1. Comparison of data facilities RelationalXMLWeb Repn.2-d arraytreeglobally accessable pages Data typingSQL, vendor extension XSchemabrowser conventions: links, images, script, … Relationskeys: foreign  primary IDREF, XPointer, XLink href Namespacedata dictionary: table, field names xmlnsURN (uniform resource name) Schemarelational schemaXSchemaXHTML, plus good luck. Activityembedded SQL triggers (SQL99) PI external application scripting IntegrityRelational integrity enforced Validation voluntarybrowsers mostly ignore.

2. Semantic Web See Scientific American article How to express intended meaning of data Directed graph represented as a triples (resource,predicate (property),object) –(CS639, Teacher, "Robert A. Morris") Resource must have a URI

3. CS639 Robert A. Morris Teacher

4. RDF Robert A. Morris or Latter form doesn't support more structure for Teacher Course should refer to an XSchema

5. RDF http://… /gradCourse/#639 Robert A. Morris Name S/3/075 Office http://…/~ram S/2/065 Teacher Room

6. RDF Robert A. Morris S/3/075

7. RDF <rdf:Description about=http://www.cs.umb.edu/~ram Course:Name="Robert A. Morris" Course:Office="S/3/075" />

8. RDF <rdf:RDF xmnls:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmnls:Course="http://www.cs.umb.edu/schemas/Course" <rdf:Description about="http://www.cs.umb.edu/~ram" Course:Name="Robert A. Morris" Course:Office="S/3/075" />

9. Types <rdf:RDF xmnls:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmnls:Course="http://www.cs.umb.edu/schemas/Course" <rdf:Description about="http://www.cs.umb.edu/~ram" rdf:type= "http://www.cs.umb.edu/schemas/Course/Person" Course:Name="Robert A. Morris" Course:Office="S/3/075" />

10. Processing resource descriptions A central point about RDF is to be able to reason about and otherwise process descriptions. I.e., want to talk about the properties of descriptions, such as –are they true? –where are they asserted? –If a certain statement is true, should some other thing also be true? Turning a Description into the kind of thing that can itself be described is called reification

11. Beyond RDF: The Semantic Web; interpreting information Thesaurus: synonyms Ontology: in philosophy, the study of things that can be described and their relationships. In CS: concepts and their relationships Knowledge base (facts base): sentences that are true or accepted as hypothesis