Chapter 3 Building XML Models
An XPath expression allows you to locate a node (an element with its ramifications) in the hierarchical tree structure of an XML document.
The XPath expressions permitted to define constraint selectors and fields are limited to a subset of the full XPath language defined in the W3C Recommendation XML Path Language 1.0:
| Syntax | Description |
|---|---|
| / | Root node of the XML document. It is the root element with its ramifications |
| . | Selects the context node. It is the current element (on which an identity constraint is defined) with its ramifications |
| .. | Selects the context node parent |
| * | Selects all the child elements of the context node |
| employee | Selects all the employee child elements of the context node |
| s:employee | Selects all the employee child elements of the context node, defined in the namespace with the "s" prefix |
| @numEmployee | Selects the numEmployee attribute of the context node |
| @* | Selects all the attributes of the context node |
| ../@numEmployee | Selects the numEmployee attribute of the context node parent |
| employee[1] | Selects the first employee child element of the context node |
| employee[last()] | Selects the last employee child element of the context node |
| */employee | Selects all the employee grandchildren of the context node |
| //employee | Selects all the employee descendants of the root node |
| .//employee | Selects the employee descendants of the context node |
| company//employee | Selects the employee descendants of the company child elements of the context node |
| //company/employee | Selects all the employee elements with company as parent element in the context node |
| /book/chapter[2]/section[3] | Selects the third section in the second chapter of the book |
| employee[@dept="doc"] | Selects all the employee child elements of the context node with a dept attribute set to doc |
| employee[@dept="doc"][3] | Selects the third employee child element of the context node with a dept attribute set to doc |
| employee[3][@dept="doc"] | Selects the third employee child element of the context node only if it has a dept attribute set to doc |
| chapter[title] | Selects the chapter child elements of the context node with at least one title child element |
| chapter[title="About this book"] | Selects the chapter child elements of the context node with at least one title child element with a text content set to About this book |
| employee[@numEmployee and @dept] | Selects all the employee child elements of the context node with the numEmployee and dept attributes |
| text() | Selects all the child nodes of the text context node |
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