Entity

{{#eclipseproject:technology.higgins}}

Version

This page describes the Higgins concept of Entity used in the Context Data Model 1.1.

Introduction

It is similar to the Identity Gang Lexicon's definition of Digital Subject but must not be confused with the Gang's definition of Entity.

An Entity is a representation of an person, group, thing or concept within a given context. In Higgins the same person, group, etc. is often represented by multiple Entities in different Contexts.

Definition

• A digital representation of a person, group, thing or concept within a given context. Entity Class objects and Attribute Definitions are also represented as Entities.
• An Entity has zero or more Attributes
• Almost all Entities have a single EntityId that uniquely identifies the Entity within its containing Context.

Details

• Some of the Attributes of an Entity may be references to other Entities in the same or different Contexts. These are called Entity Relations. For example, an Entity representing Bob may have a "knows" Entity Relation Attribute pointing to an Entity representing Bob's friend Alice.
• A single person (thing or concept) may be represented as one (or more) Entities in one Context and (an)other Entities in other Contexts. By linking or "federating" these disparate Entities one can gain a more unified view of a given person. Contexts representing different systems, organizations and entire enterprises with widely varying storage and trust models are handled using this Entity linking approach. For example the person Bob Smith could be represented as two Entities in the same or in different Contexts interconnected by a Entity Correlation Attribute
• Contexts can be nested (e.g. enterprises have sub-organizations, and there are systems within an enterprise/org, etc.) or related through other means (employment/HR system vs. customer system where same person is a customer and an employee). Thus linking the Entities relevant to those contexts provides an a broader view of a Entity.
• The information contained in one Entity is not necessarily a pure subset of the union of all of the information contained in all of the linked Entities representing a person taken together. There is no consistency constraint imposed between the Entities of an person. For example, a person could be represented such that their name was Joe in one Entity in one Context and JoAnn in another Entity in another Context.

Entity Classes

Each Context has an associated ontology/schema. This schema must import and build on the terms in higgins.owl 1.1. Within this ontology the Context can define its own Entity Classes and Attribute Definitions. When defining a Entity class, the class definition can place restrictions on the cardinality of Attribute types also defined in the ontology. A given Entity subclass:

• MAY define the minimum cardinality of an Attribute type, that is, the minimum number of values allowed (e.g. >=3 values)
• MAY define the maximum cardinality of an Attribute type, that is, the maximum number of values allowed (e.g. <=100 values)