Adult entertainment

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Sign seen in a Singapore shopping center:

 No-Playing

Let us make sure we understand: here children are not allowed, but playing is.

As a consequence such playing must be performed by non-children only. Adults welcome to play!

Maybe it is actually not the intended meaning.  Instead of

(and (not (allowed children)) (allowed playing))

the desired parsing may be

(not (allowed (playing children)))

One hint in favor of this second interpretation is that in practice people seldom put up signs to advertise that something is allowed.

So new-line must be a mere break character equivalent to space, not a semantics-carrying delimiter.

Somewhat reminiscent of eats shoots and leaves. Here it is not even a punctuation mark, just a humble new-line, but its visual effect is strong all the same.

June LASER school, Elba, on Devops, Microservices…

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The 2020 LASER summer school has been announced. It will take place June 1 to 6* , as always in Elba Island, this year with the theme DevOps, Microservices and Software Development for the Age of the Web. The first five speakers are listed on the conference page, with more to come, from both academia and industry.

This is the 16th edition of the school (already) and, as always, rests on the LASER recipe of “Sea, Sun and Software”: densely packed lectures by top experts with the opportunity to enjoy the extraordinary surroundings of the Island of Elba and the Hotel del Golfo’s unique food, beach and facilities, with lots of time devoted to interactions between speakers and attendees.

This year’s theme is devoted to advances in the newest Web technologies and the corresponding software engineering issues and development models.

*Arrival on May 31st, departure on June 7th.

Those were the days

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Earlier this year I was in Sofia for a conference, at the main university (Saint Kliment) which in the entrance hall had an exhibition about its history. There was this student poster and song from I think around 1900:

 

vivat

I like the banner (what do you think?). It even has the correct Latin noun and verb plurals.

Anyone know where to find a university today with that kind of students, that kind of slogan, that kind of attitude and that kind of grammar? Please send me the links.

Formality in requirements: new publication

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The best way to make software requirements precise is to use one of the available “formal” approaches. Many have been proposed; I am not aware of a general survey published so far. Over the past two years, we have been working on a comprehensive survey of the use of formality in requirements, of which we are now releasing a draft. “We” is a joint informal research group from Innopolis University and the University of Toulouse, whose members have been cooperating on requirements issues, resulting in publications listed  under “References” below and in several scientific events.

The survey is still being revised, in particular because it is longer than the page limit of its intended venue (ACM Computing Surveys), and some sections are in need of improvement. We think, however, that the current draft can already provide a solid reference in this fundamental area of software engineering.

The paper covers a broad selection of methods, altogether 22 of them, all the way from completely informal to strictly formal. They are grouped into five categories: natural language, semi-formal, automata- or graph-based, other mathematical frameworks, programming-language based. Examples include SysML, Relax, Statecharts, VDM, Eiffel (as a requirements notation), Event-B, Alloy. For every method, the text proposes a version of a running example (the Landing Gear System, already used in some of our previous publications) expressed in the corresponding notation. It evaluates the methods using a set of carefully defined criteria.

The paper is: Jean-Michel Bruel, Sophie Ébersold, Florian Galinier, Alexandr Naumchev, Manuel Mazzara and Bertrand Meyer: Formality in Software Requirements, draft, November 2019.

The text is available here. Comments on the draft are welcome.

References

Bertrand Meyer, Jean-Michel Bruel, Sophie Ebersold, Florian Galinier and Alexandr Naumchev: Towards an Anatomy of Software Requirements, in TOOLS 2019, pages 10-40, see here (or arXiv version here). I will write a separate blog article about this publication.

Alexandr Naumchev and Bertrand Meyer: Seamless requirements. Computer Languages, Systems & Structures 49, 2017, pages 119-132, available here.

Florian Galinier, Jean-Michel Bruel, Sophie Ebersold and Bertrand Meyer: Seamless Integration of Multirequirements, in Complex Systems, 25th International Requirements Engineering Conference Workshop, IEEE, pages 21-25, 2017, available here.

