Specification and Description Language

Peyman Dodangeh March 2013

Sharif University of Technology

In The Name Of God

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Summary What is SDL

Intro History Goal SDL Characteristics

SDL Structure References

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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)

Intended for the specification of complex, event-driven, real-time, and interactive application involving many concurrent activities that communicate using discrete signals

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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

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History 1968 ITU study of stored program control

systems

1972 Start of the development

1976 First pre-release

1980-1984Graphics, process semantics, structure, data,definition more rigorous, start of tools, user guide

1988 SDL88, the first standard

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History 1992 SDL92, MSC

intro of OO and methodology guidelines

1995 SDL with ASN.1

1999 SDL-2000 MSC-2000 Object modelling supportImproved implementation support

2001 SDL-2001 Meeting UML

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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

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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

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Application area Type of systems:

Type of information: Level of abstraction:

Real time Interactive Distributed Heterogeneous

Behavior, structure Overview to details

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Use of SDL

SDL(and MSC)

Interpreted as

C++ etc.

Product

used tocreate

used toproduce

SpecificationIdeas

Customer

modelled byDesign

Engineers

Design

Implementation Software

Engineers

modelled by

made as

executesas

Interpreted as

Tools

transformed by

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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

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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)

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SDL Grammars two different syntactic forms (equivalent):

Graphic Representation (SDL/GR) Phrase Representation (SDL/PR)

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SDL Grammars (Cont.) A subset of SDL/PR is common with

SDL/GR called common textual grammar

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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

MSC ASN.1

TTCN

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SDL Structure Comprises four main hierarchical levels:

System Block Process Procedure

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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

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SDL Structure

Repeated block partitioning result in a block tree structure

Partitioned blocks do not contain any process

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SDL Structure Leaf-blocks of a block tree structure are not

partitioned, and contain only process

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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

SystemChannel

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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

1

2

3

5

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Block A block is a part of the system that can be

treated as a self-contained object

c_ins

c_outt

P

1(1)block B

routrin

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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

1

2

5

4

3

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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

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Process A process diagram usually contains the

following elements:1. Process name2. Formal parameters3. Variable descriptions4. Process graph 5. Procedure Descriptions6. Timer descriptions

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Process ExampleProcess P

dcl c character;procedure proc;

c

Proc

FPAR v1 Integer

Proc

123

4

5

c

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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

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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

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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

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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

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Describing behavior with SDL

When a signal has initiated a transition, it is removed from the input queue

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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

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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

ATO P2_ADDRESS

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Implicit Addressing The explicit specification of a destination

address is not necessary if the destination is uniquely defined by the system structure

A

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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

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Process Creation/Termination

A

P2(A,true)

S2

S1

Process P1

Process 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)

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

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

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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

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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

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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)

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References SDL Forum Society http://www.sdl-forum.org

Specification and Description Language Tutorialhttp://www.iec.org/online/tutorials/sdl/

SDL 2001: Meeting UML10th International SDL ForumCopenhagen, Denmark, June 2001ProceedingsRick Reed, Jeanne ReedEd Springer

Documenting Software Architecture: Documenting Behaviorhttp://www.sei.cmu.edu/publications/documents/02.reports/02tn001.htmlBachmann, Bass, Clements, Garlan, Ivers, Little, Nord, Stafford

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References SAM work shop

SDL & MSC workshop (open discussion platform)http://www.irisa.fr/manifestations/2000/sam2000/papers.html

The End