XML Glossary

attribute: XML structural construct. A name-value pair within a tagged element that modifies certain features of the element. For XML, all values must be enclosed in quotation marks.
CDATA section: XML structural construct. CDATA sections can be used to mark tags or reserved characters with quotation marks and thus prevent them from being interpreted. For this reason, the CDATA section is especially useful for escaping markup and script. The syntax for CDATA sections in XML is <![CDATA[ ... ]]>.
character data: XML structural construct. The text content of an element or attribute.
character set: A mapping of a set of characters to their numeric values. For example, Unicode is a 16-bit character set capable of encoding all known characters; it is used as a worldwide character-encoding standard.
component: An object that encapsulates both data and code, and provides a well-specified set of publicly available services.
data binding: The process of associating the objects or controls of an application to a data source. A control associated with a data source is called a databound control. Data binding can be used to move XML-based data elements into HTML for display, essentially merging data into an HTML presentation template. The contents of a databound control are associated with values from a database. For example, a grid control that is bound to a Recordset object can be updated when the rows in the Recordset are updated. When new values are retrieved by the Recordset, new values are displayed in the grid.
data island: A proposed format for putting XML-based data inside HTML pages (<XML> or <SCRIPT language="XML">). HTML is used as the primary document or display format, and XML is used to embed data within the document.
data type: The type of content that an element contains: a number, a date, and so on. In XML, an author can specify an element's data type, for example, with a tokenized attribute type. Microsoft is working with the W3C to define a set of standard types that anyone can freely use.
document element: The top-level element of an XML document; only one top-level element is allowed. The document element is a child of the document root.
document root: The top-level node of an XML document; its descendants branch out from it to form the XML tree for that document. The document root contains the document element and can also contain a set of processing instructions and comments.
document type declaration: XML structural construct. A production within an XML document that contains or points to markup declarations that provide a grammar for a class of documents. This grammar is known as a Document Type Definition. The document type declaration can point to an external subset (a special kind of external entity) containing markup declarations, or can contain the markup declarations directly in an internal subset, or both. The DTD for a document consists of both subsets taken together. The syntax of the document type declaration is <!DOCTYPE content >.
element: XML structural construct. An XML element consists of a start tag, and end tag, and the information between the tags, which is often referred to as the contents. Elements used in an XML file are described by a DTD or schema, either of which can provide a description of the structure of the data.
entity: XML structural construct. A character sequence or well-formed XML hierarchy associated with a name. The entity can be referred to by an entity reference to insert the entity's contents into the tree at that point. The function of an XML entity is similar to that of a macro definition. Entity declarations occur in the DTD.
entity reference: XML structural construct. Refers to the content of a named entity. The name is delimited by the ampersand and semicolon characters; for example, &bookname; and <. It is used in much the same way as a macro.
event handler: The code that is executed when an event occurs.; .
granular updating: Changing only an element of a page, rather than rebuilding the entire page. The new element is sent from the server to the client, which replaces the old element while leaving the rest of the page intact.
graphing: A very generalized way to represent certain data relationships.
ID: A special attribute type within the XML language. The ID attribute on the XML element provides a unique name, enabling links to that element using the IDREF attribute type. The value associated with the ID attribute must be unique within that XML document. IDs are currently declared with a DTD or schema.
markup: XML structural construct. Text in an XML document that does not represent character data: start tags, end tags, empty-element tags, entity references, character references, comments, CDATA section delimiters, DTDs, and processing instructions.
mixed content: XML structural construct. An element type has mixed content when elements of that type can contain character data, optionally interspersed with child elements. In this case, the types of the child elements can be constrained, but not their order or their number of occurrences.
namespace: A mechanism to resolve naming conflicts between elements in an XML document when each comes from a different vocabulary; it allows the commingling of like tag names from different namespaces. A namespace identifies an XML vocabulary defined within a URN. An attribute on an element, attribute, or entity reference associates a short name with the URN that defines the namespace; that short name is then used as a prefix to the element, attribute, or entity reference name to uniquely identify the namespace. Namespace references have scope. All child nodes beneath the node that specifies the namespace inherit that namespace. This allows nonqualified names to use the default namespace. See also RDF namespace.
NDATA: The literal string "NDATA" is used as part of a notation declaration.
normalize: To collapse two or more adjacent text nodes in the document tree into one text node. This ensures that the tree structure will match tree structure generated when the document is stored and reloaded. The element object offers a normalize method.
notation: Usually refers to a data format, such as BMP. A notation identifies by name the format of unparsed entities, the format of elements that bear a notation attribute, or the application to which a processing instruction is addressed.
notation declaration: A notation declaration provides a name and an external identifier for a notation. The name is used in entity and attribute-list declarations and in attribute specifications. The external identifier is used for the notation, which can allow an XML processor or its client application to locate a helper application capable of processing data in the given notation.

processing instruction (PI): XML structural construct. Instructions that are passed through to the application. The target is specified as part of the PI. The syntax for a PI is <?pi-name content?>.; .
reference node: The reference node for a search context is the node that is the immediate parent of all nodes in the search context. Every search context has an associated reference node.
root element: Sometimes this term is used to refer to the document element but this is misleading, since the top-level element and the document root are not the same. Because of this ambiguity, use of the term "root element" is discouraged.
schema: A formal specification of element names that indicates which elements are allowed in an XML document, and in which combinations. A schema is functionally equivalent to a DTD, but is written in XML; a schema also provides for extended functionality such as data typing, inheritance, and presentation rules.
target: The application to which a processing instruction is directed. The target names beginning with "XML" and "xml" are reserved. The target appears as the first token in the PI. For example, in the XML declaration <?xml version="1.0"?>, the target is "xml".
text markup: Inserting tags into the middle of an element's text flow, to mark certain parts of the element with additional meta-information.
tokenized attribute type: Each attribute has an attribute type. Seven attribute types are characterized as tokenized: ID, IDREF, IDREFS, ENTITY, ENTITIES, NMTOKEN, and NMTOKENS.
updategram: XML generated by agents to notify the client of changes to data on the server, or vice versa; the agents could run on the middle tier to access multiple existing database management systems (DBMSs) and output XML.