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Attribute
Contents
Introduction
This page describes the Higgins concept of Attribute.
Definition
- Defines a property of an I-Node or a Context.
- Has a URI-valued type that:
- Identifies the Attribute instances with a given I-Node or Context
- Identifies the Attribute's Attribute Model
- Has one or more values all of which MUST be unique
- 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
Examples
The physical person Entity Bob Smith might be represented as an I-Node in the Context of his employer, the Port Control Authority. This I-Node 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}
- 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 Entity Bob Smith might also be represented as a I-Node 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"
HOWL
Open Issues
- 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 I-Node cannot have an attribute "names-of-children" whose values are "frank, frank, frank".
- We need to be able to describe the reality that "real world" context providers must restrict attributes to be "closed"