Difference between revisions of "Attribute"

Revision as of 16:51, 31 January 2008

Definition

• Defines a property of an Entity or a Context.
• Has a URI-valued type which:
  • identifies the Attribute instances with a given Entity or Context
  • identifies the Attribute's Model
• Has one or more values
• The types of the values of an Attribute may be:
  • XML-Schema-based literal datatypes (a specific sub-set of the XML Schema literal types)
  • Sub-types of the XML-Schema-based literal datatypes
  • Complex (structured) datatypes
• The set of values of a single Attribute may be any combination of the value types

Attribute Model

• Defines the valuetype(s) of its value(s) (e.g. valuetype="string" or valuetype="directory string")
• Min Cardinality (e.g. this Attribute can have a minimum of 3 values)
• Max Cardinality
• Cardinality

Attribute Value Model (AVM) (e.g. directory string)

• May specialize:
  • a base XML Schema type (e.g. String) for literal AVMs
  • OR a complex AVM
  • OR another AVM
• Defines a set of constraints on its value(s) including:
  • Value must be one of {"red", "green", "blue"}
  • Syntax constraints (e.g. regular expression)

Details

• Even if all values are literals, they may differ in specific literal datatype (e.g. strings and integers may be intermixed)
• A special kind of Attribute is called a Relation whose value is a reference to another Digital Subject in the same or a different Context
• Some Attributes are defined by the containing Context's schema to allow multiple unique values. For example the attribute preferredBreakfast might have the values {spam, eggs}, but it could not have the values {spam, spam, spam, eggs, spam}.

Examples

The physical 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 Identity Attributes (and associated values) in this context:

• email-address = bob@portcontrol.gov
• phone number = {617-555-1234, 617-333-4321}
• 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 physical person Bob Smith might also be represented as a 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 Identity Attributes:

• platinumCustomer = True
• preferredColor = "blue"

HOWL

In Higgins

See Also

• Higgins Home
• Concepts
• Higgins Data Model