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Software Construction 2013-2014


Link to this page on Github.

This page covers all relevant information concerning the course Software Construction 2013-2014 in the Master Software Engineering, University of Amsterdam.

Primary contact for this course is Tijs van der Storm.

NB We will actively use Twitter during this course, both for Q&A, announcements and during workshops. Please make an account if you haven't already, and start following @SoftwCons!


Lectures and workshops will be from 9:00-11:00 on Wednesday. Lectures will be given by Tijs van der Storm and. Practical course will be on Wednesday from 11:00 to 17:00 and Thursdays the whole day. For details about rooms see datanose.nl. An Cal ICS link can be found here: https://datanose.nl/course_15520.ics.

  • Week 06: Introduction Slides
  • Week 07: Grammars and Parsing Slides
  • Week 08: Domain-Specific Languages Slides
  • Week 09: Examples of "bad" code Slides
  • Week 10: Here's looking at you (Slides lost...)
  • Week 11: Code smell and refactoring dojo (No slides, you can buy the cue cards at QWAN)
  • Week 12: Instead of a Conclusion Slides

Lab assignment:

  • Part 1: February 26th
  • Part 2: March 19th

Reading assignments:

  • Part 1: February 24th
  • Part 2: March 17th

How to pass this course

Required skills:

  • Create good low level designs
  • Produce clean, readable code
  • Reflect upon and argue for/against software construction techniques, patterns, guidelines etc.
  • Assess the quality of code.
  • Select and apply state of the art software construction tools and frameworks.

Required knowledge:

  • Understand basic principles of language implementation (parsing, AST, evaluation, generation)
  • Understand basic aspects of code quality (readability, changeability, extensibility, etc.)
  • Understand encapsulation and modular design

How to pass this course:

  • Be present at all lectures.
  • Get a grade for your code > 5.5
  • Complete the reading assignments (pass/fail)

Required reading

The literature for this course consists of:

  • "Exercises in Programming Style" (Parts I-IV, VI) by Crista Lopes
  • Papers in the Syllabus

The papers will help you improve your programming practice. You are expected to be familiar with their content and apply the techniques where meaningful. If you don't understand the papers, we will not be able to communicate effectively.

Reading assignments

The ReadingAssignments use the examples in the Styles book to test your understanding of the papers in the Syllabus.

The book on programming style is accompanied by a source code repository on Github. If you have coded the example program in a different language than Python in a particular style, you are invited to add the code to our fork of this repository:

NB: the lectures are part of the material for the assignments.

Lab assignment: QL, a DSL for Questionnaires

The lab assignment is based on the Language Workbench Challenge 2013 (LWC'13). The goal of that assignment is to build a DSL for questionnaires (called QL): simple forms with conditions and computed values. See this document for more information.

Check list of required features that you will show that work during grading:

  • Questions are enabled and disabled when different values are entered.

  • The type checker detects:

    • reference to undefined questions
    • duplicate question declarations with different types
    • conditions that are not of the type boolean
    • operands of invalid type to operators
    • references to questions with an undefined value
    • cyclic dependencies between questions
    • duplicate labels (warning)
  • The language supports booleans, integers and string values.

  • Different data types in QL map to different GUI widgets.

Requirements on the implementation:

  • The parser of the DSL is implemented using a grammar-based parser generator.

  • The internal structure of a DSL program is represented using abstract syntax trees.

  • QL programs are executed as GUI programs, not command-line dialogues.

  • QL programs are executed by interpretation, not code generation.

You are encouraged to be creative in terms of libraries or frameworks that you use, but be aware of impending bloat and or a huge number of dependency (all in good measure).

As to programming language, you may choose any of the following languages: Java, C#, Javascript, Haskell, Scala, Clojure, Erlang, Smalltalk, Ruby, Python, Go, Dart, Objective-C, F#. Feel free to take the opportunity to learn a new language, but be aware that your code will be graded as if you're proficient in it and aware of idiomatic coding styles. For Java we provide grammar skeleton code for the parser generators ANTLR, Jacc and Rats! These grammars are incomplete. You may copy one of the skeleton projects and complete it by adding the following features:

  • Syntax for booleans, string literals. Don't forget to take care of keyword reservation: true and false should be parsed as boolean literals, not as identifiers.

  • Add single-line comments (a la Java: //).

  • Add syntax productions for forms, questions, computed questions, types (int, bool, and string) and if-then and if-then-else statements. Use string literals for question labels. See the LWC'13 link above for an example questionnaire.

  • Add tests to check your syntax extensions.

  • Add AST classes for the provided expression categories, and for your syntactic extensions. Make sure the parser creates objects of the appropriate type.

  • Change the start symbol of the parser to parse forms, instead of Expressions.

Note: don't be seduced by the provided example code and start copy-pasting grammar rules around. It is important to have a basic understanding of the parser technology involved. ANTLR, Rats! and Jacc are well-documented on the web. Please use this information to fulfill the above requirements.

Time table for the lab assignment

There are two grading moments of the lab assignment (see above) which correspond to parts of the assignment:

  • Part 1 (Front end): the frontend covers all aspects visible to the users of the DSL: parsing, checking.

  • Part 2 (Back end): the back end includes are aspects related to running QL programs as GUI programs (i.e. the interpreter).