Alexandr Naumchev, Manuel Mazzara, Bertrand Meyer, Jean-Michel Bruel, Florian Galinier and Sophie Ebersold: A contract-based method to specify stimulus-response requirements, Proceedings of the Institute for System Programming, vol. 29, issue 4, 2017, pp. 39-54. DOI: 10.15514, available here.

Alexandr Naumchev and Bertrand Meyer: Complete Contracts through Specification Drivers., in 10th International Symposium on Theoretical Aspects of Software Engineering (TASE), pages 160-167, 2016, available here.

Alexandr Naumchev, Bertrand Meyer and Víctor Rivera: Unifying Requirements and Code: An Example, in PSI 2015 (Ershov conference, Perspective of System Informatics), pages 233-244, available here.

Publications on CS/SE/informatics education

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Recently I had a need to collect my education-related publications, so I went through my publication list and extracted items devoted to issues of learning computer science (informatics) and software engineering. There turned out to be far more than I expected; I did not think of myself as primarily an education researcher but it seems I am that too. (Not so many research computer scientists take the trouble to publish in SIGCSE, ITiCSE and other top CS education venues.)

Without presuming that the list will be of interest I am reproducing it below for the record. All comes from my publication list here, which contains more information, in particular a descriptive paragraph or two for every single publication.

I have also included PhD theses in education. (Whole list of PhD theses supervised here.)

The topics include among others, in approximate chronological order (although the list below is in the reverse order):

    • Early experience teaching modern programming concepts in both industry and universities.
    • In the nineties, I was full time at Eiffel Software, the development of a general framework for teaching programming. This was written from the safe position of someone in industry advising academic colleagues on what to do (usually the advice goes the other way). I did have, however, the opportunity to practice my preaching in short stints at University of Technology, Sydney and  particularly Monash University. The concept of the Inverted Curriculum (also known as “ Outside-In”) date back to that period, with objects first (actually classes) and contracts first too.
    • When I joined ETH, a general paper on the fundamental goals and concepts of software engineering education, “Software Engineering in the Academy”, published in IEEE Computer.
    • At ETH, putting the Inverted Curriculum in practice, with 14 consecutive sessions of the introductory programming courses for all computer science students, resulting in the Touch of Class textbook and a number of papers coming out of our observations. An estimated 6000 students took the course. A variant of it has also been given several times at Innopolis University.
    • A theory of how to structure knowledge for educational purposes, leading to the notion of “Truc” (Teachable, Reusable Unit of Cognition).
    • The development by Michela Pedroni of the Trucstudio environment, similar in its form to an IDE but devoted, instead of the development of programs, to the visual development of courses, textbooks, curricula etc.
    • Empirical work by Marie-Hélène Ng Cheong Vee (Nienaltowski) and Michela Pedroni on what beginners understand easily, and not, for example according to the phrasing of compiler error messages.
    • Other empirical work, by Michela Pedroni and Manuel Oriol, on the prior knowledge of entering computer science students.
    • The DOSE course (Distributed and Outsourced Software Engineering) ran for several years a student project done by joint student teams from several cooperating universities, including Politecnico di Milano which played a key role along with us. It enabled many empirical studies on the effect on software development of having geographically distributed teams. People who played a major role in this effort are, at ETH, Martin Nordio, Julian Tschannen and Christian Estler and, at Politecnico, Elisabetta di Nitto, Giordano Tamburrelli and Carlo Ghezzi.
    • Several MOOCs, among the first at ETH, on introductory computing and agile methods. They do not appear below because they are not available at the moment on the EdX site (I do not know why and will try to get them reinstated). The key force there was Marco Piccioni. MOOCs are interesting for many reasons; they are a substitute neither for face-to-face teaching nor for textbooks, but an interesting complement offering novel educational possibilities. Thanks to codeboard, see below, our programming MOOCs provide the opportunity to compile and run program directly from the course exercise pages, compare the run’s result to correct answers for prepared tests, and get immediate feedback .
    • A comparative study of teaching effectiveness of two concurrency models, Eiffel SCOOP and JavaThreads (Sebastian Nanz, Michela Pedroni).
    • The development of the EiffelMedia multimedia library at ETH, which served as a basis for dozens of student projects over many years. Credit for both the idea and its realization, including student supervision, goes to Till Bay and Michela Pedroni.
    • The development (Christian Estler with Martin Nordio) of the Codeboard system and site, an advanced system for cloud support to teach programming, enabling students to compile, correct and run programs on the web, with support for various languages. Codeboard is used in the programming MOOCs.
    • A hint system (Paolo Antonucci, Michela Pedroni) to help students get progressive help, as in video games, when they stumble trying to write a program, e.g. with Codeboard.

