Presentation by Jason Kealey jkealey@shade University of Ottawa

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Presentation by Jason Kealey

jkealey@shade.caUniversity of Ottawa

Round-trip engineering

2Jason Kealey, jkealey@shade.ca

Round-trip engineering

• Problem statement• Presentation Goals• Tools and techniques

– Implementation level transformations– Design to Implementation and back.– Requirements to Design and back.– Automatic test generation

• Conclusion

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Problem Statement

4Jason Kealey, jkealey@shade.ca

Problem Statement

• First year:– Introduction to Java and UML Class Diagrams

• Second year:– Overview of other UML diagrams (architectural,

sequence, activity, etc.)

• Third year:– Design patterns, more advanced OOAD– Functional (Use cases) and non-functional requirements

• Fourth year:– Software development process– Software engineering capstone project

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Problem Statement

• Once you have gone through the SEG program, you know you have to think before coding (UML modeling), so you do it. – But you know you can’t plan everything ahead of time, so

you get to work with only a partial design. And that’s OK!

• However, once you hit implementation, how many of you actually go and review your requirements, use cases or software architecture?

• In other words, you learned what you should be doing, but how many of you are actually doing it?

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Problem Statement

• How are you going to write conformance tests from your requirements if they aren’t even up to date anymore?

• You probably can’t refer to the documentation to write your system tests either!

• What happens when someone else works on the project? School: it doesn’t happen. Work: precious resources wasted due to difficult maintenance.

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Problem Statement

• Why aren’t you keep your earlier software artefacts up to date?– Time pressure (especially true in industry)– Duplication of effort– Requires too much discipline– Laziness– Other people don’t update, so my updates are worthless.– Use of waterfall

• Who cares about tests anyways? • We only test during the “testing phase” – but we’re already late

on delivery, so we don’t test at all.

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Problem Statement

• Some of the above reasons are simply bad, but others are justifiable.

• Duplication of effort: – Artefact maintenance is redundant– Artefact maintenance is error-prone

• Developers don’t see the added-value immediately and can’t verify the correctness of their modifications as easily as code.

• What does that tell me? • Redundant tasks deserve to be automated.

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Solution

10Jason Kealey, jkealey@shade.ca

Solution

• Automatic generation of software engineering artefacts from more abstract ones. (forward engineering)

• Inference of abstract artefacts from concrete ones (reverse engineering)

• Automatic synchronization of artefacts from requirements, to design, to code, to tests. – Round-trip engineering– Refactoring of any artefact impacts others. Changes are

propagated automatically.

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Solution

• This is all well and nice, but the current state of software engineering is far from this utopia.

• However, some interesting tools and techniques currently exist to bridge the gap between the various software development artefacts.

• Transformations are easier to do on concrete artefacts. Hence, the most advanced tools work close to the implementation level.

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Goals

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Goals

• Today’s talk aims at presenting a few interesting tools and techniques that are useful to the time-pressured software engineer.

• Many tools are imperfect, but you could get to work on them! (Open source projects, graduate studies)

• The discussion aims at staying close to concrete details so that the tools are useful in real-world situations. However, the closer you are to high-level requirements, the transformations are unavoidably more abstract.

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Implementation-level transformations

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Implementation-level transformations

• A common task in today’s business world is to create data-driven web applications.

• Many different DBMSs exist for persistence

• Various programming/scripting languages are used.

• Possibility to interweave SQL code with business logic and HTML output.

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Implementation-level transformations

• This is bad for many reasons.– Maintainability– Extensibility– Testability

• By keeping the model, the view and the business logic intertwined in the same code, it becomes especially hard to evaluate the impact of database changes on the project.

• Solution: split into a three-tiered application. Manipulate objects instead of DataTables.

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Implementation-level transformations

• Our old friend redundancy comes over and points out that creating classes that correspond to database tables is long and error-prone.

• Persisting the modified elements back into the database is also redundant.

• Solution: Automation! (you had to see this coming)

• Discussion of how to map– http://www.agiledata.org/essays/mappingObjects.html

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Implementation-level transformations

• Let us focus on Hibernate, for this talk.• The basic benefit of using Hibernate is that it will

automate the persistence of Java objects to relational databases.

1. Java Classes (Objects, attributes)

2. Hibernate mapping file

3. Database (Tables, columns, rows)

• Creating these manually is still tedious, we can obtain even more automation.

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Implementation-level transformations

• Hibernate (forward engineering):– Given Java classes (with annotations), it can generate

both the mappings and the database.• Hibernate (reverse engineering):

– Given a database, it can generate both the mappings and the Java classes.

• Hibernate Synchronizer (plug-in):– Given changes to mappings, it reflect those changes to

the code.• Depending on the context (Greenfield project

versus software evolution), all transformations are useful.

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Implementation-level transformations

• Tools:– Hibernate, NHibernate

• http://www.hibernate.org

– Middlegen• http://boss.bekk.no/boss/middlegen/

– Gentle.NET • http://www.mertner.com/confluence/

– J2EE Container managed persistence• http://java.sun.com/developer/technicalArticles/ebeans/EJB20

CMP/

– Object Databases• http://en.wikipedia.org/wiki/List_of_object-

oriented_database_management_systems

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Implementation-level transformations

• Another common problem is writing parsers for particular formats (file formats or pseudo-code for example).

