Abstract: A method for processing queries is provided. A database server receives and executes a query to generate a relation. The query comprises first one or more clauses and a model clause. The model clause comprises a rule that has a left-side expression and a right-side expression. In one embodiment, the right-side expression of the rule includes a window function, which specifies one or more partition columns. In an embodiment, the left-side expression comprises a for-loop predicate. The for-loop predicate is unfolded after the database server compiles the query. In one embodiment, the left-side expression of the rule comprises one or more existential predicates, where each existential predicate evaluates to a Boolean value.