This report defines the Common Platform Enumeration (CPE) Applicability Language version 2.3 specification. The CPE Applicability Language specification is part of a stack of CPE specifications that support a variety of use cases relating to IT product description and naming. The CPE Applicability Language data model builds on top of other CPE specifications to provide the functionality required to allow CPE users to construct complex groupings of CPE names to describe IT platforms. These groupings are referred to as applicability statements because they are used to designate which platforms particular guidance, policies, etc. apply to. This report defines the semantics of the CPE Applicability Language data model and the requirements that IT products and CPE Applicability Language documents must meet for conformance with the CPE Applicability Language version 2.3 specification.