Xpath

前言: Xpath, 就把它当做一棵树的查找！！

Xpath Data Model

• Sequences and items
  The XPath data model is based on the notion of a sequence. The value of an XPath expression is always a sequence. A sequence is an ordered collection of zero or more items. An item is either an atomic value or a node.

• Atomic values
  An atomic value is an instance of one of the built-in atomic data types that are defined by XML Schema.These data types include strings, integers, decimals, dates, and other atomic types.

• Nodes
  A node conforms to one of the types of nodes that are defined for XPath. These node types include: document, element, attribute, text, processing instruction, comment, and namespace nodes.

  • Document nodes
    A document node encapsulates an XML document.
  • Element nodes
    An element node encapsulates an XML element.
  • Attribute nodes
    An attribute node represents an XML attribute.
  • Text nodes
    A text node encapsulates XML character content.
  • Processing instruction nodes
    A processing instruction node encapsulates an XML processing instruction.
  • Comment nodes
    A comment node encapsulates XML comments.

Relationship of Nodes

• Parent
  Each element and attribute has one parent.

• Children
  Element nodes may have zero, one or more children.

• Siblings
  Nodes that have the same parent.

• Ancestors
  A node's parent, parent's parent, etc.

• Descendants
  A node's children, children's children, etc.

Xpath Syntax

• W3schools: Xpath Syntax

• MSDN: Xpath Syntax

• 栗子: List_of_XPaths

Location Path

• Location Steps

axis::nodetest[predicate]

• Axes

• Node Tests

• Predicates

Xpath functions

• MSDN: Xpath Functions

• W3Schools: XSLT, XPath, and XQueryFunctions