Distributed Software Development
RDF
Chris Brooks
Department of Computer Science
University of San Francisco
Department of Computer Science — University of San Francisco – p. 1/??
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Resource Description Framework - Lecture Slides | CS 682, Study notes of Software Engineering
Material Type: Notes; Class: Distributed Software Develop; Subject: Computer Science; University: University of San Francisco (CA); Term: Spring 2006;
Typology: Study notes
Pre 2010
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Distributed Software Development
RDF
Chris Brooks Department of Computer Science University of San Francisco Department of Computer Science — University of San Francisco – p. 1/
RDF
- RDF stands for Resource Description Framework - Provides a way to describe properties that belong to objects. - Much like a relational database. - Can be serialized as XML, but it’s easiest not to get hung up onthe XML syntax initially. ◦ Built to be created and consumed by machines. Department of Computer Science — University of San Francisco – p. 2/
RDF’s data model
- Recall that XML produces a tree-structured data model. - This can make it hard to represent some sorts of knowledge. - How to denote that two elements share a sub-element? Department of Computer Science — University of San Francisco – p. 4/
Representation in XML
- For example:
Doors Break On Through Greatest Hits Doors Light My Fire Greatest Hits Devo Through Being Cool Greatest Hits Department of Computer Science — University of San Francisco – p. 5/
RDF’s data model
- From a set of RDF triples, we can construct an RDF graph. - Subject and value are nodes ◦ Nodes can be^ • URIs - a generalized form of a URL - blank nodes - mostly useful as placeholders - literals - strings, values, etc. ◦ ◦ Properties are edges. Department of Computer Science — University of San Francisco – p. 7/
Resources
- An RDF document is a set of statements about resources ◦ Documents, video clips, services - A resource is something that has a location. ◦ Referred to with a URI - The subject of an RDF statement is a resource. Department of Computer Science — University of San Francisco – p. 8/
Properties and statements
- A property is a relation between a subject and an object. - A statement is a subject, a property, and an object. - This allows RDF statements to be placed in a graph model. - We called this a semantic network in AI. Department of Computer Science — University of San Francisco – p. 10/
Reification
- It’s also possible in RDF to make statements about statements. - This process is called reification <rdf:Description rdf:ID=’’item10245’’> <exterms:weight rdf:datatype=’’&xsd;decimal’’>2.4</exterms:weight> </rdf:Description><rdf:Statement rdf:about=’’#triple12345’’> <rdf:subject rdf:resource=’’http://www.example.com/2002/04/product <rdf:predicate rdf:resource=’’http://www.example.com/terms/weight’ <rdf:object rdf:datatype=’’&xsd;decimal’’>2.4</rdf:object> <dc:creator rdf:resource=’’http://www.example.com/staffid/85740’’/ </rdf:Statement> - This lets you say things about who wrote a statement, when itwas added, the validity, and so on. Department of Computer Science — University of San Francisco – p. 11/