unparsedEntityDecl

unparsedEntityDecl is an event generated by an XML or SGML parser when it encounters an unparsed entity declaration in the document's DTD. An unparsed entity is a resource, such as an image or a binary file, that the parser does not process as XML or SGML markup. Instead, the parser makes the entity's location and type available to the application, which can then fetch and process it independently.

When a parser encounters an unparsed entity declaration, it typically invokes a callback function or triggers an event. This event, often referred to as unparsedEntityDecl, passes information about the entity to the application. This information usually includes the entity's name, its system identifier (typically a URI), and its public identifier (if provided). Crucially, it also includes the notation name, which specifies the format of the unparsed entity. The notation itself must be declared elsewhere in the DTD.

Applications use the unparsedEntityDecl event to manage external resources referenced within an XML or SGML document. For example, a web browser might use this information to display an image declared as an unparsed entity. A data processing application might use it to retrieve a binary file for further analysis. The parser's role is to inform the application of the existence and characteristics of these external resources, allowing the application to handle them appropriately.