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| SC.3 Grand Design (Traditional Procedure) |
SZ.3 Grand Design (Traditionelles Vorgehen)
SC.3.1 Sequence Description for the Activities in Submodel SD
The traditional procedure for a system development is frequently referred to as "Big Bang", "One Shot" or "Grand Design".
Typical in this procedure is the linear chronological course of the system development (phase model). During each phase, the entire System is handled in its complete functionality. The complete conclusion of a phase is the requirement for the beginning of the next phase.
Therefore, the traditional procedure is a special case in the incremental development (realization in increments). The sequence of SD activities during the Grand Design are illustrated in Figure SC.3.
Figure SC.3: Sequence of SD Activities in Grand Design
Time T 0-Start
Initialization of project and beginning of activities with regard to the contents of submodel SD.Time T 1-Complete User Requirements
From the point of view of activity SD1 - System Requirements Analysis, the System has been completely processed at T1. This means:- The User Requirements have been completely processed.
- The System has been completely structured into segments.
- The Technical Requirements to the System have been completely defined.
Time T 2-Completion of the System Development and System Transition
At time 2, the system development is completed and the System transferred for use.The following steps are required for the realization:
- If segments were identified in the System Architecture during activity SD2 - System Design, the Technical Requirements for these segments are completely specified and they are completely decomposed into SW and HW Units (activity SD2).
- The Technical Requirements are completely specified for the identified SW Units/HW Units. The generation of the Technical Requirements is thus completed (activity SD3 - SW/HW Requirements Analysis).
- All identified SW Units/HW Units are completely realized (activities SD4 - Preliminary SW Design to SD7 - SW Integration).
- The realized SW Units/HW Units are integrated into the System (activity SD8 - System Integration).
SC.3.2 Cooperation with the other Submodels
SC.3.2.1 Cooperation with Submodels SD and PM
The schematically regulated and relatively rigid development procedure of a project as the one just described can-with sufficient experience in the application field-be planned and realized with foresight and limited risks by the specification of requirements.
The special problematics of the phase-oriented procedure are based on the limited and costly mechanisms for the consideration of unexpected changes and the inexperienced handling of requirements insufficiently or badly explained.
Based on experience, such a procedure can be dependably and successfully applied only when requirements are very clearly defined and when technical and user-level risks for the project are low.
Therefore, one of the special tasks of the PM is a sensible risk management that detects risks at a very early stage and is thus able to change the development strategy.
SC.3.2.2 Cooperation of Submodels SD and QA
Based on changes detected and specified early, the quality assurance tasks must be planned and realized regularly. If the above mentioned risks can be eliminated, no special procedures with regard to quality assurance have to be observed.
SC.3.2.3 Cooperation of Submodels SD and CM
The structured generation of the System according to the product structure is covered in the regulations of the configuration management. Since the System transfer into the system application is realized with one step, the delivery is simple.
SC.3.3 Criteria for the Selection of Scenarios
The following list of advantages and disadvantages and the listing of the most important requirements support decision-making for the selection of the illustrated Grand Design procedure.
Advantages:
- Great planning and handling experience based on the availability of stable User Requirements,
- problem-free change of contractor after completion of each phase.
- Inflexible reaction to unpredictable changes,
- necessity of early definition of User Requirements and the corresponding specification for the entire development time,
- late System delivery.
- Stable User Requirements.
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This page online • GDPA Online • Last Updated 03.Mar.2004 by C. Freericks |