uses several techniques from XML Schema to allow as-needed element substitutions for pre-existing NIEM properties and into pre-existing NIEM types. Element substitution techniques allow the substitution of new XML Schema elements, representing derived NIEM properties that can be used where the parent properties are expected. There are three XML Schema techniques that support the NIEM use of element substitutions: use of substitution groups creation of abstract, type-less elements, and use of abstract elements in reference schemas. Adapting external standards In addition to adding new NIEM types and properties to NIEM, it is possible to adapt existing external (non-NIEM) namespaces for use in the NIEM framework. This allows the use of external standards within NIEM IEPDs, without requiring that the external standards themselves be NIEM-conformant. The intent here is to allow use of external standard components exactly as they were defined. Metadata Metadata, or data about data, defines information that supports the actual content of XML instances. The metadata feature provides a mechanism for attaching structured properties that describe the pedigree or source (when reported, who reported, how reliable, etc.) of instance data to any data component of the model (type or object, property, association, role, or augmentation) in any namespace. It allows sets of metadata to be extended with additional properties for local requirements and enables metadata properties to be repeated. EIEM dictionary concepts NIEM has introduced the concept of Enterprise Information Exchange Model (EIEM) dictionaries to allow NIEM implementers to position local collections of components specific to their own enterprise. Typically these may be drawn from an Enterprise Data Model (EDM) and then exported and refactored as XML components that conform to the NIEM NDR. See Tools section below for information on creating EIEM dictionaries. Tools NIEM provides a reference set of tools freely available with each NIEM release. The tools implement all of the structural and content features of the release, including the NIEM NDR. NIEM's well-defined interfaces and output products also support the development of independent third-party tools. Example supporting third-party tools are listed below. NIEM XML data dictionary spreadsheet The NIEM XML data dictionary spreadsheet is a tangible representation of the entire NIEM data dictionary. It includes all of the element names that are organized hierarchically under core data components (person, property, organization, etc.) with hyperlinks to related elements. This spreadsheet also provides information on the type of data being represented (date, integer, string, etc.) and