Marc Geilen, Eindhoven University of Technology, Information and Communication Systems 1 Object-Oriented Modelling and Specification using SHE M. Geilen, J. Voeten Information and Communication Systems Department of Electrical Engineering Eindhoven University of Technology The Netherlands >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 2 Contents Introduction: SHE System Level Modelling The POOSL Language Example and tools Conclusions & Further Research >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 3 Software / Hardware Engineering >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 4 1:a 2:b 5:c o1o2o3 Interaction Diagrams Initial Requirements POOSL formalisation functional behaviour, structure, communication, real-time Object o1 (class A) Object o2 (class A) Object o3 (class B) message b message c Message Flow Diagrams Requirements Catalogue SHE Methodology Framework Object Class Diagram Messages: Attributes: P: Class A Relationship x Messages: m Attributes: P: Class B Architecture Structure Diagrams M2M1 network Instance Structure Diagrams Object o1 (class A) Object o3 (class B) Object o2 (class A)

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 5 Object Class Diagram

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 6 SHE: Message Flow Diagram

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 7 Introduction: System Level Modelling >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 8 Design Decisions and Models  Investigation of design alternatives to obtain a satisfying realisation.  Realising design alternatives to determine the values of these properties is too costly and time-consuming.  Values of properties must be determined from models.  A model is an abstract representation of some design realisation.  A model must be adequate for the properties that are relevant for making a design decision. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 9 System Level Modelling  If a model is more abstract  it will in general be adequate for less properties with less accuracy;  it will be more difficult to realise;  it will be more compact;  it will take less time to develop;  it will be cheaper to deduce properties.  Design decisions taken early in the design process (based on abstract models) have a large impact on property values. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 10 Example: Switch Fabrics Decision Properties Throughput Average Delay Jitter Quality of Service Design Issues Queues Priorities Backpressure Scheduling Modelling Concepts Modelling Entities Concurrency Communication/Synchronization Time/Stochasticity >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 11 Language Design Considerations/Alternatives Modelling Entities –Separate Data & Control  Autonomous Objects –Structural  Behavioural –... Concurrency –Synchronous  Asynchronous –Inherent to Modelling Entities  Orthogonality Communication/synchronisation –Synchronous  Asynchronous –Buffered  Unbuffered –... Time/stochasticity –Real-time  Discrete-time  Synchrony Hypothesis –Stochastic  Probabilistic  Non-determinism –... > Mathematical semantics Small Expressive Collection of Blending Language Primitives Selection Conflicts Orthogonality POOSL

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 12 The POOSL Language >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 13 Overview of POOSL  POOSL (Parallel Object-Oriented Specification Language) is a formal specification language based on a timed version of process algebra CCS and on the basic concepts of traditional object-oriented programming languages (Smalltalk, Java, C++).  A POOSL specification consists of  A Top-Level Cluster;  Clusters & Cluster Classes;  Process Objects & Process Classes;  Data Objects & Data Classes. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 14 Example: Switch Fabric >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 15 Clusters  Hierarchical structural entities;  Statically interconnected in a topology of channels;  Connect to the channels through private ports;  Consist of process objects and other clusters;  Behave asynchronous concurrent;  Communicate by synchronous message passing;  Organised in cluster classes. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 16 Example: Multistage Switch >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 17 Process objects  Behavioural asynchronous concurrent entities;  Statically interconnected in a topology of channels;  Communicate by synchronous message passing;  Contain data objects;  Compositional behaviour descriptions  Primitive statements: data,time,communication  Constructors: Parallel composition, interrupts, …  Behavioural abstraction: methods;  Are organised in process classes. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 18 Example: Switch >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 19 Process Statements A method body consists of a process statement PS: The execution of PS can result inAction Performance & Time Passage PS ::= | ch!m(DE 1,…,DE n ){DS} synchronous send | delay(DE) delay statement | while E do PS od repetition | DS {DS} data statement | if E then PS 1 else PS 2 fi selection message reception ch?m(p 1,…,p n | DE){DS} | sel PS 1 or … or PS n les choice statement | par PS 1 and … and PS n rap parallel composition | PS 1 interrupt PS 2 interrupt statement | PS 1 abort PS 2 abort statement | [DE]PS guarded command | m(DE 1,…,DE n )(p 1,…,p n ) method call | PS 1 ;PS 2 sequential composition | timestamp x read model time

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 20 Example 1: Intuitive Semantics initialize()() ch!givePosition; delay(3.14); ch?position(point). ch initialize()() ch?givePosition; ch!position(point). instance variable point (10,12) instance variable point givePosition (10,12) position( ) copy > Time: 03.14

