SDL+
The Simplest, Useful
Enhanced SDL-Subset
SDL+
The simplest, useful, enhanced SDL-subset!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
SDL Background
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SDL is a world-leader
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the most popular graphical representation
Special characteristics of SDL are
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Graphical representation
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Hierarchical structure
Functionality
Built-in concepts of states and events
But SDL has become big & complex
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
SDL+ The language of the people!
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The SDL Task Force designed SDL+ to be
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accessible to users with typical requirements
bring implementation and testing closer together
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The starting point is: What is a state machine?
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allowing greater integration of tools
And everything for implementation follows…
Then to ask: What is a test?
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And everything for testing follows…
SDL+ is really easy!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
So What is a State Machine?
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The most basic mechanism in SDL+
Interface
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State
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Defines behaviour for a set of events
State-Event Matrix
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Communication with other state machines
Defines behaviour for the state machine
Context
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Associated information, such as variables
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
State Machine: Interface
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Used for communication with the environment
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Other state machines connected via gates
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Gates are docking points for connections
Communication is based on events
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Protocol Data Unit sent or received at a gate
Typically a list of signals
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Signals have parameters, which must be present if defined
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
State Machine: State
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A state is a set of event constraints
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Each event constraint has a behaviour (action)
An event constraint matches a received event if
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the gate constraint and
the PDU constraint match
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Wildcards for any gate and any PDU
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For signals this means signal name and parameters
Also for any signal and any value
Only one state can be active at a time
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
State Machine: State-Event Matrix
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Defines the behavior for all states
Special states
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Start
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No possible inputs
Defines the behavior when the state machine starts
Default
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Defines the behavior for undefined events
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If not defined in the active state
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
State Machine: Context
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Associated information stored between events
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Variables
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Data types from ASN.1-subset based on X.680
Local variables for procedures
Timers
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
State Machine: Conclusions
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Fully compatible with subset of SDL concepts
Introduction of an extended notion of event
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Any data type
Signal parameter values are checked
Improved scoping & data-hiding
This is already enough to implement
the ITU-T specifications, such as
SS7, ISDN & INAP!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Dimensioning
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Define a specific number of state machines
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Or a specific number of gates
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Arrays of states machines
Arrays of gates
And connect them with a single connection
An index variable is only needed for gates
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Limitations necessary to manage index values
Re-dimension a system by changing
a single parameter.
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
PDU Encoding
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Convert a variable to an ASN.1 encoded PDU
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Convert an ASN.1 encoded PDU to a variable
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ENCODE Variable TO PDU USING Encoding_Rule
DECODE PDU TO Variable USING Encoding_Rule
No additional information needed
No additional ASN.1 compilers needed
Also works for non ASN.1 formatted PDUs!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
PDU Encoding Rules Considered
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Basic Encoding Rules (BER)
Packed Encoding Rules (PER)
Basic Aligned Packed Encoding Rules (BA_PER)
SER (SDL+ Encoding Rule)
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All values as 32 bit integers
SRER (SDL+ Reduced Encoding Rule)
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No tag information, supports non-ASN.1 PDUs
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Encoding / Decoding
• Receive signal with ASN.1 Variable
Protocol stack
• ENCODE Variable TO PDU
• send PDU
ASP for this layer
FSM
SDL-Signals
Codec
Codec
PDUs
ASP* of lower layer
• Receive PDU
• DECODE PDU TO ASN.1Variable
• send Signal
* ASP = Abstract Service Primitive
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
What is a Test?
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A test is
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A sequence of stimuli and expected responses
Chosen to test a specific behaviour
A test result is
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A conclusion reached from carrying out a set of tests
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Recording the individual success of each test
A test results confirms
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the implementation of a test object.
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Testing State Machines with SDL+
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There are many types of testing
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Load tests, functional tests, regression tests...
White box tests, black box tests...
SDL+ is designed for state machines...
...And state machines look like black boxes...
...So SDL+ is designed for black box testing
But SDL+ can probably be used for
any kind of event-based testing!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Potential Benefits
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Data sharing
Portability
Components recycling
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Procedures, signals, user-defined data types
Ease of use – one language instead of two
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Cheaper to implement tools
Faster to learn
Use the same language for
system specification and test specification!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
General Requirements for Test Specifications
Key Requirements
Features used for State Machines
Tester & IUT
Blocks/Processes
Connecting between tester and IUT
Gates & Channels
Communication between tester and IUT
Signals sent & received
Sending stimuli to IUT
Output
Receiving responses from IUT
Input
Storing & Transferring data
Variables & Data Type
Control of Flow
Decisions, Labels & Join
Test Step Replication
Procedures
Measuring the timing of responses
Timers
Implementing a test suite is similar to
implementing a state machine!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Specific Requirements
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A set of tests needs organisation
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Test suite, test groups, test cases and test purpose.
A test needs to check received values are correct
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Constraint
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A test has a conclusion, successful or not
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Verdict (Pass, Fail or Inconclusive)
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Already defined for implementing state machines
Preliminary or Final (end of test)
Configuration data (test suite parameters)
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Change constants without rebuilding
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Interface to Test Object
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A test object is a state machine...
...A state machine has an interface...
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Gates & Events (Signals)
...And a test suite connects to a test object...
...So a test suite has the same interface
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Use same gates & events
Working with the same concepts for implementation
and testing just makes everything much easier!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
SDL+ for Testing
interface
definition
protocol stack
test harness
FSM
test suite
Codec
test object
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
tester
test suite
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Summary of Features for Testing
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Test Suite
Test Group
Test Case
Test Purpose
Matching Mechanism
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Already defined for state machines
Verdict
Test Suite Parameters
SDL+ Sometimes things really can be that simple!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Additional Features Under Consideration
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Test case selection expressions
Parameterized constraint types
Test Suite Variables
Discussion ongoing
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Summary
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SDL+ is lightweight
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But suitable for heavyweight applications
All features are the ‘simplest, useful’
It is almost fully compatible with an SDL-subset
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SDL-2000 could be defined as an extension
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SDL+ has one major difference to SDL...
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...It has features for testing state machines!
One language can be used for the implementation
and testing of state machines!
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org
SDL+
The Simplest, Useful
Enhanced SDL-Subset
Future
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Use SDL+ to promote SDL
Increase acceptance by users
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Improve the documentation
Cooperate with more tool suppliers
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Getting started, tutorials, examples
Embedded systems, safety critical…
Cooperate with the ITU-T!
We need your support – join us at:
www.SDL-Task-Force.org
“The documentation is the design, the design is the system!”
Copyright © 2003-2004 SDL Task Force Consortium. All rights reserved
www.SDL-Task-Force.org