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Difference between revisions of "Attribute"
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== Definition == | == Definition == | ||
| − | * Defines a property of an [[ | + | * Defines a property of an [[Node]] or a [[Context]]. |
* Has a URI-valued type that: | * Has a URI-valued type that: | ||
| − | ** Identifies the [[Attribute]] instances with a given [[ | + | ** Identifies the [[Attribute]] instances with a given [[Node]] or [[Context]] |
** Identifies the [[Attribute]]'s [[Attribute Model]] | ** Identifies the [[Attribute]]'s [[Attribute Model]] | ||
* Has one or more values all of which MUST be unique | * Has one or more values all of which MUST be unique | ||
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==Examples== | ==Examples== | ||
| − | The physical | + | 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 [[Attribute]]s (and associated values) in this [[Context]]: |
* email-address = bob@portcontrol.gov | * email-address = bob@portcontrol.gov | ||
| − | * phone number = {617-555-1234, 617-333-4321} | + | * phone number = {617-555-1234, 617-333-4321} <-- multi-valued attribute example |
* passport information = ...etc. | * passport information = ...etc. | ||
* fingerprint data = ...etc. | * fingerprint data = ...etc. | ||
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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. | 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 [[ | + | 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 [[Attribute]]s: |
* platinumCustomer = True | * platinumCustomer = True | ||
* preferredColor = "blue" | * preferredColor = "blue" | ||
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==Open Issues== | ==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" | |
==Kinds of Attributes== | ==Kinds of Attributes== | ||
* [[Context Relation]] | * [[Context Relation]] | ||
* [[Context Correlation]] | * [[Context Correlation]] | ||
| − | * [[ | + | * [[Node Relation]] |
| − | * [[ | + | * [[Node Correlation]] |
==See Also== | ==See Also== | ||
Revision as of 21:18, 7 February 2008
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 that:
- Identifies the Attribute instances with a given 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 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"