Supervised PhD theses on education

The following three theses are devoted to educational topics (although many of the  other theses have educational aspects too):

Christian Estler, 2014, Understanding and Improving Collaboration in Distributed Software Development, available here.

Michela Pedroni, 2009, Concepts and Tools for Teaching Programming, available here.

Markus Brändle, 2006: GraphBench: Exploring the Limits of Complexity with Educational Software, available here. (The main supervisor in this case was Jürg Nievergelt.)

MOOCs (Massive Online Open Courses)

Internal MOOCs, and three courses on EdX (links will be added when available):

  • Computing: Art, Magic, Science? Part 1 (CAMS 1), 2013.
  • Computing: Art, Magic, Science? Part 1 (CAMS 2), 2014.
  • Agile Software Development, 2015.

Publications about education

1. Paolo Antonucci, Christian Estler, Durica Nikolic, Marco Piccioni and Bertrand Meyer: An Incremental Hint System For Automated Programming Assignments, in ITiCSE ’15, Proceedings of 2015 ACM Conference on Innovation and Technology in Computer Science Education, 6-8 July 2015, Vilnius, ACM Press, pages 320-325. (The result of a master’s thesis, a system for helping students solve online exercises, through successive hints.) Available here.

2. Jiwon Shin, Andrey Rusakov and Bertrand Meyer: Concurrent Software Engineering and Robotics Education, in 37th International Conference on Software Engineering (ICSE 2015), Florence, May 2015, IEEE Press, pages 370-379. (Describes our innovative Robotics Programming Laboratory course, where students from 3 departments, CS, Mechanical Engineering and Electrical Engineering learned how to program robots.) Available here.

3. Cristina Pereira, Hannes Werthner, Enrico Nardelli and Bertrand Meyer: Informatics Education in Europe: Institutions, Degrees, Students, Positions, Salaries — Key Data 2008-2013, Informatics Europe report, October 2014. (Not a scientific publication but a report. I also collaborated in several other editions of this yearly report series, which I started, from 2011 on. A unique source of information about the state of CS education in Europe.) Available here.

4. (One of the authors of) Informatics education: Europe cannot afford to miss the boat, edited by Walter Gander, joint Informatics Europe and ACM Europe report, April 2013. An influential report which was instrumental in the introduction of computer science in high schools and primary schools in Europe, particularly Switzerland. Emphasized the distinction between “digital literacy” and computer science. Available here.

5. Sebastian Nanz, Faraz Torshizi, Michela Pedroni and Bertrand Meyer: Design of an Empirical Study for Comparing the Usability of Concurrent Programming Languages, in Information and Software Technology Journal Elsevier, volume 55, 2013. (Journal version of conference paper listed next.) Available here.

6. Bertrand Meyer: Knowledgeable beginners, in Communications of the ACM, vol. 55, no. 3, March 2012, pages 10-11. (About a survey of prior knowledge of entering ETH CS students, over many years. Material from tech report below.) Available here.

7. Sebastian Nanz, Faraz Torshizi, Michela Pedroni and Bertrand Meyer: Design of an Empirical Study for Comparing the Usability of Concurrent Programming Languages, in ESEM 2011 (ACM/IEEE International Symposium on Empirical Software Engineering and Measurement), 22-23 September 2011 (best paper award). Reports on a carefully designed empirical study to assess the teachability of various approaches to concurrent programming. Available here.

8. Martin Nordio, H.-Christian Estler, Julian Tschannen, Carlo Ghezzi, Elisabetta Di Nitto and Bertrand Meyer: How do Distribution and Time Zones affect Software Development? A Case Study on Communication, in Proceedings of the 6th International Conference on Global Software Engineering (ICGSE), IEEE Computer Press, 2011, pages 176-184. (A study of the results of our DOSE distributed course, which involved students from different universities in different countries collaborating on a common software development project.) Available here.

