Table of contents

Appendices

2 Location Paths

Although location paths are not the most general grammatical construct in the language (a [LocationPath] is a special case of an [Expr] ), they are the most important construct and will therefore be described first.

Every location path can be expressed using a straightforward but rather verbose syntax. There are also a number of syntactic abbreviations that allow common cases to be expressed concisely. This section will explain the semantics of location paths using the unabbreviated syntax. The abbreviated syntax will then be explained by showing how it expands into the unabbreviated syntax (see Abbreviated Syntax).

Here are some examples of location paths using the unabbreviated syntax:

• child::para selects the para element children of the context node

• child::* selects all element children of the context node

• child::text() selects all text node children of the context node

• child::node() selects all the children of the context node, whatever their node type

• attribute::name selects the name attribute of the context node

• attribute::* selects all the attributes of the context node

• descendant::para selects the para element descendants of the context node

• ancestor::div selects all div ancestors of the context node

• ancestor-or-self::div selects the div ancestors of the context node and, if the context node is a div element, the context node as well

• descendant-or-self::para selects the para element descendants of the context node and, if the context node is a para element, the context node as well

• self::para selects the context node if it is a para element, and otherwise selects nothing

• child::chapter/descendant::para selects the para element descendants of the chapter element children of the context node

• child::*/child::para selects all para grandchildren of the context node

• / selects the document root (which is always the parent of the document element)

• /descendant::para selects all the para elements in the same document as the context node

• /descendant::olist/child::item selects all the item elements that have an olist parent and that are in the same document as the context node

• child::para[position()=1] selects the first para child of the context node

• child::para[position()=last()] selects the last para child of the context node

• child::para[position()=last()-1] selects the last but one para child of the context node

• child::para[position()>1] selects all the para children of the context node other than the first para child of the context node

• following-sibling::chapter[position()=1] selects the next chapter sibling of the context node

• preceding-sibling::chapter[position()=1] selects the previous chapter sibling of the context node

• /descendant::figure[position()=42] selects the forty-second figure element in the document

• /child::doc/child::chapter[position()=5]/child::section[position()=2] selects the second section of the fifth chapter of the doc document element

• child::para[attribute::type="warning"] selects all para children of the context node that have a type attribute with value warning

• child::para[attribute::type='warning'][position()=5] selects the fifth para child of the context node that has a type attribute with value warning

• child::para[position()=5][attribute::type="warning"] selects the fifth para child of the context node if that child has a type attribute with value warning

• child::chapter[child::title='Introduction'] selects the chapter children of the context node that have one or more title children with [string-value] equal to Introduction

• child::chapter[child::title] selects the chapter children of the context node that have one or more title children

• child::*[self::chapter or self::appendix] selects the chapter and appendix children of the context node

• child::*[self::chapter or self::appendix][position()=last()] selects the last chapter or appendix child of the context node

There are two kinds of location path: relative location paths and absolute location paths.

A relative location path consists of a sequence of one or more location steps separated by /. The steps in a relative location path are composed together from left to right. Each step in turn selects a set of nodes relative to a context node. An initial sequence of steps is composed together with a following step as follows. The initial sequence of steps selects a set of nodes relative to a context node. Each node in that set is used as a context node for the following step. The sets of nodes identified by that step are unioned together. The set of nodes identified by the composition of the steps is this union. For example, child::div/child::para selects the para element children of the div element children of the context node, or, in other words, the para element grandchildren that have div parents.

An absolute location path consists of / optionally followed by a relative location path. A / by itself selects the root node of the document containing the context node. If it is followed by a relative location path, then the location path selects the set of nodes that would be selected by the relative location path relative to the root node of the document containing the context node.