1.2 PHASES, ACTIVITIES AND MILESTONES
The software life cycle starts when a software product is conceived and ends when it is no longer available for use, i.e. it contains the whole of the development, operations and maintenance activities.
The products of a software development project shall be delivered in a timely manner and be fit for their purpose. Software development activities shall be systematically planned and carried out. A ‘life cycle model’ structures project activities into ‘phases’ and defines what activities occur in which phase. Figure 1.2 shows the life cycle model used in these Standards. A ‘life cycle approach’ is a combination of the basic phases of the life cycle model. Section 1.3 describes three possible life cycle approaches which cover most of the needs of the Agency. All software projects shall have a life cycle approach which includes the basic phases shown in Figure 1.2:
· UR phase - Definition of the user requirements
· SR phase - Definition of the software requirements
· AD phase - Definition of the architectural design
· DD phase - Detailed design and production of the code
· TR phase - Transfer of the software to operations
· OM phase - Operations and maintenance
Replaced/Superseded by document(s)
1 PURPOSE OF THE STANDARDS
This document describes the software engineering standards to be applied for all deliverable software implemented for the European Space Agency (ESA), either in house or by industry. Software is defined in these Standards as the programs, procedures, rules and all associated documentation pertaining to the operation of a computerised system. These Standards are concerned with all software aspects of a system, including its interfaces with theomputer hardware and with other components of the system. Software may be either a subsystem of a more complex system or it may be an independent system. Where ESA PSS-01-series documents are applicable, and as a consequence ESA PSS-01-21, ‘Software Product Assurance Requirements for ESA Space Systems’ is also applicable, Part 2, Chapter 5 of these Standards, ‘Software Quality Assurance’, ceases to apply.