IEPD Conformance

An Overview

What is NIEM?

NIEM is the National Information Exchange Model, a collaborative project to aid information exchange across a broad community, to ensure that data in motion works with a broad array of tools, and retains its meaning across organzational boundaries. The NIEM community brings together state, local, tribal, and federal government organizations within the United States, along with international partners, to define reusable data structures and rules for their use.

NIEM has two technical aspects that work together:

1. The NIEM model, a set of data components that have been collaborative developed and refined over time. These data components are reusable, extensible data types and relationships, which cover a broad set of data needs across the community.
2. A set of practices for defining and reusing the components, so that messages and their specifications have clear meaning, and that they reuse and extend the NIEM data components in an understandable way.

The NIEM community consists of groups that govern the technical architecture and the data model of NIEM. Data model governance is distributed, with a core group governing the NIEM core, and self-governing domains addressing functional areas, like justice, agriculture, and transportation.

What is NIEM conformance?

NIEM has developed a set of practices for information exchanges, which include:

1. Reuse the NIEM data components, when appropriate.
2. Otherwise, extend and specialize the NIEM data components as needed.
3. Construct new data components to express any concepts specific to an exchange or community, when the NIEM model doesn’t cover a concept.
4. Use NIEM methods for common data modeling needs. For example, NIEM describes:
   • references, which create links between data items,
   • associations, which express complex relationships that carry their own data,
   • augmentations, which add characterstics to already-defined classes of objects
   • external types, which carry non-NIEM data in a NIEM message, and
   • roles, which express a role or function of an entity.
5. Make the specifications for exchanges precise, so that software can support the use and comprehension of messages, as well as ensuring that messages obey the rules of their specifications.
6. Construct messages so that software can ensure that they follow their specifications, and reuse NIEM terms (namespaces and local names), so that the identity and expected content ofmessages are consistent and unambiguous.

The National Information Exchange Model has developed a set of rules for various pieces that make up an information exchange. Something that follows these rules is called NIEM-conformant.

What does NIEM conformance accomplish?

The Value of NIEM page describes the results of using NIEM, which include:

• Quicker, cheaper development of information exchanges
• Broad usability of exchanges across architectures and platforms
• Consistent understanding of messages between senders and receivers, and across wider communities
• Broad software support of technical features of messages
• The ability to reuse a message format over long periods of time

What can be NIEM-conformant?

There are several pieces that make up information exchange. NIEM has rules for each of these, to support understanding of messages and to convey meaning:

1. An IEP (information exchange package): an XML document that constitutes a message, exchange, data item, or payload. An IEP may be transmitted from a sender to a receiver, or may be a static document.

2. An IEPD (information exchange package description): An IEP or message is defined by an specification; NIEM calls this specification an IEPD. An IEPD is defined by a community to describe a set of messages. An IEPD contains an XML Schema, documentation, and other needed files.

3. An XML schema: An IEP is described by an XML schema, which is a set of XML Schema documents that together describe the XML format of a message.

4. An XML Schema document: An XML Schema document (XSD) is an XML document that describes some features of XML documents. A set of XSDs are brought together to form an XML schema, which is used by an XML Schema-validating parser to make data accessible to software.

NIEM has practices that each of these pieces must follow in order to be conformant.

How do I make something NIEM-conformant?

NIEM has practices, methods, and formats for the pieces that compose an information exchange. These are expressed as a set of specifications. These specifications can be useful to an individual developer or implementer of an exchange, however we don’t expect most developers to read them.

We encourage developers to use tools provided by the NIEM program to construct and validate a NIEM-conformant exchange, including:

• Use the NIEM Schema Subset Generation Tool to find and assemble NIEM data components into an XML Schema subset.
• Use an XML Schema development environment or editor to construct extension schemas to express additional concepts needed for an exchange.
• Assemble schemas and other documents into an IEPD using the NIEM IEPD Tool.
• Ensure IEPDs and schemas follow the NIEM rules using the NIEM Conformance Testing Assistant (Contesa)
• Build messages that validate against the XML Schemas, and which use advanced language features as described by the NIEM Naming and Design Rules section 12, which describes the meaning of NIEM XML data and references between data objects.

Additional details

In addition to the tools above, developers may use the specifications to guide development of conformant artifacts. Relevant specifications include:

• The NIEM Naming and Design Rules, which provides rules for XML Schemas and documents.
• The NIEM Code Lists Specification, which supports the NDR with additional methods for describing and using code lists, as CSV spreadsheets, Genericode XML, or via services.
• The NIEM Model Package Description Specification, which provides rules for syntax and interpretation of NIEM IEPDs.
• The NIEM Conformance Specification, which provides additional details and references for conformance of artifacts.