# Package net.sf.saxon.pattern

This package provides classes associated with XSLT pattern handling.

The principal classes are:

Pattern:
This represents an XSLT Pattern. There is a static method Pattern.make() which is used to construct a Pattern from a String (it is a factory method rather than a constructor, because it typically returns some subclass of Pattern according to the syntax supplied). Subclasses of Pattern represent different kinds of pattern such as LocationPathPattern and IDKeyPattern. What they all have in common is a match() method, which determines whether a given node matches the pattern. A pattern is not in itself an Expression, but the class `PatternSponsor` is used to wrap a pattern making it look like an expression for the benefit of the static analysis (allowing the same mechanisms to be used for example to find all the references to a variable).

NodeTest:
This represents a NodeTest within a step of an XPath expression. A NodeTest performs several roles: as well as its use in conjuction with an axis to form a step of a path expression, it acts as an ItemType used in handling type checking of nodes, and (wrapped in a NodeTestPattern) it acts as an XSLT pattern for use in constructs such as the `match` attribute of `xsl:template` and `xsl:key`. A NodeTest is used directly to implement simple patterns such as `match="item"` or `match="*"`. There are several subclasses of NodeTest, depending on the conditions to be matched: node type, node name, namespace URI, and so on. The class AnyNodeTest matches any node, while NoNodeTest matches nothing. NodeTests can also be combined using the operators of intersection, difference, and union, to describe the more complex types that are sometimes computed by the type checking machinery.

- Interface Summary
  Interface | Description
  --- | ---
  PatternParser | Interface to a parser of XSLT patterns.
  PatternWithPredicate | Represents a pattern with a predicate, for example item[@value=3] or .[.
  QNameTest | Interface for tests against a QName.
  SchemaNodeTest | Marker interface for schema-element() and schema-attribute() node tests

- Class Summary
  Class | Description
  --- | ---
  AncestorQualifiedPattern | An AncestorQualifiedPattern represents a path of the form A/B or A//B, where nodes must match the pattern B and also have a parent/ancestor (respectively) that matches A.
  AnchorPattern | This is a special pattern that matches the "anchor node".
  AnyNodeTest | NodeTest is an interface that enables a test of whether a node has a particular name and type.
  BasePatternWithPredicate | Class for handling patterns with simple non-positional boolean predicates
  BooleanExpressionPattern | A BooleanExpressionPattern is a pattern of the form .[ Expr ] introduced in XSLT 3.0.
  CombinedNodeTest | A CombinedNodeTest combines two node tests using one of the operators union (=or), intersect (=and), difference (= "and not").
  ContentTypeTest | NodeTest is an interface that enables a test of whether a node matches particular conditions.
  DocumentNodeTest | A DocumentNodeTest implements the test document-node(element(~,~))
  ExceptPattern | A pattern formed as the difference of two other patterns
  GeneralNodePattern | A GeneralNodePattern represents a pattern which, because of the presence of positional predicates or otherwise, can only be evaluated "the hard way", by evaluating the equivalent expression with successive ancestors of the tested node as context item.
  GeneralPositionalPattern | A GeneralPositionalPattern is a pattern of the form A[P] where A is an axis expression using the child axis and P is an expression that depends on the position.
  IntersectPattern | A pattern formed as the difference of two other patterns
  ItemTypePattern | An ItemTypePattern is a pattern that consists simply of an ItemType; although a node test is an item type, this class is used only for non-node item types, such as atomic types, map types, array types etc.
  LocalNameTest | NodeTest is an interface that enables a test of whether a node has a particular name and type.
  MultipleNodeKindTest | An MultipleNodeKindTest is a nodetest that matches nodes belonging to any subset of possible node kinds, for example element and document nodes, or attribute and namespace nodes
  NamespaceTest | NodeTest is an interface that enables a test of whether a node has a particular name and type.
  NameTest | NodeTest is an interface that enables a test of whether a node has a particular name and type.
  NodeKindTest | NodeTest is an interface that enables a test of whether a node has a particular name and kind.
  NodeSetPattern | A NodeSetPattern is a pattern based on an expression that is evaluated to return a set of nodes; a node matches the pattern if it is a member of this node-set.
  NodeTest | A NodeTest is a simple kind of pattern that enables a context-free test of whether a node matches a given node kind and name.
  NodeTestPattern | A NodeTestPattern is a pattern that consists simply of a NodeTest
  Pattern | A Pattern represents the result of parsing an XSLT pattern string.
  PatternMaker | This is a singleton class used to convert an expression to an equivalent pattern.
  PatternParser30 | Parser for XSLT patterns.
  PatternThatSetsCurrent | This class represents a pattern that sets the value of current() to the node being matched, and then wraps another pattern that uses the value of current()
  SameNameTest | NodeTest is an interface that enables a test of whether a node has a particular name and type.
  SimplePositionalPattern | A SimplePositionalPattern is a pattern of the form A[N] where A is an axis expression using the child axis and P is a numeric literal.
  StreamingFunctionArgumentPattern | This is a special pattern that matches the node supplied as the first argument of a call to a streamable stylesheet function; it corresponds to the pattern match="$arg" where $arg is the first argument of the function.
  UnionPattern | A pattern formed as the union (or) of two other patterns
  UnionQNameTest | A QNameTest that is the union of a number of supplied QNameTests
  UniversalPattern | The UniversalPattern matches everything
  VennPattern | Abstract pattern formed as the union, intersection, or difference of two other patterns; concrete subclasses are used for the different operators