9. Martin Nordio, Carlo Ghezzi, Elisabetta Di Nitto, Giordano Tamburrelli, Julian Tschannen, Nazareno Aguirre, Vidya Kulkarni and Bertrand Meyer: Teaching Software Engineering using Globally Distributed Projects: the DOSE course, in Collaborative Teaching of Globally Distributed Software Development – Community Building Workshop (CTGDSD), Hawaii (at ICSE), May 2011. (Part of the experience of our Distributed Outsourced Software Engineering course, taught over many years with colleagues from Politecnico di Milano and elsewhere, see paper in previous entry.) Available here.

10. Bertrand Meyer: From Programming to Software Engineering (slides only), material for education keynote at International Conference on Software Engineering (ICSE 2010), Cape Town, South Africa, May 2010. Available here.

11. Michela Pedroni and Bertrand Meyer: Object-Oriented Modeling of Object-Oriented Concepts, in ISSEP 2010, Fourth International Conference on Informatics in Secondary Schools, Zurich, January 2010, eds. J. Hromkovic, R. Královic, J. Vahrenhold, Lecture Notes in Computer Science 5941, Springer, 2010. Available here.

12. Michela Pedroni, Manuel Oriol and Bertrand Meyer: What Do Beginning CS Majors Know?, ETH Technical Report, 2009. (Unpublished report about the background of 1st-year ETH CS students surveyed over many years. See shorter 2012 CACM version above.) Available here.

13. Bertrand Meyer: Touch of Class: Learning to Program Well Using Object Technology and Design by Contract, Springer, 2009 (also translated into Russian). (Introductory programming textbook, used for many years at ETH Zurich and Innopolis University for the first programming course. The herecontains a long discussion of pedagogical issues of teaching programming and CS.) Book page and text of several chapters here.

14. Michela Pedroni, Manuel Oriol, Lukas Angerer and Bertrand Meyer: Automatic Extraction of Notions from Course Material, in Proceedings of SIGCSE 2008 (39th Technical Symposium on Computer Science Education), Portland (Oregon), 12-15 March 2008, ACM SIGCSE Bulletin, vol. 40, no. 1, ACM Press, 2008, pages 251-255. (As the title indicates, tools for automatic analysis of course material to extract the key pedagogical notions or “Trucs”.) Available here.

15. Marie-Hélène Nienaltowski, Michela Pedroni and Bertrand Meyer: Compiler Error Messages: What Can Help Novices?, in Proceedings of SIGCSE 2008 (39th Technical Symposium on Computer Science Education), Portland (Oregon), Texas, 12-15 March 2008, ACM SIGCSE Bulletin, vol. 40, no. 1, ACM Press, 2008, pages 168-172. (Discusses the results of experiments with different styles of compiler error messages, which can be baffling to beginners, to determine what works best.) Available here.

16. Bertrand Meyer and Marco Piccioni: The Allure and Risks of a Deployable Software Engineering Project: Experiences with Both Local and Distributed Development, in Proceedings of IEEE Conference on Software Engineering & Training (CSEE&T), Charleston (South Carolina), 14-17 April 2008, ed. H. Saiedian, pages 3-16. (Paper associated with a keynote at an SE education conference. See other papers on the DOSE distributed project experience below.) Available here.

17. Till Bay, Michela Pedroni and Bertrand Meyer: By students, for students: a production-quality multimedia library and its application to game-based teaching, in JOT (Journal of Object Technology), vol. 7, no. 1, pages 147-159, January 2008. Available here (PDF) and here (HTML).

18. Marie-Hélène Ng Cheong Vee (Marie-Hélène Nienaltowski), Keith L. Mannock and Bertrand Meyer: Empirical study of novice error paths, Proceedings of workshop on educational data mining at the 8th international conference on intelligent tutoring systems (ITS 2006), 2006, pages 13-20. (An empirical study of the kind of programming mistakes learners make.) Available here.

