# Package org.zkoss.xel

- Interface Summary
  Interface | Description
  --- | ---
  Expression | Represent a prepared (a.k.a., compiled) expression.
  ExpressionFactory | Used to prepare expressions (`Expression`).
  ExpressionX | An extension of `Expression` to have more control to handle Expression Language EL 2.2 specs.
  Function | Represents a XEL function.
  FunctionMapper | Used to customize the way to map between the XEL function names and the `Function` methods.
  FunctionMapperExt | Implemented with `FunctionMapper` to resolve the class.
  ValueReference | This represents a base model object and one of its properties (EL 2.2).
  VariableResolver | Used to customize the way an `Expression` resolves variable references at evaluation time.
  VariableResolverX | An extension of `VariableResolver` to have more control to resolve the variables.
  XelContext | Context information for XEL evaluation.

- Class Summary
  Class | Description
  --- | ---
  Expressions | Utilities to use XEL.
  XelException.Aide | Utilities.

- Exception Summary
  Exception | Description
  --- | ---
  XelException | Represents a XEL exception.