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| + | #REDIRECT [[Higgins Data Model 1.0]] |
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| − | == Version 1.0 ==
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| − | * This page describes the Higgins 1.0 Context Data Model
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| − | * See [[Context Data Model 2.0]] for the version currently under development
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| − | == Introduction ==
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| − | Although it can be used for almost any kind of data, the focus of the [[Context Data Model]] is to provide a foundation for integrating, unifying, and sharing identity-related data. In particular we are focused on information about a person, a group or an entire organization. This might include contact information, authentication data, preferences, email addresses, interests, employer-related information. An object representing a single person, might have relationships to other objects and other people in the same or different data contexts.
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| − | See:
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| − | * [[Context Data Model Background]] for information about motivations and design goals.
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| − | == Core Semantics ==
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| − | The [[Context Data Model]] encompasses the core semantics of the W3C's [http://www.w3.org/RDF/ Resource Description Framework] (RDF); anything expressible in RDF is expressible in the [[Context Data Model]] although the converse isn't true.
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| − | Most of the subtle but important differences between [[Context Data Model]] and RDF are derived from differences in the choice of identifiers used to identify objects in each model. RDF is based on pure HTTP URIs, whereas [[Context Data Model]] is based on a more generalized URI called a [[UDI]]. Objects identified by URIs in RDF are called ''Resources'', whereas in [[Context Data Model]] they are identified by [[UDI]]s and are called [[Entity | Entities]].
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| − | [[Context Data Model]] includes a kind of object called a [[Context]] that has no analog in RDF. Individual [[Context]]s can be thought of as containers of portions of the overall graph of objects. [[Context]]s partition the data space into disjoint sets of objects. [[Context Provider]] plug-in implementations map sets of data resources stored in a various kinds of data stores into objects within [[Context]] boundaries in the [[Context Data Model]]
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| − | [[Context Data Model]] also differs from RDF on a syntactic (semantically lossless) level. In RDF an object may have N properties of type T each of which has a single value whereas in [[Context Data Model]] an object may only have 0..1 property of type T, and if the property exists it has 1..N values. Further, in [[Context Data Model]] these properties are called [[Attribute]]s.
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| − | == Domain Concepts ==
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| − | The [[Context Data Model 1.0]] defines these concepts:
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| − | ; Attribute: Defines a property of an Node or a Context. Has a type (URI). Has one or more values all of which MUST be unique. The value of an Attribute is an instance of AttributeValue.
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| − | ; AttributeValue: An object that hold either a literal value or a complex value. In Higgins 1.0 this instance can also hold what was called "metadata" values (e.g. creation date-time, expiration date-time).
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| − | ; Context: A set of one or more Nodes
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| − | ; ContextId: A URI that identifies a Context
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| − | ;Entity: Person, thing, juridical entity, concept, animal or anything with separate existence.
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| − | ;Node (aka ''Digital Subject''): A representation of an Entity within a given context. Nodes and Entities are not the same concept. The distinction is subtle but critical. In Higgins the same Entity is usually represented by multiple Nodes in different Contexts.
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| − | ;NodeId: A NodeId is a kind of simple-valued Attribute of an Node. Its value uniquely identifies an instance of an Node. The value of an NodeId is a single NodeId Data Range URI
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| − | ;Node Relation: A kind of Attribute of a Node. Each value of an Node Relation identifies a Node [Note: the target Nodes may be in the same or different Contexts as the source Node ]. The value(s) of an Node Relation is a Node. More precisely, the value is a NodeId Data Range URI that is dereferenced to produce a Node instance.
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| − | ;Node Correlation: A Node Correlation is a kind of Attribute of a source Node. Each value of a Node Correlation identifies a target Node. Each source-target Node pair expresses that both Nodes are representations of the same Entity
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| − | == The HOWL Ontology ==
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| − | The [[Context Data Model]] is defined in the W3C's web ontology language in a file called [[HOWL]] (higgins.owl). Due to the differences between RDF and [[Context Data Model]] mentioned above, this description is only an approximation, albeit a useful one. It enables Higgins developers to use RDF and OWL tools and technologies in the development of Higgins applications and [[Context Provider]]s without any modifications.
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| − | [[HOWL]] is an abstract (sometimes called an "upper") ontology for identity information. It is abstract in that it doesn't describe any concrete attributes such as "email address" or "first name". It also doesn't define very specialized classes of objects such as "calendar event" or "student", "movie", "book", etc. These are left to [[Context Provider]]s to define for themselves.
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| − | See also:
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| − | * [[HOWL]]
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| − | === Extending HOWL ===
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| − | Developers must create specialized ontologies based on HOWL that describe specific concrete domains.
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| − | For example, if a developer wanted to describe a CRM database, she would create an OWL ontology that would describe the data objects in the CRM database. This CRM database is called a [[Context]] in Higgins. If, for example, the database contained records about customers and those customers had full-names and email addresses, then the developer would define "Customer" as a sub-class of Node (Digital Subject) and "full-name" and "email" as kinds of attributes.
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| − | Here are some HOWL-based Ontologies:
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| − | * [[test-person Example Context Ontology]]
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| − | * [[Person-with-address Example Context Ontology]]
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| − | * [[Person-with-friend Example Context Ontology]]
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| − | [[Category:Higgins Data Model]]
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