Specification and Description Language Peyman Dodangeh March 2013 Sharif University of Technology In The Name Of God

2 Summary What is SDL Intro History Goal SDL Characteristics SDL Structure References

3 What is SDL SDL (Specification and Description Language) is an object-oriented, formal language developed and standardized by The International Telecommunication Standardization Sector (ITU-T)ITU-T Intended for the specification of complex, event-driven, real-time, and interactive application involving many concurrent activities that communicate using discrete signals

4 What is SDL SDL describe the architecture, behavior and data of distributed systems in real time environments Useful for specifying the normative requirements of telecommunications protocol standards Wide spectrum language - specification to implementation

5 History 1968 ITU study of stored program control systems 1972 Start of the development 1976 First pre-release Graphics, process semantics, structure, data, definition more rigorous, start of tools, user guide 1988 SDL88, the first standard

6 History 1992 SDL92, MSC intro of OO and methodology guidelines 1995 SDL with ASN SDL-2000 MSC-2000 Object modelling support Improved implementation support 2001 SDL-2001 Meeting UML

7 Goals Provide a better way to describe behavior Support human communication and understanding Easy verification conformance of implementation of specifications Design optimization Analyzing specifications for completeness and correctness

8 Goals Use of computer based tools to create, maintain and analyze specifications Formal high quality descriptions produced better, quicker and cheaper Provide to programmers an easy way to do verification, validation of the design, regression testing, automatic documentation and simplified maintenance

9 Application area Type of systems: Type of information: Level of abstraction: Real time Interactive Distributed Heterogeneous Behavior, structure Overview to details

10 Use of SDL SDL (and MSC) Interpreted as C++ etc. Product used to create used to produce Specification Ideas Customer modelled by Design Engineers Design Implementation Software Engineers modelled by made as executes as Interpreted as Tools transformed by

11 SDL Characteristics Graphical form Based on communicating processes OO description of components Formality and clarity High degree of testability Portable, scalable, open, reusable SDL-GR Graphical notation for SDL SDL-PR Textual notation for SDL

12 Examples Cellular phones Switches GPRS UMTS GSM ISDN

Commercial SDL Tools both developed by Telelogic: - ObjectGeode - Telelogic Tau SDL Suite (ObjectGeode has been developed by Verilog, but in 1999, Telelogic has acquired Verilog) 13

SDL Grammars two different syntactic forms (equivalent): Graphic Representation (SDL/GR) Phrase Representation (SDL/PR) 14

SDL Grammars (Cont.) A subset of SDL/PR is common with SDL/GR called common textual grammar 15

16 SDL & others languages SDL is well suited to be the core of full-scale projects because of its abilities to interface with other languages. UML MSCASN.1 TTCN

17 SDL Structure Comprises four main hierarchical levels: System Block Process Procedure

18 SDL Structure A system contains one or more blocks, interconnected with each other and with the boundary of the system by channels The block is the main structuring concept A block can be partitioned into sub-blocks and channels A channel is a means of conveying signals

19 SDL Structure Repeated block partitioning result in a block tree structure Partitioned blocks do not contain any process

20 SDL Structure Leaf-blocks of a block tree structure are not partitioned, and contain only process

21 System The system description constitutes the top level of detail The system is what the SDL description specifies: an abstract machine communicating with its environment Environment System Channel

22 System A system diagram usually contains the following elements: 1. system name 2. signal descriptions 3. channel descriptions 4. data type descriptions 5. block descriptions

24 Block A block is a part of the system that can be treated as a self-contained object

25 Block A block diagram usually contains the following elements: 1. block name 2. signal descriptions 3. signal route descriptions 4. channel-to-route connections 5. process descriptions

27 Process A process in SDL is an extended finite state machine The behavior of a finite state machine is described by states and transitions A process description is given through a process diagram In SDL there are five basic constructs for the description of a process task

28 Process A process diagram usually contains the following elements: 1. Process name 2. Formal parameters 3. Variable descriptions 4. Process graph 5. Procedure Descriptions 6. Timer descriptions

29 Process Example Process P dcl c character; procedure proc; c Proc FPAR v1 Integer Proc c

30 Procedure The procedure construct in SDL is similar to the one known from programming languages A procedure is a finite state machine within a process. It is created when a procedure call is interpreted, and it dies when it terminates A procedure description is similar to a process description, with some exceptions. The start symbol is replaced by the procedure start symbol

31 Procedure A return symbol is introduced: When a procedure is running, the calling process or procedure is suspended in the transition containing the procedure call

32 Describing behavior with SDL The behaviour of a system is constituted by the combined behaviour of the processes in the system A process is defined as finite state machine, that works autonomously and concurrently with other processes A process reacts to external stimuli in accordance with its description A process is either in a state waiting, or performs a transition between two states

33 Describing behavior with SDL The co-operation between the processes is performed asynchronously by discrete messages called signals Every process has an infinite input queue associated, which acts like a FIFO queue Any signal arriving at the process is put into its input queue

34 Describing behavior with SDL When a signal has initiated a transition, it is removed from the input queue

35 Process Addressing Every process has a unique address The address is not determined by the user, but is rather created by some abstract SDL machine during the creation of a process For any signal sent by a process there must be one and only one destination Destination can be specified: Implicitly explicitly

36 Explicit Addressing SDL has the TO construct for the explicit addressing of processes The keyword TO is used in an output, and it is followed by an expression containing the address of the destination process A TO P2_ADDRESS

37 Implicit Addressing The explicit specification of a destination address is not necessary if the destination is uniquely defined by the system structure A

38 Process Creation/Termination Processes can be created by other processes dynamically at interpretation time This is indicated in a block diagram by a dashed line from the creating process to the created process The creating and created process must belong to the same block

39 Process Creation/Termination A P2(A,true) S2 S1 Process P1Process P2 dcl v3 Integer V3 = v1 * 2 v3 FPAR v1 Integer, v2 Boolean

Text and Task Symbols keyword DCL introduces definition of variables in a text symbol during transition the process can manipulate its own local variables a task construct is always an assignment (represented by a task symbol) 40

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Decision Symbol question may have various answers only one answer should be correct 42

decision symbol may have a number of different shapes. Some examples are: 43

Data Carrying Signals signals can carry data values from one process to another In the input construct, variables are specified output construct includes data values types of values sent in output construct must be compatible with types of variables in the corresponding input construct 44

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When signal A is consumed by process p2, the value 5 is assigned to v1 and true is assigned to v2 In the input and output constructs, the order of the data values and variables is important 46

one or more values may be omitted in an output construct one or more variables may be omitted in the input construct (corresponding received values are lost in this case) 47

48 References SDL Forum Society Specification and Description Language Tutorial SDL 2001: Meeting UML 10 th International SDL Forum Copenhagen, Denmark, June 2001 Proceedings Rick Reed, Jeanne Reed Ed Springer Documenting Software Architecture: Documenting Behavior Bachmann, Bass, Clements, Garlan, Ivers, Little, Nord, Stafford

49 References SAM work shop SDL & MSC workshop (open discussion platform)

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