Elements of DTD

An element is the basic building block of an XML document. XHTML tags are all elements: , ,
, etc. There are three primary types of elements:

1. simple elements
   These are elements that contain text or "parsed character data" (represented as #PCDATA in your DTD). In XHTML, the tag is an example of a simple element.
2. compound elements
   These elements contain other elements, and sometimes PCDATA and other elements. In XHTML, the tag is an example of a compound element.
3. standalone elements
   These elements are often called "singleton" tags. They do not contain any PCDATA or other elements. In XHTML,
   is an example of a standalone element.