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Attribute

Revision as of 08:32, 11 April 2008 by Asafronkova.aquasoft.dp.ua (Talk | contribs) (Undo revision 91866 by Asafronkova.aquasoft.dp.ua (Talk))

{{#eclipseproject:technology.higgins}}

Higgins logo 76Wx100H.jpg

Introduction

This page describes the Higgins concept of Attribute.

Definition

  • Defines a property of an Node or a Context.
  • Has a type (URI)
  • 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 Nodes

Implementation note: Complex values are likely stored internally as NodeId Data Range URIs that are dereferenced to produce Node instances.

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

  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 Node 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"


See Also

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