19. Bertrand Meyer: Testable, Reusable Units of Cognition, in Computer (IEEE), vol. 39, no. 4, April 2006, pages 20-24. (Introduced a general approach for structuring knowledge for teaching purposes: “Trucs”. Served as the basis for some other work listed, in particular papers with Michela Pedroni on the topics of her PhD thesis. Available here.

21. Michela Pedroni and Bertrand Meyer: The Inverted Curriculum in Practice, in Proceedings of SIGCSE 2006, Houston (Texas), 1-5 March 2006, ACM Press, 2006, pages 481-485. (Develops the idea of inverted curriculum which served as the basis for our teaching of programming at ETH, Innopolis etc. and led to the “Touch of Class” textbook.) Available here.

22. Bertrand Meyer: The Outside-In Method of Teaching Introductory Programming, in Perspective of System Informatics, Proceedings of fifth Andrei Ershov Memorial Conference, Akademgorodok, Novosibirsk, 9-12 July 2003, eds. Manfred Broy and Alexandr Zamulin, Lecture Notes in Computer Science 2890, Springer, 2003, pages 66-78. (An early version of the ideas presented in the previous entry.) Available here.

23. Bertrand Meyer: Software Engineering in the Academy, in Computer (IEEE), vol. 34, no. 5, May 2001, pages 28-35. Translations: Russian in Otkrytye Systemy (Open Systems Publications), #07-08-2001, October 2001. (A general discussion of the fundamental concepts to be taught in software engineering. Served as a blueprint for my teaching at ETH.) Available here.

24. Bertrand Meyer: Object-Oriented Software Construction, second edition, Prentice Hall, 1296 pages, January 1997. Translations: Spanish, French Russian, Serbian, Japanese. (Not a publication on education per se but cited here since it is a textbook that has been widely used for teaching and has many comments on pedagogy.)
23. Bertrand Meyer: The Choice for Introductory Software Education, Guest editorial in Journal of Object-Oriented Programming, vol. 7, no. 3, June 1994, page 8. (A discussion of the use of Eiffel for teaching software engineering topics.)

25. Bertrand Meyer, Towards an Object-Oriented Curriculum, in Journal of Object-Oriented Programming, vo. 6, number 2, May 1993, pages 76-81. (Journal version of paper cited next.) Available here.

26. Bertrand Meyer: Towards an Object-Oriented Curriculum, in TOOLS 11, Technology of Object-Oriented Languages and Systems, Santa Barbara, August 1993, eds. Raimund Ege, Madhu Singh and B. Meyer, Prentice Hall 1993, pages 585-594. (Early advocacy for using OO techniques in teaching programming – while I was not in academia. Much of my subsequent educational work relied on those ideas.) Available here.

27. Bertrand Meyer: Object-Oriented Software Construction, Prentice Hall, 592 pages, 1988. (First edition, translated into German, Italian, French, Dutch, Romanian, Chinese. As noted for second edition above, not about education per se, but widely used textbook with pedagogical implications.)

28. Initiation à la programmation en milieu industriel (Teaching Modern Programming Methodology in an Industrial Environment), in RAIRO, série bleue (informatique), vol. 11, no. 1, pages 21-34 1977. (Early paper on teaching advanced programming techniques in industry.) Available here.

29. Claude Kaiser, Bertrand Meyer and Etienne Pichat, L’Enseignement de la Programmation à l’IIE (Teaching Programming at the IIE engineering school), in Zéro-Un Informatique, 1977. (A paper on my first teaching experience barely out of school myself.) Available here.

A theorem of software engineering

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Some of the folk wisdom going around in software engineering, often cluessly repeated for decades, is just wrong.  It can be particularly damaging when it affects key aspects of software development and is contradicted by solid scientific evidence. The present discussion covers a question that meets both of these conditions: whether it makes sense to add staff to a project to shorten its delivery time.

My aim is to popularize a result that is well known in the software engineering literature, going back to the early work of Barry Boehm [1], and explained with great clarity by Steve McConnell in his 2006 book on software cost estimation [2] under the name “Shortest Possible Schedule”. While an empirical rather than a logical result, I believe it deserves to be called a theorem (McConnell stays shy of using the term) because it is as close as we have in the area of software engineering management to a universal property, confirmed by numerous experimental studies.

