Package org.opengis.filter.expression

Combinations of one or more elements that evaluate to single Object value. The following is adapted from Filter encoding specifications:

An expression can be formed using the elements: Add, Subtract, Multiply, Divide, PropertyName, Literal and Function. They all belong to the substitution group expression which means that any of them can be used wherever an expression is called for. In addition, the combinaison of these elements are themselves expressions and can be used wherever an expression is called for.

Arithmetic operators

The elements defined in this package are used to encode the fundamental arithmetic operations of addition, subtraction, multiplication and division. Arithmetic operators are binary operators meaning that they accept two arguments and evaluate to a single result.


A literal value is any part of a statement or expression that is to be used exactly as it is specified, rather than as a variable or other element. The Literal element is used to encode literal scalar and geometric values.


A function is a named procedure that performs a distinct computation. A function may accept zero or more arguments as input and generates a single result. A function is composed of the name of the function, encoded using the attribute name, and zero or more arguments contained within the Function element. The arguments themselves are expressions.

Data Access

Data access is accomplished by means of PropertyName expressions. These Expressions are independent of the data being queried and form the foundation of a, very simple, general query language offering independence specific bindings to Feature, Metadata and Record data structures.

Filter Encodings

At the time of this writing the Filter API has standard encodings for XML (Filter 1.0 and Filter 1.1) and Text (a BNF form is provided in the Catalog 2.0.1 specification above). You should be warned that not all content can be expressed in all encodings, please refer to the javadocs for specific limitations.