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 21 Example 2: initial method startUp of Switch startUp()() outputBufferArray:=new(Array) size(2); outputBufferArray put(1,new(BoundedFIFOBuffer) size(bufferSize)); outputBufferArray put(2,new(BoundedFIFOBuffer) size(bufferSize)); par handleInput1()() and handleInput2()() and handleOutput1()() and handleOutput2()() rap. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 22 Example 3: method handleInput1 of Switch handleInput1()() | cell: Cell | i1?cell(cell | outputBufferArray at(cell destinationPort) isNotFull) {outputBufferArray at(cell destinationPort) put(cell); cell nextDestinationPort}; delay(cellTime); handleInput1()(). >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 23 Example 4: method handleOutput1 of Switch handleOutput1()() [outputBufferArray at(1) isNotEmpty] o1!cell(outputBufferArray at(1) firstElement) {outputBufferArray at(1) removeFirstElement}; delay(cellTime); handleOutput1()(). >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 24 Example 5: Process Class Source >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 25 Data objects  Behavioural sequential entities;  Can be created dynamically;  Communicate by message passing;  Invoke methods upon message reception;  Return results of method invocations to sender;  Are organised in data classes. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 26 Example: Data class Exponential >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 27 > Data Statements and Expressions DS ::= x:=DE | DS 1 ;DS 2 | while DE do DS | if E then DS 1 else DS 2 fi | DE assignment to variable or parameter sequential composition repetition selection data expression A method body consist of a data statement DS : > DE ::= x | new(C) | self | DE m (DE 1,…,DE n ) | -1,0,’a’,’b’,3.14,true,false | nil data object referenced by x newly created data object of data class C data object evaluating this expression method call constants of primitive classes constants undefined data object DE is a data expression, always evaluating to a data object:

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 28 mu rand withParam(m:Real):Exponential mu:=m; rand:=new(RandomGenerator); return(self). Example: Intuitive Semantics Consider the execution of the following statement: exp:=new(Exponential) withParam(3) 3 some Random >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 29 Formal Semantics >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 30 Formal Semantics: Transition System Plotkin-style Structural Operational Interleaving Semantics defines a labelled transition system: Model M can perform action a and then behave as M’ Model M can delay for time t and then behave as M’ > M M’ a Compositional Definition with Axioms and Inference Rules (Mod, Act,T,{ | a  Act},{ | t  T}) at M M’ t delay(t)  t M 1 || M 2 M’ 1 || M’ 2 t M 2 M’ 2 t M 1 M’ 1 t c!m M 2 M’ 2 c?m M 1 || M 2 M’ 1 || M’ 2 

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 31 Action Urgency: Two-Phase Model Asynchronous Execution of Actions Synchronous Passage of Time > [X.Nicollin, J.Sifakis ’91]

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 32 Example: Lossy Channel >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 33 Transition System of a Lossy Channel >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 34 Analysis: Verification Analytical (Exhaustive) –Generate complete transition system using the mathematical semantics –Exhaustive analysis of this transition system –Certain results but only applicable in case of relatively small (finite- state) systems Empirical validation (By Simulation) –Generate one or more execution traces using the mathematical semantics –Analysis of these execution traces –Uncertain results but applicable in case of large and even infinite-state systems >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 35 Analysis: Performance Analytical (Exhaustive) –Generate complete transition system using the mathematical semantics –Exhaustive analysis of this transition system –Compute performance figures using Markov Reward Structures –Certain/precise results but only applicable in case of relatively small finite-state systems Empirical (By Simulation) –Generate one or more execution traces using the mathematical semantics –Analysis these execution traces –Estimate performance figures using statistical methods –Uncertain results but applicable in case of large and even infinite-state systems >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 36 Supporting Tools >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 37 Editing (1) Editing hierarchy and structure...

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 38 Editing (2) Editing behaviour of process and data classes...

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 39 Simulation Executing the behaviour of the model...

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 40 Validation Validating system behaviour...

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 41 Scenarios Using scenarios to focus on specific parts of the model...

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 42 Empirical Performance Estimation > Automatic estimation of performance parameters. With a confidence of 95% the mean throughput is between and

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 43 Conclusions & Further Research >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 44 Conclusion (1) POOSL POOSL is a language developed for system level modelling. It combines a process part based on CCS with a data part based on traditional object-oriented programming languages –Architecture structure and topology is modelled graphically by means of clusters and channels –Complex real-time behaviour is modelled by asynchronous concurrent process objects –Complex dynamic functional behaviour is expressed by (travelling) data objects >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 45 Conclusion (2) Mathematical semantics POOSL is equipped with a complete mathematical semantics enabling analytical and empirical performance evaluation and formal verification Tools Tools are available supporting –modelling, –simulation, –validation –performance analysis. >

Object-Oriented Modelling and Specification using SHE Eindhoven University of Technology, ICS 46 Further Research Performance evaluation –Probabilistic extension of the formal semantics –Model abstraction, analytical techniques based on stochastic processes –Empirical parameter estimation techniques applied to full models Formal (real-time) verification –Model abstraction, exhaustive model checking –Non-exhaustive model checking applied to full models Software synthesis (C++) –Rapid Simulation, Performance Analysis and Verification –Automatic Implementation >