Embodiments of the present invention provide a method, system and computer program product for expression evaluation of content instances of multiple different data models. In an embodiment of the invention, a method for expression evaluation of content instances over multiple different data models comprises loading a schema for a content instance in memory of a computer and evaluating an expression against the content instance. In response to a failure during the evaluation of the expression against the content instance to resolve a reference to an element specified by the expression, an alias reference for the element can be identified in the schema and the evaluation can be completed using the alias reference in lieu of the specified reference.