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Attribute
Contents
Introduction
This page describes the Higgins concept of Attribute.
Definition
- Defines a property of an Node or a Context.
- Has a URI-valued type
- Values
- Has one or more values all of which MUST be unique
- The types of the values of an Attribute are indicated by a URI
- The allowed value(s) are defined by an Data Range
Kinds of Attributes Defined in HOWL
Examples
The physical Entity Bob Smith might be represented as a Node in the Context of his employer, the Port Control Authority. This 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} <-- 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 Entity Bob Smith might also be represented as a 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 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"