A special object that configures the environment of the document. It may introduce a new element, create an entity, or name the type of document. Declarations use a special delimiter to keep them apart from elements, adding an exclamation mark to the opening angle bracket:

<!name statement>

where name is the type of declaration, and statement contains the rest of the required information to make a declaration. See also markup.


Any character or group of characters that separates data or markup. The angle brackets in XML tags (< >) are delimiters. CDATA sections have three delimiters: <![, [, and ]]>. See also markup.


In XML, a document is a complete root element, after all external entity references have been resolved. At most, it has one optional XML declaration and one document type definition. The document may be distributed across many files, perhaps on different systems. See also document element, root element.

document element

Also called the root element, the document element is the outermost element in a document. It contains everything except the document prolog and any comments or processing instructions outside of it. See also document, root element.

document instance

An actual document that conforms to a general document model. See also document, DTD.

document model

A template for a document that defines elements and their content models. A DTD or a schema is a document model. See also DTD, schema.

DOM (document object model)

A specification that defines the structure of a document as a collection of objects and how the document can be accessed and manipulated. A document object model is an API (application programming interface), which describes how programs actually interpret the structure and contents of a document.

document prolog

A section at the beginning of a document that declares the document to be XML, and specifies the version of XML it conforms to (for example, <?xml version="1.0"?>). Additional information about the document can be declared, including the document type declaration. The document prolog precedes the document element or root element, which contains all the content of the document. See also document, document type declaration, XML declaration.

document tree

Every XML document can be represented in a special structural form called a tree. It's tree-like because it originates from one point (the root) and branches out into leaves. Each point in the tree where a branching occurs is called a node. A tree consists of a root node, many branch nodes, and a smattering of leaf nodes. Strangely, most document trees are drawn upside-down, with the root on top.

Document trees can be divided into smaller trees, in that any node can be considered the root of its own subtree. This fact is important in understanding XML transformations using XSLT, which effectively chops a tree into smaller and smaller subtrees, then assembles a result tree in reverse fashion. See also document, node tree.

document type declaration

The DOCTYPE section of the document prolog. This section declares the structure to which the document must conform. It can be used to specify a DTD by providing its public identifier and location by URI. It can also specify an internal subset of entity declarations used in the document. See also document, DTD.

DOM (Document Object Model)

A tree-based interface for accessing and manipulating the contents of XML documents.

DTD (document type definition)

A set of declarations that defines the names of the elements and their attributes and specifies rules for their combination and sequence. See also document, document type declaration.