A pointer, verbal or graphical or both, to a component of an illustration or a text object. The processor is not expected to rearrange, select, or suppress any of the elements, but simply present them as specified. A set of declarations that defines the names of the elements and their attributes, and that specifies rules for their combination or sequence. Elements define the hierarchical structure of a document. Most elements have start and end tags and contain some part of the document content.
Empty elements have only a start tag and have no content.
For example, in DocBook, Footnote excludes Footnote . This means that footnotes cannot nest, even though Footnote contains Para , and Footnote occurs in the proper content model of Para . See Section 1.4.2.1 . An external entity is a general entity that refers to another document. External entities are often used to incorporate parsable text documents, like legal notices or chapters, into larger units, like chapters or books.