This article contributes no new concept since McConnell’s chapter 20 says all there is to say about the topic;  my aim is simply to make the Shortest Possible Schedule Theorem better known, in particular to practitioners.

The myth about shortening project times begins with an observation that is clearly correct, at least in an extreme form. Everyone understands that if our project has been evaluated, through accepted cost estimation techniques, to require three developers over a year we cannot magically hire 36 people to complete it in one month. Productivity does not always scale up.

But neither does common sense. Too often the conclusion from the preceding trival observation takes the form of an old  saw, “Brooks’ Law”: adding people to a late project delays it further. The explanation is that the newcomers cost more through communication overhead than they bring through actual contributions. While a few other sayings of Brooks’ Mythical Man-Month have stood the test of time, this one has always struck me as describing, rather than any actual law, a definition of bad management. Of course if you keep haplessly throwing people at deadlines you are just going to add communication problems and make things worse. But if you are a competent manager expanding the team size is one of the tools at your disposal to improve the state of a project, and it would be foolish to deprive yourself of it. A definitive refutation of the supposed law, also by McConnell, was published 20 years ago [3].

For all the criticism it deserves, Brooks’s pronouncement was at least limited in its scope: it addressed addition of staff to a project that is already late. It is even wronger to apply it to the more general issue of cost-estimating and staffing software projects, at any stage of their progress.  Forty-year-old platitudes have even less weight here. As McConnell’s book shows, cost estimation is no longer a black art. It is not an exact science either, but techniques exist for producing solid estimates.

The Shortest Possible Schedule theorem is one of the most interesting results. Much more interesting than Brooks’s purported law, because it is backed by empirical studies (rather than asking us to believe one person’s pithy pronouncement), and instead of just a general negative view it provides a positive result complemented by a limitation of that result; and both are expressed quantitatively.

Figure 1 gives the general idea of the SPS theorem. General idea only; Figure 2 will provide a more precise view.

Image4

Figure 1: General view of the Shortest Possible Schedule theorem.

The  “nominal project” is the result of a cost and schedule estimation yielding the optimum point. The figure and the theorem provide project managers with both a reason to rejoice and a reason to despair:

  • Rejoice: by putting in more money, i.e. more people (in software engineering, project costs are essentially people costs [4]), you can bring the code to fruition faster.
  • Despair: whatever you do, there is a firm limit to the time you can gain: 25%. It seems to be a kind of universal constant of software engineering.

The “despair” part typically gets the most attention at first, since it sets an absolute value on how much money can buy (so to speak) in software: try as hard as you like, you will never get below 75% of the nominal (optimal) value. The “impossible zone” in Figure 1 expresses the fundamental limitation. This negative result is the reasoned and precise modern replacement for the older folk “law”.

The positive part, however, is just as important. A 75%-empty glass is also 25%-full. It may be disappointing for a project manager to realize that no amount of extra manpower will make it possible to guarantee to higher management more than a 25% reduction in time. But it is just as important to know that such a reduction, not at all insignificant, is in fact reachable given the right funding, the right people, the right tools and the right management skills. The last point is critical: money by itself does not suffice, you need management; Brooks’ law, as noted, is mostly an observation of the effects of bad management.

Figure 1 only carries the essential idea, and is not meant to provide precise numerical values. Figure 2, the original figure from McConnell’s book, is. It plots effort against time rather than the reverse but, more importantly, it shows several curves, each corresponding to a published empirical study or cost model surveyed by the book.

Image5

Figure 2: Original illustration of the Shortest Possible Schedule
(figure 2-20 of [3], reproduced with the author’s permission)

On the left of the nominal point, the curves show how, according to each study, increased cost leads to decreased time. They differ on the details: how much the project needs to spend, and which maximal reduction it can achieve. But they all agree on the basic Shortest Possible Schedule result: spending can decrease time, and the maximal reduction will not exceed 25%.

