A Generic Model for the Specification of Software Interface Requirements and Measurement of their Functional Size

The European ECSS-E-40 series of standards for the aerospace industry includes interfaces as one of 16 types of non functional requirement (NFR) for embedded and real-time software. An interface is typically described at the system level as a non functional requirement, and a number of concepts and terms are provided in that series to describe various types of candidate interfaces. This paper collects and organizes these interface-related descriptions into a generic model for the specification of software interface requirements, and to measure their functional size for estimation purposes using the COSMIC ISO 19761 standard.