There are a number of Operations in Cascading that will compile and apply Java expressions on the fly, see ExpressionFunction and ExpressionFilter for examples. In these expressions, Operation argument field names are used as variable in the expression. When creating field names, be conscious of the fact that if they are used in an expression, some characters will cause compilation errors. For example, "first-name" is a valid field name for use with Cascading, but this expression, first-name.trim(), will fail.