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Annex 2  
2.8 The Complex Method SSADM  

  SSADM - Structured Systems Analysis and Design Method

  • 1 Brief Description
  • 2 Tabular Comparison
  • 3 Specification of the Allocation
  • 4 Literature
  • 1 Brief Description

    During the beginning of the Eighties, the complex method SSADM (Structured Systems Analysis and Design Method) was developed on behalf of the British government by the consulting company LBMS-Learmonth & Burchett Management Systems in cooperation with CCTA (Central Computer Telecommunications Agency). In 1983, SSADM was declared as the standard to be applied for DP development projects of the British government. Since then, it has been permanently upgraded. The present valid SSADM version is Version 4 (since July 1990) /Downs, 1992/.

    The application of SSADM aims at the development of information systems on the basis of database systems and less at the development of real-time-oriented software. Therefore, the method concentrates on data flows, data models, and-as a specialty-the chronological life cycles of entities.

    Contrary to the strict separation of procedure and method in the software development standard of the German Federal Armed Forces, a lifecycle process model has been integrated into the method in SSADM.

    The lifecycle process model of SSADM supplies both detailed procedures and instructions for analysis and design in connection with software generation (SD1 - System Requirements Analysis to SD5 SW - Detailed SW Design) in the following areas:

    However, all implementation and integration activities have been excluded on purpose. In the same way are the accompanying activities of submodels PM, CM, and QA not subject of SSADM but distributed to special methods (e. g. PRINCE, CRAMM).

    The following comparison refers to the methodical components of SSADM in the sense of the GD 251. In SSADM, they are referred to as Techniques. These techniques include:

    2 Tabular Comparison

    The following table compares the basic methods of the GD 251 with the methodical components of SSADM. In the case where there is no entry in the right column of the table, SSADM has no corresponding component. Otherwise, an entry refers to the corresponding part in the literature. Section 3 of the comparison contains an explanation for the entry. Entries identified by (*) refer to basic methods completely covered by SSADM. These are not further described in section 3.

    Comparison of the Basic Methods and the
    Methodological Components of SSADM
    AUD - Audit  
    ACC - Analysis of Covert Channels  
    BAR - Bar Plan  
    TREE - Tree Diagram  
    BBTD - Black Box Test Case Design  
    CRC - Class Responsibility Collaboration  
    DIAL - Dialog Design Modeling Dialog Design
    /Downs, 1992/ chap. 3.4
    DFM - Data Flow Modeling Data Flow Modeling
    /Downs, 1992/ chap. 3.5
    DNAV - Data Navigation Modeling Logical Data Modeling
    /Downs, 1992/ chap. 3.6
    DVER - Design Verification  
    ELH - Entity Life History Entity Event Modeling
    /Downs, 1992/ chap. 3.11
    ER - E/R Modeling Logical Data Modeling
    /Downs, 1992/ chap. 3.6 (*)
    DTAB - Decision Table Technique  
    EVT - Earned Value Method  
    EXPM - Expertise Model  
    FCTD - Functional Decomposition Data Flow Modeling
    /Downs, 1992/ chap. 3.5
    FMEA - Failure Mode Effect Analysis  
    FNET - Function Net Modeling  
    FS - Formal Specification  
    IAM - Interaction Modeling  
    CFM - Control Flow Modeling  
    COM - Class/Object Modeling  
    LOGM - Logical DB Modeling Relational Data Analysis
    /Downs, 1992/ chap. 3.9
    MODIAG - Module Diagrams  
    NORM - Normalization Relational Data Analysis
    /Downs, 1992/ chap. 3.9 (*)
    NPT - Network Planning Technique  
    BA - Benefit Analysis  
    ODT - Object Design Technique  
    OGC - Organizational Chart  
    PCODE - Pseudocode Logical Database Process Design
    /Downs, 1992/ chap. 3.13
    PRODIAG - Process Diagrams  
    PVER - Program Verification  
    PIM - Process Interaction Modeling  
    REV - Review  
    SIMU - Simulation Models  
    EMOD - Estimation Models  
    SSM - Subsystem Modeling  
    STAT - Static Analysis  
    STRD - Structured Design Entity Event Modeling Logical Database Process Design /Downs, 1992/ chapters 3.11 and 3.13
    SBM - System Behavior Models  
    T - Test  
    TRDA - Trend Analysis  
    UCM - Use Case Modeling  
    WBTD - White Box Test Case Design  
    STM - State Transition Modeling  
    STMO - State Modeling in the OO Field  
    RELM - Reliability Models  

    Table 2.8: Basic Methods-SSADM

    3 Specification of the Allocation

    in SSADM
    Dialog Design Modeling
    /Downs, 1992/ chap. 3.4 "Dialog design", p. 96 The method Dialog Design has two "subtechniques":
    • within the scope of the "dialog identification", the first step identifies the users and the functionality they request for the information system to be realized,
    • in the second step there is a logic "dialog design" in which information flows from and to the information system are described.
    The generation of the mask layouts or the implementation of the dialogs are not a subject of the method.
    Data Flow Modeling
    /Downs, 1992/ chap. 3.5 "Data flow modeling", p. 103 The data flow modeling in SSADM covers the basic method DFM completely. In addition to the graphical means of representation "process", "terminator", "data flow", and "data store" required in DFM, so-called physical flows exist in SSADM to describe the material flow between users (terminators) and the system to be modeled (processes). They are used for the user-level description and are only applied on the highest level in data flow diagrams.
    Data Navigation Modeling
    /Downs, 1992/ chap. 3.6 "Logical data modeling", "Enquiry access paths", p. 136 Based on the E/R diagram and the identified functions of the information system, the name of the query is defined for all database queries to be realized, the initiating event and the data affected by the query (key, selection criteria), and the path through the data model at the time of the query execution are described.
    Entity Life History
    /Downs, 1992/ chap. 3.11 "Entity event modeling", "Entity Life History", p. 170 All of the possible operational sequences are graphically described for each entity type during the life cycle of that entity. Means of representation are Structure Charts. ELHs are used to check the completeness of the functional description, to describe interdependencies between functions, and to derive test cases.
    Functional Decomposition
    /Downs, 1992/ chap. 3.5 "Data flow modeling", p. 103 The functional decomposition is implicitly contained in technique "Data Flow Modeling". The processes identified during the analysis of the data flows are hierarchically refined on lower levels. The processes generated during the data flow modeling can be arranged into a tree structure.
    Logical DB Modeling
    /Downs, 1992/ chap. 3.9 "Relational data analysis", p. 149 Technique "relational data analysis" completely covers the basic method LOGM for the area of relational database systems. The result of the E/R model conversion are tables describing the keys and attributes of the entities. Relationships between entities are (after prior normalization) realized by means of external keys.
    /Downs, 1992/ chap. 3.13 "Logical database process design", p. 198 The logical database process design is used to describe processes that are accessing a database. Processes receiving or sending data via the user interface or those mapping technical aspects are not described.

    The result of this description is a Process Structure Diagram which is upgraded by operations and control structures.

    Structured Design
    /Downs, 1992/ chap. 3.11 "Entity event modeling" p. 170; chap. 3.13 "Logical database process design", p. 198 The Structure Charts from STRD are applied at various places in SSADM. On the one hand, Entity Life Histories are illustrated with the help of Structure Charts, on the other hand they are utilized in connection with the description of the structure of processes.

    4 Literature

    /Downs, 1992/ Structured Systems Analysis and Design Method, Application and Context

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