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Semantic Web

Semantic Web. Exam 1 Common Mistakes. RDFS (in T/F section). Semantic web technologies Is best for changing/evolving problem domains Not so great for static domains Most everyone got this correct! Domain and range – most people missed this Domain applies to subject, range applies to object

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Semantic Web

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  1. Semantic Web Exam 1 Common Mistakes

  2. RDFS (in T/F section) • Semantic web technologies • Is best for changing/evolving problem domains • Not so great for static domains • Most everyone got this correct! • Domain and range – most people missed this • Domain applies to subject, range applies to object • Transitive relationships – most everyone got this correct!!

  3. Ontologies (in T/F section) • VCARD • For personal business cards (pretty much contact info) • Dublin Core • For basic metadata – creators, dates, scope of creations/entities • FOAF • For friendships, working relationships to others, organizations, and groups

  4. Design Pattern Vocabulary • All from Lecture 4 –SubsetOfHeadsUpPatterns.ppt Pattern Categories Patterns

  5. RDF & RDF/XML • Draw graph from RDF/XML and N3 data • All RDF graphs are labeled, directed • So arrows are required • (Short) Labels on arrows are required • (Short) Labels in ellipses are required • Only blank nodes should not have labels • Literals must be in boxes (not ellipses) • N3 data is actually easier to read then RDF/XML • Spend the few minutes needed to learn it, if you haven’t • The number of triples is the number of links in an RDF graph! (Just count them)

  6. RDF & RDF/XML • A graph can have the same label coming from it any number of times (unless it has a constraint – which we haven’t discussed, yet) • Don’t make up blank nodes – they are a pain and only used as required • Note that containers (bag, seq, alt) include a rdf:type node and use _1, _2, etc

  7. SPARQL • Writing SPARQL SELECT queries • Query for all triples • Most everyone got this one!! • To write SPARQL queries, traverse the graph structure! • You must represent all search patterns in some sort of triple form • Two (isolated) elements does not make a triple • If your single path doesn’t cover all your cases, use a UNION • UNION requires curly braces around triple patterns • Put periods after triple patterns (although not required if followed by a curly brace or similar) • Parentheses are dangerous (i.e. they indicate a RDF list structure which terminates in Nil, not a set of triples) • Blank node handling and meaning • Handling containers - Query for one or more specific elements off the container (hint: use UNION) Especially consider Sparql_PopQuizAndInClassLab.ppt

  8. Reification • Meaning of reification • Meaning of metadata from reification node • Metadata attached to a reification node is in a context about one triple of interest • Creator in a reification node is ‘who said the triple’ • Metadata is ‘what he said about the triple’ • Meaning of multiple reification nodes • They provide metadata about a single triple. They do not create different facts.

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