1. Home
  2. Reference
  3. Model Concepts

Model Concepts

Learn about properties, types, augmentations, and other building blocks used to construct the model.

Click here for a one-page summary of each of the major concepts.

The concepts below have NIEM-specific representations in XML and JSON. Each section has pages that demonstrate how to define these concepts in a schema and how sample data would appear in an instance. For a basic introduction to XML or JSON, there are many resources available online, including W3 Schools XML Tutorial and XML Schema Tutorial, and the Space Telescope Science Institute Understanding JSON Schema.

The Basics

Fundamentally, a NIEM release consists of a set of namespaces, each of which define properties and types (referred to more generally as components). An IEPD reuses components from a release that meet its requirements, and creates new properties and types in local namespaces as needed. These namespaces, properties, and types are basic building blocks of NIEM.

  • Namespaces
    A namespace is a collection of properties and types, managed by a common authoritative source.
  • Properties
    A property represents a concept, idea, or thing.
  • Types
    A type represents a data structure that defines a set of allowable values.
  • Codes / Facets
    A facet is a constraint on a simple type that limits the set of allowable values.

Advanced

In addition to the basic concepts described above, NIEM defines or uses additional concepts to reflect its conceptual model, improve reusability, and support well-defined information exchanges.

  • Adapters
    An adapter is a mechanism to use components from a non-conformant external standard within a NIEM-conformant namespace.
  • Associations
    An association is a complex relationship between objects, with optional additional characteristics.
  • Augmentations
    An augmentation is a mechanism to add additional local content to NIEM types defined in other namespaces.
  • Local Terminology
    Local terminology is a word, phrase, abbreviation, acronym, jargon, or other string of characters specially documented in a namespace because no definition or literal exists in a standard dictionary.
  • Metadata
    Metadata is a set of data that describes characteristics of other data.
  • References
    A reference is used to link to content defined elsewhere.
  • Representation Pattern
    The representation pattern is a mechanism to support multiple representations of a concept, along with additional properties.
  • Roles
    A role is a function or responsibility of someone or something.