Research in Programming Languages
Is there still research to be done in Programming Languages? This essay touches both on the topic of programming languages and on the nature of research work. I am mostly concerned in analyzing this question in the context of Academia, i.e. within the expectations of academic programs and research funding agencies that support research work in the STEM disciplines (Science, Technology, Engineering, and Mathematics). This is not the only possible perspective, but it is the one I am taking here.
PLs are dear to my heart, and a considerable chunk of my career was made in that area. As a designer, there is something fundamentally interesting in designing a language of any kind. It’s even more interesting and gratifying when people actually start exercising those languages to create non-trivial software systems. As a user, I love to use programming languages that I haven’t used before, even when the languages in question make me curse every other line.
But the truth of the matter is that ever since I finished my Ph.D. in the late 90s, and especially since I joined the ranks of Academia, I have been having a hard time convincing myself that research in PLs is a worthy endeavor. I feel really bad about my rational arguments against it, though. Hence this essay. Perhaps by the time I am done with it I will have come to terms with this dilemma.
Back in the 50s, 60s and 70s, programming languages were a BigDeal, with large investments, upfront planning, and big drama on standardization committees (Ada was the epitome of that model). Things have changed dramatically during the 80s. Since the 90s, a considerable percentage of new languages that ended up being very popular were designed by lone programmers, some of them kids with no research inclination, some as a side hobby, and without any grand goal other than either making some routine activities easier or for plain hacking fun. Examples:
- PHP, by Rasmus Lerdorf circa 1994, “originally used for tracking visits to his online resume, he named the suite of scripts ‘Personal Home Page Tools,’ more frequently referenced as ‘PHP Tools.’ ”  PHP is a marvel of how a horrible language can become the foundation of large numbers of applications… for a second time! Worse is Better redux. According one informal but interesting survey, PHP is now the 4th most popular programming language out there, losing only to C, Java and C++.
- Python, by Guido van Rossum circa 1990, “I was looking for a ‘hobby’ programming project that would keep me occupied during the week around Christmas.”  Python comes at #6, and its strong adoption by scientific computing communities is well know.
- Ruby, by Yukihiro “Matz” Matsumoto circa 1994, “I wanted a scripting language that was more powerful than Perl, and more object-oriented than Python. That’s why I decided to design my own language.”  At #10 in that survey.
Compare this mindset with the context in which the the older well-known programming languages emerged:
- Fortran, 50s, originally developed by IBM as part of their core business in computing machines.
- Cobol, late 50s, designed by a large committee from the onset, sponsored by the DoD.
- Lisp, late 50s, main project occupying 2 professors at MIT and their students, with the grand goal of producing an algebraic list processing language for artificial intelligence work, also funded by the DoD.
- C, early 70s, part of the large investment that Bell Labs was doing in the development of Unix.
- Smalltalk, early 70s, part of a large investment that Xerox did in “inventing the future” of computers.
There is a lot of fun in designing new languages, but this fun is not an exclusive right of researchers with, or working towards, Ph.Ds. Given all the knowledge about programming languages these days, anyone can do it. And many do. And here’s the first itchy point: there appears to be no correlation between the success of a programming language and its emergence in the form of someone’s doctoral or post-doctoral work. This bothers me a lot, as an academic. It appears that deep thoughts, consistency, rigor and all other things we value as scientists aren’t that important for mass adoption of programming languages. But then again, I’m not the first to say it. It’s just that this phenomenon is hard to digest, and if you really grasp it, it has tremendous consequences. If people (the potential users) don’t care about conceptual consistency, why do we keep on trying to achieve that?
Also to be fair, not all languages designed in the 90s and later started as side projects. For example, Java was a relatively large investment by Sun Microsystems. So was .NET later by Microsoft.
And, finally, all of these new languages, even when created over a week as someone’s pet project, sit on the shoulders of all things that existed before. This leads me to the second itch: one striking commonality in all modern programming languages, especially the popular ones, is how little innovation there is in them! Without exception, including the languages developed in research groups, they all feel like mashups of concepts that already existed in programming languages in 1979, wrapped up in their own idiosyncratic syntax. (I lied: exceptions go to aspects and monads both of which came in the 90s)
So one pertinent question is: given that not much seems to have emerged since 1979 (that’s 30+ years!), is there still anything to innovate in programming languages? Or have we reached the asymptotic plateau of innovation in this area?
I need to make an important detour here on the nature of research.
Perhaps I’m completely off; perhaps producing innovative new software is not a goal of [STEM] research. Under this approach, any software work is dismissed from STEM pursuits, unless it is necessary for some specific goal — like if you want to study some far-off galaxy and you need an IT infrastructure to collect the data and make simulations (S for Science); or if you need some glue code for piecing existing systems together (T for Technology); or if you need to improve the performance of something that already exists (E for Engineering); or if you are a working on some Mathematical model of computation and want to make your ideas come to life in the form of a language (M for Mathematics). This is an extreme submissive view of software systems, one that places software in the back sit of STEM and that denies the existence of value in research in/by software itself. If we want to lead something on our own, let’s just… do empirical studies of technology or become biologists/physicists/chemists/mathematicians or make existing things perform better or do theoretical/statistical models of universes that already exist or that are created by others. Right?
