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DATA MODEL (XPATH)

The data model is a description of the kinds of objects that can be manipulated by XPath expressions, and their properties and relationships. Examples of such objects are sequences, items, atomic values, nodes, and trees. (Sometimes the term data model is used loosely to refer to a specific object, such as the tree representation of a particular document).

DECLARATION ( XSLT )

A declaration is a top-level element in a stylesheet module (that is, a child element of the <xsl:stylesheet> element), other than a user -defined data element, which is ignored by the XSLT processor.

DEFAULT NAMESPACE DECLARATION ( XML )

This takes the form of an XML attribute xmlns="uri" . It declares that within its scope, an element name with no explicit prefix will be associated with a particular namespace URI. The default namespace is used only for element names ; other objects with no prefix (for example, attributes) have a null namespace URI.

DESCENDANT AXIS ( XPATH )

The descendant axis selects all the children of the context node, their children, and so on, in document order. This is a forwards axis.

DESCENDANT-OR-SELF AXIS (XPATH)

The descendant-or-self axis selects the context node followed by all the nodes on the descendant axis. This is a forwards axis.

DOCUMENT ( XML )

A parsed entity that conforms to the XML syntax for a Document is said to be a well- formed document; a document that also obeys the rules in its document type definition is said to be valid. In XSLT and XPath the term document is often used to refer to the tree representation of a document: that is, a document node together with all the nodes that have this document node as an ancestor .

DOCUMENT ELEMENT ( XML )

The outermost element of a document, the one that contains all other elements. The XML standard also refers to this as the root element, but it must not be confused with the root node in the XPath tree model: the root node is usually the document node that is the parent of the document element, which represents the document itself.

DOCUMENT NODE (XPATH)

If the tree represents a well-formed XML document, the root node will be a document node with exactly one element node as a child, representing the document element, and no text nodes as children. In other cases it may have zero or more element node children, and zero or more text node children: I refer to such a document as being well-balanced. In both cases the root node may also have comment nodes and processing instruction nodes as children.

DOCUMENT ORDER (XPATH)

The nodes in a sequence can always be sorted into document order. For elements from the same document, document order is the same as the order of the start tags in the original source. In terms of the tree structure, a node is ordered after its preceding siblings, and these are ordered after their parent node. The ordering of attribute and namespace nodes, and of nodes from different source documents, is only partially defined.

DOCUMENT TYPE DEFINITION (DTD) (XML)

The definition of the structure of an XML document, or a collection of XML documents. May be split into an external subset, held in a separate file, and an internal subset, embedded within the document itself.

DYNAMIC CONTEXT (XPATH)

The dynamic context of an XPath expression is the total collection of information available to the XPath engine at evaluation time. This includes the context item, context position, and context size , the values of all variables , and the contents of all documents that can be accessed by their URI, using functions such as doc() and document() .

DYNAMIC ERROR (XPATH)

A dynamic error is an error detected during the evaluation phase, as distinct from a static error, which is detected at compile time. Technically, type errors (which may be detected either at compile time or at runtime) form a separate third category.

Dynamic errors defined in XSLT are classified as being either recoverable or nonrecoverable. In the case of recoverable errors the processor is allowed either to report the error, or to recover in a defined way and continue processing, or both.

EFFECTIVE BOOLEAN VALUE (XPATH)

The effective boolean value of an expression is used when the expression appears in a context where a choice needs to be made: for example the condition in an XPath conditional expression or an XSLT <xsl:if> instruction. The effective boolean value of a sequence is false if the sequence is empty, or if it contains a singleton atomic value that is the boolean false , a zero-length string, a number equal to zero, or NaN ; in all other cases, the effective boolean value is true .

EFFECTIVE VALUE (XSLT)

The effective value of an attribute in an XSLT stylesheet is the value after expanding any attribute value template: for example given the instruction <xsl:message terminate="{$term}"/> , the effective value of the «terminate » attribute is the value of the $term variable.

ELEMENT (XML)

A logical unit within an XML document, delimited by start and end tags, for example <publisher>Wrox Press</publisher> ; an empty element may also be written in abbreviated form, for example <publisher name="Wrox"/> .

ELEMENT DECLARATION (SCHEMA)

An element declaration is a schema component that corresponds to an <xs:element> element in a schema: it defines the structure of elements having a particular name. It may be a global element declaration (if it is defined at the top level of a schema) or a local element declaration (if defined within the structure of a complex type ).

ELEMENT NODE (XPATH)

A node in a tree that represents an element in an XML document. The parent of the element node is either the containing element or the document node of the tree; its children are the element nodes, text nodes, comment nodes, and processing instruction nodes derived from the immediate content of the XML element.

EMBEDDED STYLESHEET MODULE (XSLT)

A stylesheet module that does not constitute an entire XML document in its own right, but is embedded as an <xsl:stylesheet> element within some larger XML (or perhaps non-XML) document.

EMPTY SEQUENCE (XPATH)

An empty sequence is a sequence containing no items.

ENTITY REFERENCE (XML)

A reference to an internal or external entity, generally in the form «&name; » . Note that numeric references of the form «&#x20; » are correctly referred to as character references rather than entity references.

ENTITY ( XML )

A physical unit of information that may be referenced within an XML document. Internal entities are embedded within the document in its Document Type Definition; external entities are generally held as a separate file. A parsed entity contains text with XML markup; an unparsed entity contains binary data. A general entity contains material for inclusion in the document; a parameter entity contains material for inclusion in the Document Type Definition.

EXPANDED QNAME (XPATH)

The term QName is sometimes used to mean a QName as written in source XML documents, that is a construct of the form «prefix:local-name » , and it is sometimes used to mean the (namespace-uri, local-name) pair that this represents. Within the XSLT 2.0 and XPath 2.0 specifications the preferred usage is lexical QName for the first construct, and expanded QName for the second. These terms are not consistent across the full range of XML specifications.

There is no standard convention for displaying an expanded QName, though in some interfaces such as JAXP, expanded QNames are written in the form «{namespace-uri}local-name » . This is sometimes referred to as Clark notation.

EXPRESSION ( XPATH )

An XPath construct that can be evaluated to yield a value, which will always be a sequence (of nodes and/or atomic values ). In XSLT, expressions are used in many contexts such as the select attribute of <xsl:for-each> , <xsl:value-of> , and <xsl:variable> , and the test attribute of <xsl:if> and <xsl:when> . Expressions are also used between curly braces in attribute value templates.

EXTENSION ATTRIBUTE ( XSLT )

An attribute in a vendor- or user-defined namespace used on an XSLT element in the stylesheet. Such attributes may be used to control behavior that would otherwise be implementation defined, or to provide extra control over serialization.

EXTENSION INSTRUCTION ( XSLT )

An element within a sequence constructor that is defined by a product vendor, a user, or a third party, but otherwise behaves like an XSLT instruction. The XSLT specification defines how extension instructions are evaluated but not how they are implemented. In XSLT 1.0, extension instructions were referred to as extension elements.

EXTENSION FUNCTION (XSLT)

A function defined by a product vendor, a user, or a third party, which can be called from within an XPath expression. The XSLT specification defines how extension functions are called but not how they are implemented.