The figure also provides an answer, although a disappointing one, to another question that arises naturally. So far this discussion has assumed that time was the critical resource and that we were prepared to spend more to get a product out sooner. But sometimes it is the other way around: the critical resource is cost, or, concretely, the number of developers. Assume that nominal analysis tells us that the project will take four developers for a year and, correspondingly, cost 600K (choose your currency).  We only have a budget of 400K. Can we spend less by hiring fewer developers, accepting that it will take longer?

On that side, right of the nominal point in Figure 2, McConnell’s survey of surveys shows no consensus. Some studies and models do lead to decreased costs, others suggest that with the increase in time the cost will actually increase too. (Here is my interpretation, based on my experience rather than on any systematic study: you can indeed achieve the original goal with a somewhat smaller team over a longer period; but the effect on the final cost can vary. If the new time is t’= t + T and the new team size s’= s – S, t and s being the nominal values, the cost difference is proportional to  Ts – t’S. It can be positive as well as negative depending on the values of the original t and s and the precise effect of reduced team size on project duration.)

The firm result, however, is the left part of the figure. The Shortest Possible Schedule theorem confirms what good project managers know: you can, within limits, shorten delivery times by bringing all hands on deck. The precise version deserves to be widely known.

References and note

[1] Barry W. Boehm: Software Engineering Economics, Prentice Hall, 1981.

[2] Steve McConnell: Software Estimation ― Demystifying the Black Art, Microsoft Press, 2006.

[3] Steve McConnell: Brooks’ Law Repealed, in IEEE Software, vol. 16, no. 6, pp. 6–8, November-December 1999, available here.

[4] This is the accepted view, even though one might wish that the industry paid more attention to investment in tools in addition to people.

Recycled A version of this article was first published on the Comm. ACM blog under the title The Shortest Possible Schedule Theorem: Yes, You Can Throw Money at Software Deadlines

Software Engineering Education: FISEE coming up

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Over the past few days I have come across several people who told me they want to attend the Frontiers In Software Engineering Education (FISEE) workshop in Villebrumier, 11-13 November, but have not registered yet. If that’s your case please register right now because:

  • The number of spots is limited (it’s a residential event, everyone is hosted onsite, and there is a set number of rooms).
  • We need a preliminary program. The format of the event is flexible, Springer LNCS proceedings come after the meeting, we make room for impromptu presentations and discussions, but still we need a basic framework and we need to finalize it now.

So please go ahead and fill in the registration form.

From the previous posting about FISEE:

The next event at the LASER center in Villebrumier (Toulouse area, Southwest France) is FISEE, Frontiers in Software Engineering Education, see the web site. This small-scale workshop, 11 to 13 November is devoted to what Software Engineering needs, what should be changed, and how new and traditional institutions can adapt to the fast pace of technology.

Workshops at the Villebrumier center favor a friendly, informal and productive interaction between participants, who are all hosted on site. There are no formal submissions, but post-event proceedings will be published as part of the LASER sub-series of Springer Lecture Notes in Computer Science.

Like other events there, FISEE is by invitation; if you are active in the field of software engineering education as an educator, as a potential employer of software engineering graduates, or as a researcher, you can request an invitation by writing to me or one of the other organizers. Attendance is limited to 15-20 participants.

Among already scheduled talks: a keynote by Alexander Tormasov, rector of Innopolis University, and a talk by me on “the 15 concepts of software engineering”.

Software engineering education: Villebrumier LASER center, November

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The next event at the LASER center in Villebrumier (Toulouse area, Southwest France) is FISEE, Frontiers in Software Engineering Education, see the web site. This small-scale workshop, 11 to 13 November is devoted to what Software Engineering needs, what should be changed, and how new and traditional institutions can adapt to the fast pace of technology.

Workshops at the Villebrumier center favor a friendly, informal and productive interaction between participants, who are all hosted on site. There are no formal submissions, but post-event proceedings will be published as part of the LASER sub-series of Springer Lecture Notes in Computer Science.

Like other events there, FISEE is by invitation; if you are active in the field of software engineering education as an educator, as a potential employer of software engineering graduates, or as a researcher, you can request an invitation by writing to me or one of the other organizers. Attendance is limited to 15-20 participants.

