This link has been bookmarked by 49 people . It was first bookmarked on 16 Nov 2006, by Dave Dennis.
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24 Apr 13
tom_cq"RDF is a method for expressing knowledge in a decentralized world and is the foundation of the Semantic Web, in which computer applications make use of distributed, structured information spread throughout the Web. Just to get it out of the way, RDF isn't strictly an XML format, it's not just about metadata, it has little to do with RSS, and it's not as complicated as you think."
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09 Jan 13
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RDF is a method for expressing knowledge in a decentralized world and is the foundation of the Semantic Web, in which computer applications make use of distributed, structured information spread throughout the Web.
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a general method to decompose any type of knowledge into small pieces
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Similarly, RDF isn't just about how you write it. It's about representing network- or graph-structured information. You can write RDF in XML, and many people do.
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The first format above, called N3, is just as good.
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What makes RDF suited for distributed knowledge is that RDF applications can put together RDF files posted by different people around the Internet and easily learn from them new things that no single document asserted.
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URIs can have the same syntax or format as website addresses, so you will see RDF files that contain URIs like http://www.w3.org/1999/02/22-rdf-syntax-ns#type, where that URI is the global name for some entity. The fact that it looks like a web address is totally incidental.
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This point is important and needs repeating: Whatever their form, URIs you see in RDF documents are merely verbose names for entities, nothing more. Forget that it has anything to do with the web.
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Since URIs can be quite long, in various RDF notations they're usually abbreviated using the concept of namespaces from XML. That's what the colons are doing in :john, :hasMother, and the other entities in the example.
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26 Dec 12
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22 Nov 11
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20 Sep 11
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RDF is a general method to decompose any type of knowledge into small pieces, with some rules about the semantics, or meaning, of those pieces. The point is to have a method so simple that it can express any fact, and yet so structured that computer applications can do useful things with it
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XML can be abstracted beyond its written brackets-and-slashes notation to something more abstract, a "DOM" for tree-structured data. Similarly, RDF isn't just about how you write it. It's about representing network- or graph-structured information
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RDF is designed to represent knowledge in a distributed world
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Everything at all mentioned in RDF means something, whether a reference to something concrete in the world, an abstract concept, or a fact.
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first by linking documents together by the common vocabularies they use, and second by allowing any document to use any vocabulary.
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integrate data from different sources without custom programming
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offer your data for re-use
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decentralize data in a way that no single party "owns" al
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(browse, query, match, input, extract, ...)
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Subject, Predicate, Object
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A fact i
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entities
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global and refer to the same entity in any RDF document
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local, and the entity it refers to cannot be directly refered to outside of the RDF
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are always Uniform Resource Identifiers (URIs)
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Global names
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The fact that it looks like a web address is totally incidental
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URNs are a subtype of URI used for things like identifying books by their ISBN number
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TAGs are a genera
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URIs are used as global names because they provide a way to break down the space of all possible names into units that have obvious owners. URIs that start with http://www.rdfabout.net/ are implicitly controlled by me
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This point is important and needs repeating: Whatever their form, URIs you see in RDF documents are merely verbose names for entities, nothing more. Forget that it has anything to do with the web.
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Graphs consist of nodes interconnected by edges
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nodes are the computer
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edges are the ethernet wires
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edges are statements
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nodes are names
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27 Jan 11
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RDF is a general method to decompose any type of knowledge into small pieces
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RDF isn't just about how you write it. It's about representing network- or graph-structured information.
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RDF is designed to represent knowledge in a distributed world
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Standards built on RDF describe logical inferences between facts and how to search for facts in a large database of RDF knowledge.
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What makes RDF suited for distributed knowledge is that RDF applications can put together RDF files posted by different people around the Internet and easily learn from them new things that no single document asserted.
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first by linking documents together by the common vocabularies they use
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allowing any document to use any vocabulary
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So why use RDF
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- You want to integrate data from different sources without custom programming.
- You want to offer your data for re-use by other parties
- You want to decentralize data in a way that no single party "owns" all the data.
- You want to do something fancy with large amounts of data (browse, query, match, input, extract, ...), so you develop (or re-use) a generic tool that allows you to do this on top of the RDF data model (which has the advantage of not being tied to a proprietary data storage/representation technology, like a database dialect).
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Names come in two types. Global names, which have the same meaning everywhere, are always Uniform Resource Identifiers (URIs)
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The fact that it looks like a web address is totally incidental.
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There may or may not be an actual website at that address, and it doesn't matter. There are other types of URIs besides http:-type URIs
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URIs are used as global names because they provide a way to break down the space of all possible names into units that have obvious owners.
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This point is important and needs repeating: Whatever their form, URIs you see in RDF documents are merely verbose names for entities, nothing more. Forget that it has anything to do with the web.
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they're usually abbreviated using the concept of namespaces from XML
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Graphs consist of nodes interconnected by edges
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The name at the start of the arrow is the statement's subject,
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the name at the end of the arrow is the statement's object, and the name that labels the arrow is the predicate.
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distributed information
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What you should take away from this example is how unconstraining RDF is,
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They had to agree to use RDF, but they didn't have to agree on any specific data format or even on specific URIs
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