Honor's track

Extensible QL with Object Algebras

Use object algebras to make an extensible implementation. Show that it works by developing a number of language extensions (e.g., unless, repeat, date time values etc.), and operations: pretty print, compile, visualize. This assignment can be done individually or in pairs.

Graphical DSL framework on top of Rascal

The syntax of a DSL does not have to be textual. Sometimes a DSL is better represented with a graphical notation (e.g., state machines, network topologies, class diagrams, Petri nets etc.). The QL language could also be represented graphically. For instance, conditions and questions can be represented as nodes, with the edges between the nodes representing control flow.

In the honor's track you will (as a group) work on providing a graphical layer on top of Rascal using the Eclipse Graphical Editing Framework. The QL language will serve as an example to test the framework. This entails that the backend (code generation, type checking etc.) will be implemented in Rascal. The end goal is to support graphical editors, just like the Rascal IDE currently supports textual editors for DSLs. If the result of this project is of high enough quality we will integrate the code into the main line of the Rascal IDE.

A particular challenge here is how to interface GEF with Rascal. The suggested way to do this is to design a data type that represents graphical models to be displayed and edited using GEF. When the this model changes a value of this data type is handed back to Rascal where domain-specific analyses (type checking etc.) and transformations (e.g. code generation) can be performed. In some cases, notably analyses, some results need to be communicated back to the editor to support services like error marking or refactorings.

Another challenge is how to separate presentation aspects (e.g. box shapes, fonts, line styles etc.) from the semantic and structural aspect of a DSL.

What we look for when grading your code

The following aspects of quality code will be our focus when grading your code:

  • Functionality (e.g., are the requirements implemented)
  • Tests (e.g., presence of meaningful unit tests)
  • Simplicity (absence of code bloat and complexity; YAGNI)
  • Modularity (e.g., encapsulation, class dependencies, package structure)
  • Layout and style (indentation, comments, naming of variables etc.)
  • SOLID principles
  • Sensible (non-)use of design patterns (e.g., Visitor)

More concretely, we ask you to take the following list of advice into consideration.

  • Code quality is of the utmost importance in this course. You will write clean, consistently formatted, concise code. Your naming and indentation convention will be consistent.

  • You show that you master the concepts of encapsulation, modularity and separation of concerns. This should be visible from the code. The structure of the code should show the design.

  • Method and functions should realize a single piece of functionality. You adhere to the Don't Repeat Yourself (DRY) principle.

  • You will select tools and libraries wisely. You can argue why you chose to use a particular artifact.

  • You know your (standard) libraries and APIs. Do not reimplement (simple) functions that can be expected to be in a (standard) library. Especially, do not claim that your version is faster, because: it is irrelevant, and, you're probably wrong. Make the trade-off for reusing a library: do you really need a heavy dependency, for some simple functionality?

  • Test your code using unit tests if this is meaningful. Do not write tests, because your are somehow supposed to. Do not write your own testing framework; use appropriate libraries and/or language features of the platform (e.g., JUnit on Java). Separate test code from main code.

  • Use asserts in the correct way. Asserts are used to document and check assumptions. They are not used for input validation or error handling.

  • Use exception handling wisely. Do not implement your Exception class in a situation where a standard library exception makes perfect sense. Handle exceptions sanely, if possible. Empty catch-blocks are unacceptable 99.9% of the time.

  • Non-constant static variables should be avoided at all cost.

  • If you are forced to need instanceof a lot, you probably have a flaw in your design.

  • You are expected not to indulge in elaborate gold plating. For instance, fancy graphics/user interfaces are not important. YAGNI: You Ain't Gonna Need It. Focus on the simplest thing that could possibly work, first.

  • Do not optimize your code unless you can argue there is a real problem (proven by profiling). Simplicity of the code has priority.

We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil. --Donald Knuth

  • You are not supposed to show off how smart you are.

Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it. --Brian Kernighan

  • You are expected to write comments, only if you need to explain a complicated algorithm or motivate a particular piece of code. Do not engage in obligatory comments. Javadoc (or similar) is ok, but think about the purpose of Javadoc first.

  • It is unacceptable that there are remnants of dead code, commented out sections, or debugging print statements etc. in the code that you will present for grading.

  • You will only present working code for grading. Note: working code implies your project compiles without errors. Additionally, you should use the IDE in the correct way, setup dependencies correctly, provide build-scripts if necessary. If you don't use an IDE, you will use command line build tools or scripts to not repeat yourself.

Please take this advice to heart. It will influence your grade.


Each participant will have to use Github; please make an account if you haven't already. Then send me a note with your Github user name so that I can add you as a team member. After you have commit access, you can clone the following repository and start coding in your own subdirectory.


To start with one of the skeleton projects copy the contents of one of the prototype projects into your private directory. E.g., on Unix-like machines:

cd my-user-dir
cp -r ../prototypes/QLJava/* .

IMPORTANT: You are required to use Github. You should also commit regularly: NO huge final commit before the deadline.

IMPORTANT: You are required to complete the lab assignment individually. We will use clone detection tools to detect plagiarism.

IMPORTANT: The skeleton projects are setup to be used with Eclipse.

IMPORTANT: Remember this is a single, shared Github repository, I expect everyone to act responsibly and try not to break the repository for everyone else, nor mess with anyone else's files.