Difference between revisions of "Attribute"

Revision as of 14:41, 1 September 2008

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This page describes the concept of Attribute used in Context Data Model 1.1

Definition

• Defines a property of an Entity (or Context).
• Has one or more values all of which MUST be unique
• Has either simple or complex value(s)
• Simple values:
  • Are literal values (e.g. "green") based on a "base" XML Schema type URI (e.g. string)
  • The allowed value(s) are defined by a Data Range (URI)
• Complex values are Entities
• The values are identified by an Attribute UDI. This Attribute UDI can also be dereferenced to an Attribute Definition that provides metadata about this kind of Attribute.

Relationship to RDF/OWL

• The values of an attribute are the union of all objects O found in all RDF {subject, predicate, object} triples {S, P, O} such that S is the id of the Entity (or Context) in question and P is the Attribute UDI string value.

Kinds of Attributes Defined in CDM

• Entity Relation
• Entity Correlation
• Context Relation
• Context Correlation

Examples

The person Bob Smith might be represented as an Entity in the Context of his employer, the Port Control Authority. This Entity might have the following types of Attributes (and associated values) in this Context:

• email-address = bob@portcontrol.gov
• phone number = {617-555-1234, 617-333-4321} <-- multi-valued attribute example
• passport information = ...etc.
• fingerprint data = ...etc.
• surname = "Smith"

The surname Attribute in the example above might have a type of http://openschemas.org/2006/person/surname. The schema associated with the containing Context provides metadata about this URI.

This same Bob Smith might also be represented as an Entity in a "customer-to-Clothes-R-Us" Context (this customer's relationship with the Clothes-R-Us merchant. In this Context Bob has these Attributes:

• platinumCustomer = True
• preferredColor = "blue"

Open Issues

1. At present an Attribute cannot have N>1 values if the values are the same. For example a very odd father might name each of his three kids "frank". Thus the father Entity cannot have an attribute "names-of-children" whose values are "frank, frank, frank".
2. We need to be able to describe the reality that "real world" context providers must restrict attributes to be "closed"