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Annex 2  
2.6 The Complex Method SDL  

  SDL - Specification and Description Language

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

    SDL (Specification and Description Language) is a formal language with the aim to specify and describe the behavior of telecommunication systems (in particular with regard to the function areas Call Processing, Maintenance, Error Handling, System Control, and the design of data communication protocols). Based on its features, SDL can generally be applied for the behavior specification of real-time systems. The language is defined in graphical and textual notation. SDL includes a number of concepts, like type, instance, communication and visibility concepts as well as a dynamic semantics. SDL is represented in form of blocks, channels, processes, signals, and system diagrams.

    The methodical components of SDL are:

    2 Tabular Comparison

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

    Comparison of the Basic Methods and the
    Methodological Components of SDL
    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  
    DFM - Data Flow Modeling BID Block Interaction Program
    /SDL, 1985a/, Z.100, chap. 2.4
    DNAV - Data Navigation Modeling  
    DVER - Design Verification  
    ELH - Entity Life History  
    ER - E/R Modeling  
    DTAB - Decision Table Technique  
    EVT - Earned Value Method  
    EXPM - Expertise Model  
    FCTD - Functional Decomposition HD Hierarchical Decomposition,
    /SDL, 1985a/, Z.102, chap. 2.1
    BP Decomposition of Blocks into Processes,
    /SDL, 1985a/, Z.100, chap. 2.2
    FMEA - Failure Mode Effect Analysis  
    FNET - Function Net Modeling  
    FS - Formal Specification  
    IAM - Interaction Modeling  
    CFM - Control Flow Modeling PD Process Diagram
    /SDL, 1985a/, Z.100, chap. 2.2
    COM - Class/Object Modeling  
    LOGM - Logical DB Modeling  
    MODIAG - Module Diagrams  
    NORM - Normalization  
    NPT - Network Planning Technique  
    BA - Benefit Analysis  
    ODT - Object Design Technique  
    OGC - Organizational Chart  
    PCODE - Pseudocode  
    PRODIAG - Process Diagrams  
    PVER - Program Verification  
    PIM - Process Interaction Modeling PD Process Diagram
    /SDL, 1985a/, Z.100, chap. 2.2
    Time Sequence Diagrams
    /SDL, 1991/, chap. 9.1.3, 9.4.1
    REV - Review  
    SIMU - Simulation Models PD Process Diagram
    /SDL, 1985a/, Z.100, chap. 2.2
    Time Sequence Diagrams
    /SDL, 1991/, chap. 9.1.3, 9.4.1
    Message Sequence Chart (MSC),
    /SDL, 1992/, Z.120
    EMOD - Estimation Models  
    SSM - Subsystem Modeling  
    STAT - Static Analysis GS Validity Rules
    /SDL, 1985a/, Z.100, chap. 2.1, 3
    /SDL, 1985a/, Z.101, chap. 2, 4
    STRD - Structured Design  
    SBM - System Behavior Models PD Process Diagram
    /SDL, 1985a/, Z.100, chap. 2.2
    T - Test MAP Ability to be Mapped
    /SDL, 1985b/, Annex D, chap. D.8.1
    TRDA - Trend Analysis  
    UCM - Use Case Modeling  
    WBTD - White Box Test Case Design  
    STM - State Transition Modeling PD Process Diagram
    /SDL, 1985a/, Z.100, chap. 2.2
    STMO - State Modeling in the OO Field  
    RELM - Reliability Models  

    Table 2.6: Basic Methods-SDL

    3 Specification of the Allocation

    MethodCorresponding
    Component
    in SDL
    Explanation
    DFM
    Data Flow Modeling
    BID Block Interaction Diagram /SDL, 1985a/, Z.100, chap. 2.4 In the static semantic, data flows and channels or respectively DFM processes and SDL blocks are very similar, with the exception of the data itself. In SDL these data are type-bound signals right from the beginning. In the dynamic semantic, DFM processes, SDL blocks, and SDL processes are very different from each other. With regard to DFM it is assumed (in a simplified way) that a process automatically generates output data, i. e. if all input data are available. SDL blocks, however, have no dynamic behavior; this is exclusively found in the SDL processes contained in the block.
    FCTD
    Functional Decomposition
    HD Hierarchical Decomposition, /SDL, 1985a/, Z.102, chap. 2.1 BP Decomposition of Blocks into Processes, /SDL, 1985a/, Z.100, chap. 2.2 The basic characteristics of the FCTD correspond to those in the SDL to a great extent. It must be noted that new blocks are generated in connection with the refinement of channels. Furthermore, process tree diagrams must be adjusted to the corresponding block tree diagrams by taking into consideration certain consistency rules.
    CFM
    Control Flow Modeling
    (with limitations since only STM processes) PD Process Diagram /SDL, 1985a/, Z.100, chap. 2.2 SDL contains no directly corresponding methodical component to CFM. However, the functionality of CFM is contained in SDL in a distributed way. Based on two reasons, a direct correspondence is not possible: SDL does not separate control and data information but signals which might basically contain both. Also, SDL does not differentiate between (data processing) processes (PSPECs) and control information processing (CSPECs); it only contains a basic process type that is always a sequential automaton, processing all of the information. Furthermore, SDL does not contain a store (that can be overwritten) according to CFM and DFM.

