a special declaration that identifies the format of non-text external data so that the XML application will know how handle the data

When content is not made up of standard data characters, the use of notations allows documents to incorporate or reference non-SGML data (such as graphics, video, sound, or small software applications).

An XML structure that identifies the type of content contains by an element and suggesting a viewer to present it.

A representation for data (TIFF, TeX, EPS, etc.) declared in an SGML DTD. Entities within an SGML document may then refer to such a notation so that an SGML processor can direct the entity to the appropriate application for processing.

In XML, the definition of a content type that is not part of those understood by the parser. These types include audio, video, and other multimedia.

A mechanism for defining a data format for a non-XML document referenced as an unparsed entity. This is a holdover from SGML that creaks a bit. The newer standard is to use MIME datatypes and namespaces to prevent naming conflicts.

The attribute value is a reference to a notation name declared in the document, indicating the data content notation of the current element.

Notation is the textual representation of model fragments on a diagram. ArgoUML supports Notation in different languages such as UML and Java. Notation may be not only pure text: e.g. UML attributes/operations have graphical text properties (underlining, italics) with a semantic relevance. To be shown on a diagram, the text has to be created by a generator, and when the user edits the text on the diagram, a parser processes the text, and adapts the model accordingly.

Tells the parser what type of object is being referenced. Usually refers to a data format of non-XML data, such as BMP. A notation identifies by name the format of unparsed entities, the format of elements that bear a notation attribute, or the application to which a processing instruction is addressed.

Identifies by name the format either of an unparsed entity or an element bearing a specific notation attribute; it can also identify the target of a processing instruction. A notation declaration gives a name to the notation and an external identifier that enables a parser or its client to locate a helper application that can process the data specificed by the notation. Notations occur in attribute values, attribute-list declarations, and entity declarations.