Abstract Development methodologies may be described in the context of an underpinning metamodel, but the precise mechanisms that permit them to be defined in terms of their metamodels are usually difficult to explain and do not cover all needs. For example, it is difficult to devise a practice that allows the definition of properties of the elements that compose the methodology and, at the same time, of the entities (such as work products) created when the methodology is applied. ISO/IEC 24744:2007 introduces the Software Engineering Metamodel for Development Methodologies (SEMDM), a comprehensive metamodel that makes use of a new approach to defining methodologies based on the concept of powertype. The aim of SEMDM is to define methodologies in information-based domains, i.e. areas characterized by their intensive reliance on information management and processing, such as software, business or systems engineering. The SEMDM combines key advantages of other metamodelling approaches with none of their known drawbacks, allowing the seamless integration of process, modelling and people aspects of methodologies. Examples are given where other metamodels are mapped to SEMDM and a brief synopsis of problems is provided. Various methodologies are defined, used, or implied by a growing number of standards, and it is desirable that the concepts used by each methodology be harmonized. A vehicle for harmonization is the SEMDM. Conformance to this metamodel will ensure a consistent approach to defining each methodology with consistent concepts and terminology.