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Designing for Change: Minimizing the Impact of Changing Requirements in the Later Stages of a Spaceflight Software ProjectIn the traditional 'waterfall' model of the software project life cycle, the Requirements Phase ends and flows into the Design Phase, which ends and flows into the Development Phase. Unfortunately, the process rarely, if ever, works so smoothly in practice. Instead, software developers often receive new requirements, or modifications to the original requirements, well after the earlier project phases have been completed. In particular, projects with shorter than ideal schedules are highly susceptible to frequent requirements changes, as the software requirements analysis phase is often forced to begin before the overall system requirements and top-level design are complete. This results in later modifications to the software requirements, even though the software design and development phases may be complete. Requirements changes received in the later stages of a software project inevitably lead to modification of existing developed software. Presented here is a series of software design techniques that can greatly reduce the impact of last-minute requirements changes. These techniques were successfully used to add built-in flexibility to two complex software systems in which the requirements were expected to (and did) change frequently. These large, real-time systems were developed at NASA Langley Research Center (LaRC) to test and control the Lidar In-Space Technology Experiment (LITE) instrument which flew aboard the space shuttle Discovery as the primary payload on the STS-64 mission.
Document ID
19990013874
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Allen, B. Danette (NASA Langley Research Center Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
October 1, 1998
Subject Category
Computer Programming And Software
Report/Patent Number
NAS 1.15:208466
NASA/TM-1998-208466
L-17762
Funding Number(s)
PROJECT: RTOP 258-70-21-10
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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