Expressions are analogous to functions, and tell Forge which records, properties, or dimensions to affect, and how to affect them.

Record manipulator components do their work on record data by means of expressions. Record manipulator components can contain an arbitrary number of expressions which are evaluated against each record as Forge processes it. When Forge evaluates an expression, it may modify the current record. The changes take a variety of forms depending on the expression, from adjusting property values to creating new data.

Expressions can contain sub-expressions; the sub-expressions may provide values used by the parent expression, or the parent expression may provide control over which of the sub-expressions are evaluated. Also, many expressions contain expression nodes, which are name/value pairs that specify property names, constant values, dimension IDs, and so forth. Expression nodes represent parameters required by the expression. If a parent expression contains both sub-expressions and expression nodes, the nodes must be placed before the sub-expressions.

In Developer Studio, you write and modify expressions in the Record Manipulator component's XML editor. The following is an example of a record manipulator component with expressions, sub-expressions, and expression nodes.

See the Endeca Data Foundry Expression Reference for complete details on all expressions and their syntax. In addition, the documentation for the advanced features that use expressions provide detailed examples.