    The methodically advantageous separation of the processing of control and data information (as in DFM and CFM) can be reconstructed in SDL, if required. In this connection, all SDL (control of a decomposition level) processes are combined in one SDL block, and the only task of the SDL block is to control the activity of the remaining processes in the other blocks.

    PIM
    Process Interaction Modeling
    PD Process Diagram /SDL, 1985a/, Z.100, chap. 2.2
    Time Sequence Diagrams /SDL, 1991/, chap.9.1.3, 9.4.1
    Message Sequence Chart (MSC), /SDL, 1992/, Z.120
    Though the time sequence diagrams listed in /SDL, 1991/ are no integral part of the SDL standard, they are a particularly appropriate technique for the cooperation with SDL. /SDL, 1992/ contains a version of this technique upgraded into a method that is applicable for the integration with SDL. Time Sequence Diagrams and the simpler forms of Message Sequence Charts largely correspond to PIM.
    SIMU
    Simulation Models
    PD Process Diagram /SDL, 1985a/, Z.100, chap. 2.2
    Time Sequence Diagrams /SDL, 1991/, chap.9.1.3, 9.4.1
    Message Sequence Chart (MSC), /SDL, 1992/, Z.120
    The exactly defined dynamic semantic of SDL permits the access to the SDL design of an automatic interpretation. Thus-when working with SDL-it is not necessary to construct a separate simulation model within the scope of SIMU but the available SDL design can be utilized by means of corresponding tools. The generation of the required scenario data can be supported by means of Time Sequence Diagrams or Message Sequence Charts.
    STAT
    Static Analysis
    GS Validity Concept /SDL, 1985a/, Z.100, chap. 2.1, 3 /SDL, 1985a/, Z.101, chap. 2, 4 SDL specifications are formal structures that have to meet the syntax and semantics defined in /SDL, 1985a/, Z.101, chap. 2 and 4. Therefore they are open for a tool-supported consistency check in which connection user errors in the sense of STAT are detected at an early stage. It must be stressed that the assessability also refers to the dynamic semantics (s. /SDL, 1985a/, Z.100, chap. 2.1, "Specification Error").
    SBM
    System Behavior Models
    PD Process Diagram /SDL, 1985a/, Z.100, chap. 2.2 The SDL concepts generally aim at uniquely specifying the dynamic behavior of an event-oriented real-time system with concurrent processes. Since SDL specifications are also formal, SDL meets the SBM requirements completely. In connection with the SDL application, special attention must be paid to the characteristics of the automaton model and the communication concept (e. g. signal input queue, possible zero transitions when utilizing signals).
    T
    Test
    MAP Mapping /SDL, 1985b/, Annex D, chap. D.8.1 The dynamic semantics of SDL makes it possible to execute an available SDL design by means of the corresponding tools. Those tools usually contain a test frame (i. e. the interpreter for the execution) as well as test recording features. The generation of the required test cases can be supported by means of Time Sequence Diagrams or Message Sequence Charts. The high degree of detail and the comprehensibility of SDL specifications based on the Type and Visibility concepts support the definition of test cases rich in content. Furthermore, MAP supports the automatic generation of source code from an SDL design and the corresponding test while eliminating transformation errors due to human failure.
    STM
    State Transition Modeling
    PD Process Diagram /SDL, 1985a/, Z.100, chap. 2.2 The basic concept of the upgraded sequential automaton utilized for the process diagram in SDL is identical to model STM. The structural peculiarities of the SDL processes consist in local data, additional branching, and the fact that only one waiting queue exists for all input signals of a process (no separate waiting queue for individual process states).

    4 Literature

    /SDL, 1985a/ Functional Specification and Description Language (SDL) - Vol.VI.10
    /SDL, 1985b/ Functional Specification and Description Language (SDL) - Vol.VI.11
    /SDL, 1991/ SDL with Applications from Protocol Specification
    /SDL, 1992/ Message Sequence Chart (MSC)

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