Table of contents

Appendices

3 Logical Structures

Each XML Document contains one or more elements, the boundaries of which are either delimited by Start-Tag and End Tag, or, for Empty elements, by an empty-element tag. Each element has a type, identified by name, sometimes called its "generic identifier" (GI), and MAY have a set of attribute specifications. Each attribute specification has a Attribute Name and a Attribute Value.

This specification does not constrain the semantics, use, or (beyond syntax) names of the element types and attributes, except that names beginning with a match to (('X'|'x')('M'|'m')('L'|'l')) are reserved for standardization in this or future versions of this specification.

Well Formedness Constraint: Element Type Match

The Name in an element's end-tag MUST match the element type in the start-tag.

Validity Constraint: Element Valid

An element is valid if there is a declaration matching elementdecl where the Name matches the element type, and one of the following holds:

1. The declaration matches EMPTY and the element has no Content (not even entity references, comments, PIs or white space).

2. The declaration matches children and the sequence of Parent/Child belongs to the language generated by the regular expression in the content model, with optional white space, comments and PIs (i.e. markup matching production [27] Misc) between the start-tag and the first child element, between child elements, or between the last child element and the end-tag. Note that a CDATA section containing only white space or a reference to an entity whose replacement text is character references expanding to white space do not match the nonterminal S, and hence cannot appear in these positions; however, a reference to an internal entity with a literal value consisting of character references expanding to white space does match S, since its replacement text is the white space resulting from expansion of the character references.

3. The declaration matches Mixed and the content (after replacing any entity references with their replacement text) consists of Character Data, Comment, Processing instruction and Parent/Child whose types match names in the content model.

4. The declaration matches ANY, and the content (after replacing any entity references with their replacement text) consists of character data and Parent/Child whose types have been declared.