Uniform Resource Identifiers" or URIs for short
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Unlike most other forms of URIs, a URL both identifies and locates.
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While some URI schemes (such as
http:) depend on centralized systems (such as DNS), other schemes (such asfreenet:) are completely decentralized. -
we'll never be able to say with certainty exactly what a given URI means.
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A common practice for creating URIs is to begin with a Web page.
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a URL is a type of URI that does provide a way to get information about a resource, or perhaps to retrieve the resource itself, and other methods for providing information about URIs and the resources they identify are under development.
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Sometimes it is useful to provide more information about the content of an element than we can provide with the name of the element alone.
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Now the computer can't actually "understand" what you said, of course, but it can deal with it in a way that makes it seem like it does.
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an important RDF principle, namely "anything can say anything about anything"
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Information is spread across the Web, and two people can even say contradictory things
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Now, to write RDF like that is not the easiest thing in the world, and it seems unlikely that everyone will start speaking this strange new language anytime soon. So where do we expect all this RDF information to come from? The most likely source is databases.
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RDF is ideally suited for publishing these databases to the Web. And when we put them on the Web, we give everything in the database a URI, so that other people can talk about it too. Now, intelligent programs can begin to fit the data together. Using the available information, the computer can begin to connect the Bob Jones whose phone number is in your address book with the Bob Jones who was arrested last week and the Bob Jones who just ordered 100,000 widgets. Now, we can ask questions of all these databases at once: "Get me the phone number of everyone who ordered more than 1,000 widgets and was arrested in the last 6 months."
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ed:hasAuthor
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if anyone can say anything. Who would trust such as system?
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digital signatures provide proof that a certain person wrote (or agrees with) a document or statement
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So I digitally sign all of my RDF statements. That way, you can be sure that I wrote them
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tell your program whose signatures to trust and whose not to. Each can set their own levels or trust (or paranoia) the computer can decide how much of what it reads to believe.
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"Web of Trust"
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you trust your best friend, Robert
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rusts quite a number of people. And of course, all the people he trusts, trust another set of people
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And each of these relationships has a degree of trust (or distrust) associated with it.
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Note that distrust can be as useful as trust.
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Tim Berners-Lee has proposed an "Oh, yeah?" button, that when clicked would have your computer attempt to provide reasons to trust the data.
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the information necessary to make an informed decision is available to you via the Web of Trust.
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the defining feature of the Semantic Web will be the ease with which your PDA, your laptop, your desktop, your server, and your car will communicate with each other.
-
it will be the ability to assess the trustworthiness of documents on the Web and the remarkable ease with which we'll be able to find the answers to our questions
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25 May 07
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07 May 07
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06 May 07
avivajazz jazzavivaThis piece speaks about the different parts of the Semantic Web and how they fit together. For a high-level interview, take a look at Sandro Hawke's The Semantic Web (Put Simply). On the other hand, if you're a Web developer who's interested in building S
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11 Mar 07
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05 Mar 07
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Unlike most other forms of URIs, a URL both identifies and locates
-
While some URI schemes (such as
http:) depend on centralized systems (such as DNS), other schemes (such asfreenet:) are completely decentralized -
we will inevitably end up with multiple URIs representing the same thing. Worse, there will be no way to figure out whether two URIs refer to exactly the same resource.
-
A URI is not a set of directions telling your computer how to get to a specific file on the Web (though it may also do this). It is a name for a "resource" (a thing). This resource may or may not be accessible over the Internet.
-
should not assume that a URI does anything more than provide an identifier for a resource
-
machine-readable
-
anyone can create their own tags and mix them with tags made by others
-
uniquely identify my markup elements. And what better way to identify them than with a Uniform Resource Identifier? So I assign a URI to each of my elements and attributes
-
RDF gives you a way to make statements that are machine-processable
-
anything can say anything about anything
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two people can even say contradictory things
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RDF specification defines an XML representation of RDF, which is a bit more complicated
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Few (if any) database systems are ready for the messiness of the Web
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Whatever the cause, almost everyone can find a reason to support this grand vision of the Semantic Web. Sure, it's a long way from here to there -- and there's no guarantee we'll make it -- but we've made quite a bit of progress so far. The possibilities are endless, and even if we don't ever achieve all of them, the journey will most certainly be its own reward.
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computer systems use terms more easily, and decide how to convert between them
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is a subclass (type) of
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systems that follow logic, it makes sense to use them to prove things
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While it's very difficult to create these proofs (it can require following thousands, or perhaps millions of the links in the Semantic Web), it's very easy to check them.
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d igital signatures provide proof that a certain person wrote (or agrees with) a document or statement >
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Web of Trust
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describe the meaning and realtionships of terms
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27 Feb 07
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07 Feb 07
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23 Jan 07
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28 Oct 06
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11 Oct 06
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06 Sep 06
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31 Jul 06
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06 Jun 06
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21 Apr 06
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28 Feb 06
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27 Feb 06
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21 Oct 05
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28 Jun 05
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08 Feb 05
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This piece speaks about the different parts of the Semantic Web and how they fit together.
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11 Dec 04
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08 Nov 04
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27 Oct 04
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27 Sep 04
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18 Sep 01
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