Sunrise was foggy today

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Once you have learned the benefits of formally expressing requirements, you keep noticing potential ambiguities and other deficiencies [1] in everyday language. Most such cases are only worth a passing smile, but here’s one that perhaps can serve to illustrate a point with business analysts in your next requirements engineering workshop or with students in your next software engineering lecture.

As a customer of the Swiss telecommunications company Sunrise I receive an occasional “news” email. (As a customer of the Swiss telecommunications company Sunrise I would actually prefer that they spend my money improving  bandwidth,  but let us not digress.) Rather than raw marketing messages these are tips for everyday life, with the presumed intent of ingratiating the populace. For example, today’s message helpfully advises me on how to move house. The admirable advice starts (my translation):

10.7% of all Swiss people relocate every year. Is that your case too for next Autumn?

Actually no, it’s not my case (neither a case of being one of the “Swiss people” nor a case of intending to relocate this Fall). And, ah, the beauty of ridiculously precise statistics! Not 10.8% or 10.6%, mind you, no, 10.7% exactly! But consider the first sentence and think of something similar appearing in a requirements document or user story. Something similar does appear in such documents, all the time, leading to confusions for the programmers interpreting them and to bugs in the resulting systems. Those restless Swiss! Did you know that they include an itchy group, exactly 922,046 people (I will not be out-significant-digited!), who relocate every year?

Do not be silly, I hear you saying. What Sunrise is sharing of its wisdom is that every year a tenth of the Swiss population moves, but not the same tenth every year. Well, OK, maybe I am being silly. But if you think of a programmer reading such a statement about some unfamiliar domain (not one about which we can rely on common sense), the risk of confusion and consequent bugs is serious.

As [1] illustrated in detail, staying within the boundaries of natural language to resolve such possible ambiguities only results in convoluted requirements that make matters worse. The only practical way out is, for delicate system properties, to use precise language, also known technically as “mathematics”.

Here for example a precise formulation of the two possible interpretations removes any doubt. Let Swiss denote the set of Swiss people and  E the number of elements (cardinal) of a finite set E, which we can apply to the example because the set of Swiss people is indeed finite. Let us define slice as the Sunrise-official number of Swiss people relocating yearly, i.e. slice = Swiss ∗ 0.107 (the actual value appeared above). Then one interpretation of the fascinating Sunrise-official fact is:

{s: Swiss | (∀y: Year | s.is_moving (y))} = slice

In words: the cardinal of the set of Swiss people who move every year (i.e., such that for every year y they move during y) is equal to the size of the asserted population subset.

The other possible interpretation, the one we suspect would be officially preferred by the Sunrise powers (any formal-methods fan from Sunrise marketing reading this, please confirm or deny!), is:

∀y: Year | {s: Swiss | s.is_moving (y)} = slice

In words: for any year y, the cardinal of the set of Swiss people who move during y is equal to the size of the asserted subset.

This example is typical of where and why we need mathematics in software requirements. No absolutist stance here, no decree  that everything become formal (mathematical). Natural language is not going into retirement any time soon. But whenever one spots a possible ambiguity or imprecision, the immediate reaction should always be to express the concepts mathematically.

To anyone who has had a successful exposure to formal methods this reaction is automatic. But I keep getting astounded not only by  the total lack of awareness of these simple ideas among the overwhelming majority of software professionals, but also by their absence from the standard curriculum of even top universities. Most students graduate in computer science without ever having heard such a discussion. Where a formal methods course does exist, it is generally as a specialized topic reserved for a small minority, disconnected (as Leslie Lamport has observed [2]) from the standard teaching of programming and software engineering.

In fact all software engineers should possess the ability to go formal when and where needed. That skill is not hard to learn and should be practiced as part of the standard curriculum. Otherwise we keep training the equivalent of electricians rather than electrical engineers, programmers keep making damaging mistakes from misunderstanding ambiguous or inconsistent requirements, and we all keep suffering from buggy programs.

 

References

[1] Self-citation appropriate here: Bertrand Meyer: On Formalism in Specifications, IEEE Software, vol. 3, no. 1, January 1985, pages 6-25, available here.

[2] Leslie Lamport: The Future of Computing: Logic or Biology, text of a talk given at Christian Albrechts University, Kiel on 11 July 2003, available here.