Each XML document has both a physical and a logical structure. Physically, the document is composed of units called entities. An entity may refer to other entities to cause their inclusion in the document. A document begins in a "root" or document entity and is structured with objects, attributes and relationships. Logically, the document is composed of declarations, elements, comments, character references, and processing instructions, all of which are indicated in the document by explicit markup.
The XML DTD contains markup declarations that provide a grammar for the XML documents.
Each XML document contains one or more elements, the boundaries of which are delimited by open and close tags. Each element has a type (object, attribute, or relationship) and may have a set of attribute specifications. Each attribute specification has a name and a value.
Chapter 2, ICIM XML Elements, contains detailed information on the structure of the ICIM/XML document.