DTD element

In a DTD, element by element declaration to be declared.

Declare an element

In a DTD, XML element by element declaration to be declared. Element declaration with the following syntax:

Empty elements

Empty elements declared by category keyword EMPTY:

Only PCDATA element

Only PCDATA elements inside parentheses #PCDATA declared:

Elements with no content

Statement by category keyword ANY element can contain any combination of parsable data:

Element has children (sequence)

Elements with one or more children elements inside parentheses child element names declared:

When the sub-elements separated by commas according to the sequence of statements, these sub-elements must appear in the same order in the document. In a full declaration, the children must also be declared, but also child elements can have child elements. "Note" element is the complete statement:

Statement elements appear only once

The above example declares: message the child elements must appear once, and must appear only once in the "note" element.

Declaration element appears at least once

The example above the plus sign (+) declares: message the child elements must appear at least once in the "note" element.

Zero or more element declarations appear

The above examples asterisk (*) declares: child element message can appear in the "note" element zero or more times.

Declaring zero or one element

The above example declares question mark (?): The child element message can appear in the "note" element zero or one time.

Statement "Non ... / ... both" types of content

The above example declares: "note" element must contain a "to" element, "from" element, "header" element, as well as non "message" element only "body" element.

Content declaration hybrid

The above example declares: "note" element can contain zero or more times PCDATA, "to", "from", "header" or "message".