8.3.7 Compound Property Values Property values can be ▫Literals ▫Resource ▫Container ▫Collection, or… ▫Compound Value Compound Value ▫Has multiple value parts ▫1 part identified as primary value of the property ▫Lets properties describe “n-ary” relationships

Resource Parse Type rdf:parseType="Resource" ▫Tells parser to interpret the contained value as a an “in-line” resource ▫Identifies a compound value

Qualified Property Value rdf:value property ▫Identifies primary value within compound property value ▫Called the qualified property value ▫Can be a literal or a resource ▫Not required, but available Other properties describe qualified property value Example ▫ 2.5 USD

N3 Approach: exproduct:item10245 exterms:weight _:weight _:weight10245 rdf:value "2.4"^^xsd:decimal. _:weight10245 exterms:units exunits:kilograms. RDF/XML: ]> <rdf:RDF xmlns:rdf=" xmlns:exterms=" 2.4 Units Example XML and Graph Exproduct:item ^^xsd:decimal rdf:value exterms:weight Exunits:kilograms exterms:units

Qualified Property Practices rdf:parseType="Resource" ▫attribute is used to indicate that the contents of an element are to be interpreted as the description of a new (blank node) resource ▫Don’t have to write a nested rdf:Description element It is generally not safe to make the assumption that anyone accessing a property value will understand the units being used ▫So rdf:value is a recommended mechanism, alternatives:  Property value with units in name (i.e. weightInKg)  Properties to specify this information off main node (i.e. weightUnits)  …

8.3.8 Striped Syntax Nesting rdf:Description elements ▫Chains alternating property/value descriptions ▫Called “striping” ▫Creates a blank (anonymous) mode when parsed ▫Not recommended, because  Easier to read, but  Harder to edit and  More difficult to generate from automated tool Example ▫ Jorge Garcia

8.3.9 RDF Description Summary RDF/XML statements use rdf:Description ▫Subject can be either new or existing resource ▫Properties specify the predicate ▫Object (property value) can be Literal, Resource, Container, Collection, or Compound Value  Can “stripe” by using an “in-line” statement as the object of a property, but not recommended RDF/XML statements can usually be automatically generated from databases

8.4 RDF/XML Summary RDF/XML provides ▫Structured method for serializing RDF in XML ▫Mechanism for interchanging RDF content RDF resources ▫Declared & described using  rdf:Description element  Properties and property values

8.4 RDF/XML Summary cont’d CategoryConstructPurpose Resource identification rdf:ID attributeEstablishes reference identifier; “creates” resource (subject) rdf:about attributeReferences existing identifier (subject) rdf:resource attributeReferences existing identifier (object) rdf:value attributeIdentifies primary value in compound value rdf:type propertySpecifies class membership RDF listsrdf:_n propertyIndexed accessor rdf:li propertyConvenience accessor (assigns indices automatically) Containerrdf:Bag classUnordered container rdf:Seq classSequentially-ordered container rdf:Alt classContainer of alternatives from which one must be chosen Collectionrdf:List classList of items rdf:first propertyFirst item in a list or sub-list rdf:rest propertyRemaining items in a list or sub-list &rdf;nil resourceEmpty list used to terminate list

8.5 Why RDF/XML is not enough RDF/XML ▫Introduces some standardization to descriptions ▫Cannot describe more complex semantic relationships (especially classes) ▫Lacks concepts for enumeration and datatypes RDFS ▫Adds object-oriented features to RDF