A Lightweight Approach for the Semantic Validation of ... fileMBT 2008 - Fourth Workshop on Model-Based Testing March 30, 2008, Budapest, Hungary Satellite event of ETAPS 2008 A Lightweight

MBT 2008 MBT 2008 -- Fourth Workshop on ModelFourth Workshop on Model--Based Testing Based Testing March 30, 2008, Budapest, HungaryMarch 30, 2008, Budapest, Hungary

Satellite event of Satellite event of ETAPS 2008ETAPS 2008

A Lightweight Approach for the Semantic Validation of Model Refinements

LIFIA – Faculty of Informatics, University of La Plata Buenos Aires, Argentina

http://sol.info.unlp.edu.ar/eclipse

Claudia Pons and Diego Garcia

2/MBT at ETAPS - Budapest, Hungary - March 30th, 2008

This work is about…

Test Cases


The NEW paradigm

Model Driven Engineering

• Platform Independent Model (PIM)• Platform Specific Model (PSM)• Transformation languages (QVT)

A new problem:

How to test and/or verify

transformations?


The “NEW” paradigm ?Model-Driven Engineering

Specification

Refinementsteps

Refinement is the process of developing a more detailed design or

implementation from an abstract specification through a sequence of

mathematically-based steps that maintain correctness with respect to the

original specification.

Refinement captures the essential relationship between specification and

implementation.

Edsger W. Dijkstra, A Discipline of Programming. Prentice Hall Series in

Automatic Computation. New York, 1976

Software System


How to verify transformation (i.e., refinement)?Model-Driven Engineering

We have two alternatives:

MOF/UML/OCL Language Formal

Language

Translation of refinements

Promotion of refinements

Refinement in MOF/UML/OCL

Well founded refinement

structures in Z

Inspiration source for…

Our proposal:


SyntaxRefinements in Z


SemanticsRefinements in Z

Downward simulation rules:

Initialization:

Applicability:

Correctness:

A specificationsimulation of If:

is a downward


Syntax and semanticsThe standard modeling language UML provides an artifact named Abstractionto explicitly specify abstraction/refinement relationship between model elements.

Refinements in UML

Only syntax.No formal semantics is provided!

a.capacity = c.seat ->size() anda.reservedSeats=c.seat->select(s|s.reserved)->size()


A lightweight strategyEncoding downwards simulation in OCL.

Checking refinements in UML

(1) The Retrieve relation:

Context c:FlightC def: abs(): FlightA =

FlightA.allInstances() -> select ( a | a.capacity = c.seat -> size() anda.reservedSeats = c.seat -> select (s | s.reserved ) -> size()

) -> any()




(2) The Initialization condition:

is expressed in OCL by means of the following constraint,

The following initialization condition for Z specifications,

FlightC.allInstances()->forAll(c|c.isInit()implies a.isInit())




(3) The applicability condition:


The following applicability condition for Z specifications,

FlightC.allInstances()-> forAll(c|a.preReserve() implies c.preReserve())




(4) The correctness condition:


The following correctness condition for Z specifications,

FlightC.allInstances()-> forAll( c, c_post| (a.preReserve()and c_post.hasReturnedReserve(c))implies a_post.hasReturnedReserve(a) )


Tool supportChecking Refinements in UML

ePLATERO: EclipsePLuginAssisting Traceability in an Environment withRefinement Orientation

ePLATERO is a CASE tool for supporting refinement-driven and model-driven software development, using graphical notations with formal foundation.

ePLATERO is a plug-in for the Eclipse platform.


PLATERO’s Functionalitymodel editor ••Creation of UML artifacts with OCL constraintsCreation of UML artifacts with OCL constraints

••Visualization of errors of wellVisualization of errors of well--formedness.formedness.•• Specification of Abstraction artifact whit its corresponding abstraction mapping.


PLATERO’s Functionalitymodel editor (OCL invariants, pre and post conditions)


PLATERO’s Functionalityrefinement evaluation (OCL condition generation)


PLATERO’s Functionalityrefinement evaluation (OCL condition generation)


But, this is not enough…


The micro worlds strategyEvaluation of OCL conditions

To make the evaluation of refinement conditions viable, the technique of micro-worlds of software is applied:

•defining a finite bound on the size of instances;

•checking whether all instances of that size satisfy the property under consideration.

Positive answer(confidence)

Negative answer(refutation)


Improving the micro-worlds by applyingtesting techniques

Evaluation of OCL conditions

•Select only a finite amount of representative micro-worlds:• determine relevant values for the properties (attributes and multiplicities) of objects building up each micro-world;

The category-partition method

Partitions:FlightC::canceled {true}, {false} FlightC::#seat {0}, {1..299}, {300} Seat::reserved {true}, {false} Seat::number {0}, {1..299}, {300} Additional Constraints:context FlightA inv: self.reservedSeats

<= self.capacity


Improving the micro-worlds by applyingtesting techniques

• Adequacy criterions are defined.• Cost considerations and available resources determine the selection of one criterion over another.

OneRangeCombinationeach range of each property is covered at least once.

AllRangesCombinationone object for each possible combination of ranges for all the properties of a class.

the Strategy design pattern to facilitate adding other strategies

Evaluation of OCL conditions


PLATERO’s Functionalityrefinement evaluation (micro-world generation)


PLATERO’s Functionalityrefinement evaluation (micro-world size and range combination strategy)


PLATERO’s Functionalityrefinement evaluation (micro-world visualization)


PLATERO’s Functionalityrefinement evaluation (positive answer)


Experimental results

020406080

100

size 5 size 10 Size 15

ePlatero oneRangeePlatero AllRangeAlloy

0

2000

4000

6000

8000

10000

Size 5 Size 10 Size 15

ePlatero OneRangeePlatero AllRangeAlloy

Table 1. average evaluation costs according to the size of the micro-worlds

Table 2. percentage of correct responses according to the size of the micro-world


Conclusions •Transformations should be formally verified - to guarantee

correctness

• Verification requires the application of formal modeling

languages - complex , rarely used in practice.

•We developed an automatic method for creating refinement

conditions for UML models, written in the standard and well-

accepted OCL language.

•We adapted a strategy for reducing the search scope in order

to make the evaluation of refinement conditions feasible.

•This is a lightweight approach that avoids the use of

mathematical languages and tools.

Documents

A Lightweight Approach for the Semantic Validation of ... fileMBT 2008 - Fourth Workshop on Model-Based Testing March 30, 2008, Budapest, Hungary Satellite event of ETAPS 2008 A Lightweight