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Application profile
Application profile consists of data elements drawn from one or more namespace schemas combined together by implementers and optimized for a particular local application. Application profiles are useful as they allow the implementer to declare how they are using standard schemas.

Crosswalk
A chart or table that represents the semantic mapping of fields or data elements in one data standard to fields or data elements in another standard that has a similar function or meaning. Crosswalks enable heterogeneous databases to be searched simultaneously with a single query as if they were a single database (semantic interoperability) and to effectively convert data from one metadata standard to another. See also metadata mapping below. Also known as Mapping.

DTD (Document Type Definition)
A formal specification of the structural elements and markup definitions to be used in encoding certain types of documents in SGML.

Geospatial data
Information that identifies the geographic location and characteristics of natural or constructed features and boundaries on the earth. This information may be derived from, among other things, remote sensing, mapping, and surveying technologies.

Harvest
A system providing software architecture for gathering, indexing and accessing Internet information with certain protocol and descriptive metadata schema.

Interoperability
The ability of two or more systems or components to exchange information and use the exchanged information without special effort on either system.

MARC
MAchine Readable Cataloguing. A family of formats based on ISO 2709 for the exchange of bibliographic and other related information in machine readable form. For example, USMARC, UKMARC and UNIMARC.

Metadata
Data about data. Metadata describes how and when and by whom a particular set of data was collected, and how the data is formatted. Metadata is essential for understanding information stored in data warehouses.

Namespace
The set of unique names used to identify objects within a well-defined domain, particularly relevant for XML applications. For example, the following element names constitute the Dublin Core Metadata Element Set namespace: DC.Creator, DC.Title.

Registry
The characteristics of an architecture for metadata that will allow independently developed metadata element sets to co-exist. It describes the semantics, the structure and the transport syntax of a metadata element set. It contains the applications of different metadata standard, their elements and semantic definitions. It may also include policies or recommended practice for use of the defined terms.

Schema
the place where definitions and restrictions of usage for properties are documented. Metadata schema provides a formal structure designed to identify the knowledge structure of a given discipline and to link that structure to the information of the discipline through the creation of an information system that will assist the identification, discovery and use of information within that discipline.

Uniform Resource Identifier (URI)
It is a compact string of characters for identifying an abstract or physical resource. It can be further classified as a locator, a name, or both.

Uniform Resource Locator (URL)
R refers to the subset of URI that identify resources via a representation of their primary access mechanism (e.g., their network "location"), rather than identifying the resource by name or by some other attribute(s) of that resource.

Uniform Resource Name (URN)
R refers to the subset of URI that are required to remain globally unique and persistent even when the resource ceases to exist or becomes unavailable.

XML (Extensible Markup Language)
A data format for structured document interchange that is more flexible than HTML. While HTML's tags are predefined, XML allows tags to be defined by the developer of the page. Thus, XML-defined Web pages can function like database records.

Z39.50 (ISO 23950 / ANSI Z39.50)
A NISO standard for an applications layer protocol for information retrieval, which is specifically designed to aid retrieval from distributed servers, a client/server-based protocol for searching and retrieving information from remote databases. It defines a standard way for two computers to communicate for the purpose of information retrieval, separates the user interface on the client side from the information servers, search engines, and databases.

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