• You’ve used tools to generate C-based parsers from BNF grammars in SEG2101.

– Lex/Yacc – Flex/Bison

• The basic concept is to define the abstract grammar and have the parser/interpreter code generated automatically. This code can either be used directly or integrated into other projects.

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Implementation-level transformations

• These exist for other languages as well. – JavaCC/JJTree, ANTLR, SableCC

– Many of these can generate code in multiple languages (Java, C++, C#, Python, etc.).

– http://en.wikipedia.org/wiki/List_of_compiler-compilers

• Before writing your own parser for a known language, you should try to find its BNF grammar. For example, JavaCC’s grammar repository provides grammars for Java, SQL,C/C++, Rational Rose Petal files, RTF, VHDL, Visual Basic, etc.

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Design to implementation

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Design to implementation

• In a previous tutorial, I mentioned the Eclipse Modeling Framework (EMF) as a code generator. The basic concept is simple. Given a UML Class diagram, generate equivalent Java code.

• Overview: – http://www.eclipse.org/emf/docs.php?doc=references/overview/EMF.html

• Features:– Can import from XMI, XSD, Annotated Java– Conditional re-generation– Can generate simple Eclipse-based editors

• Runtime features:– Integrated two-way reference management– Great notification mechanism– Automated persistence to XML (XMI).– Reflective API

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Design to implementation

• Because EMF is so simple to use, work you put into your model is quickly propagated to your implementation and the model is always in synch.

• Other tools exist to achieve the same goal, such as ArgoUML. Because code generation is not a difficult task, generators exist for many different languages.

• EMF is tremendously useful but it does not generate code representing the behaviour of the application.

• I strongly recommend that the underlying model layer in an MVC architecture be at least partially generated.

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Design to implementation

• One can model the behavioural aspects using state machines, for example. However, I have not played with any tools which generate code from these.

• If we want to generate more than just the model layer, we can investigate domain-specific generators. By defining fine-grained models, we can generate much more.

• For example, the Eclipse Generic Modeling Environment generates graphical editors based on EMF and GEF from models.

– http://wiki.eclipse.org/index.php/GMF_Tutorial

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Design to implementation

• Many other alternatives exist to generate graphical editors for custom notations.

– Generic Modeling Environment (GME)– Xactium’s XMF-Mosaic– Telelogic Tau G2 (for UML profiles)– Rational Software Architect (for UML profiles)

• If you work in an environment where you are constantly producing similar software (simple websites for example), you development process could be improved by writing your own code generator from a custom notation.

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Implementation to design

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Implementation to design

• Many tools offer the possibility to reverse engineer UML class diagrams from code, but none have impressed me enough to be worth presenting here.

• One can also reverse engineer other UML diagrams such as state machines from code.

• Work has been done in reverse engineering behavioural models from execution traces.

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Requirements to design

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Requirements to design

• There is lots of research in this area but only one that I wish to present in detail: Aspects.

• Gunter Mussbacher has provided an excerpt of a talk he made this summer for your perusal.

• The talk follows the methodology presented by Ivar Jacobson in his book which recommends deriving Aspects from Use Cases.

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Requirements to design

• An example Aspect (AspectJ notation):– http://www.eclipse.org/aspectj/doc/released/progguide/

language-anatomy.html#an-example-aspect

• Aspect-Oriented Development is gaining steam. Furthermore, it is not limited to Java: most major languages have their own implementation.

– http://en.wikipedia.org/wiki/Aspect-oriented_programming#Implementations

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Requirements to design

• There are transformations that generate an high-level design from use cases. Notably, UCEd is a tool made by Stéphane Somé and his students that can generate finite state machines from use cases.

• The GUI is not wonderful, but I mention it here because I wrote a transformation from UCEd use cases to Use Case Maps

• The tool I worked on for my capstone project is useful to evaluate candidate architectures. The transformation is not automated, however.

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Design to requirements

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Design to requirements

• Other than Aspects which I mentioned previously, I don’t have interesting tools to present for this.

• There is lots of research in this domain but many introduce new notations or impose methodologies to recover requirements from the design.

• Textual requirements are very hard to reverse engineer, but some things are easier:

– High-level use cases from acceptance tests

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Automatic test generation

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Automatic test generation

• Acceptance tests– If requirements are defined with enough formalism

(using pre-post conditions) and traceability is kept onto the design/code, it may be possible to automatically generate these. No tools to recommend.

– You can ease the pain of writing these tests manually by using tools such as FitNesse. • http://fitnesse.org/FitNesse.TwoMinuteExample

– Tools exist to automate UI testing, for both web-based UIs and conventional applications. The most sophisticated tools can track controls even if they move in the user interface. (Better than reproducing pixel-precise clicks.)

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Automatic test generation

• System Tests– Annotations and OCLs can be used to automate some tests, or at

least their infrastructure.• http://www.eclipse.org/emf/docs.php?doc=references/overview/EMF.Validation.html

• Unit tests– Annotations can also be used to automatically test an

implementation in the context of design by contract.• http://www.cs.iastate.edu/~leavens/JML/

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Conclusion

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Conclusion

• There are lots of tools out there to help facilitate the developer’s life.

• No single person has in-depth experience with all of these tools, that is why sharing your experiences is a important aspect of the software engineering practice.