ISO/IEC/IEEE 31320-2:2012 describes the semantics and syntax of IDEF1X, a language used to represent a conceptual schema. Two styles of IDEF1X model are described.

* The _key style_ is used to produce information models that represent the structure and semantics of data within an enterprise and is backward-compatible with the US government's Federal Information Processing Standard (FIPS) PUB 184, Integration Definition for Information Modeling (IDEF1X).

* The _identity style_ is used to produce object models that represent the knowledge, behaviour, and rules of the concepts within an enterprise. It can be used as a growth path for key-style models. The identity style can, with suitable automation support, be used to develop a model that is an executable prototype of the target object-oriented system.