I confess I have a dysfunctional relationship with this idea. Personally, I can’t be happy without creating software things, but I have been able to make my scientist-self function both as a cold-minded analyst and, at times, as an expert passenger in someone else’s research project. The design work, for me, has moved to sabbatical time, evenings and weekends; I don’t publish it [much] other than the code itself and some informal descriptions. And yet, I loathe this situation.
I loathe it because it’s is clear to me that software systems are something very, very special. Software revolutionized everything in unexpected ways, including the methods and practices that our esteemed colleagues in the “hard” sciences hold near and dear for a very long time. The evolution of information technology in the past 60 years has been _way_ off from what our colleagues thought they needed. Over and over again, software systems have been created that weren’t part of any scientific project, as such, and that ended up playing a central role in Science. Instead of trying to mimic our colleagues’ traditional practices, “computer scientists” ought to be showing the way to a new kind of science — maybe that new kind of science or that one or maybe something else. I dare to suggest that the something else is related to the design of things that have software in them. It should not be called Science. It is a bit like Engineering, but it’s not it either because we’re not dealing [just] with physical things. Technology doesn’t cut it either. It needs a new name, something that denotes “the design of things with software in them.” I will call it Design for short, even though that word is so abused that it has lost its meaning.
Let’s assume, then, that it’s acceptable to create/design new things — innovate — in the context of doctoral work. Now comes the real hard question.
If anyone — researchers, engineers, talented kids, summer interns — can design and implement programming languages, what are the actual hard goals that doctoral research work in programming languages seeks that distinguishes it from what anyone can do?
Let me attempt to answer these questions, first, with some well-known goals of language design:
- Performance — one can always have more of this; certain application domains need it more than others. This usually involves having to come up with interesting data structures and algorithms for the implementation of PLs that weren’t easy to devise.
- Human Productivity — one can always want more of this. There is no ending to trying to make development activities easier/faster.
- Verifiability — in some domains this is important.
There are other goals, but they are second-order. For example, languages may also need to catch up with innovations in hardware design — multi-core comes to mind. This is a second-order goal, the real goal behind it is to increase performance by taking advantage of potentially higher-performing hardware architectures.
In other words, someone wanting to do doctoral research work in programming languages ought to have one or more of these goals in mind, and — very important — ought to be ready to demonstrate how his/her ideas meet those goals. If you tell me that your language makes something run faster, consume less energy, makes some task easier or results in programs with less bugs, the scientist in me demands that you show me the data that supports such claims.
A lot of research activity in programming languages falls under the performance goal, the Engineering side of things. I think everyone in our field understands what this entails, and is able to differentiate good work from bad work under that goal. But a considerable amount of research activities in programming languages invoke the human productivity argument; entire sub-fields have emerged focusing on the engineering of languages that are believed to increase human productivity. So I’m going to focus on the human productivity goal. The human productivity argument touches on the core of what attracts most of us to creating things: having a direct positive effect on other people. It has been carelessly invoked since the beginning of Computer Science. (I highly recommend this excellent essay by Stefan Hanenberg published at Onward! 2010 with a critique of software science’s neglect of human factors)
Unfortunately, this argument is the hardest to defend. In fact, I am yet to see the first study that convincingly demonstrates that a programming language, or a certain feature of programming languages, makes software development a more productive process. If you know of such study, please point me to it. I have seen many observational studies and controlled experiments that try to do it [5, 6, 7, 8, 9, 10, among many]. I think those studies are really important, there ought to be more of them, but they are always very difficult to do [well]. Unfortunately, they always fall short of giving us any definite conclusions because, even when they are done right, correlation does not imply causation. Hence the never-ending ping-pong between studies that focus on the same thing and seem to reach opposite conclusions, best known in the health sciences. We are starting to see that ping-pong in software science too, for example 7 vs 9. But at least these studies show some correlations, or lack thereof, given specific experimental conditions, and they open the healthy discussion about what conditions should be used in order to get meaningful results.
I have seen even more research and informal articles about programming languages that claim benefits to human productivity without providing any evidence for it whatsoever, other than the authors’ or the community’s intuition, at best based on rational deductions from abstract beliefs that have never been empirically verified. Here is one that surprised me because I have the highest respect for the academic soundness of Haskell. Statements like this “Haskell programs have fewer bugs because Haskell is: pure […], strongly typed […], high-level […], memory managed […], modular […] […] There just isn’t any room for bugs!” are nothing but wishful thinking. Without the data to support this claim, this statement is deceptive; while it can be made informally in a blog post designed to evangelize the crowd, it definitely should not be made in the context of doctoral work unless that work provides solid evidence for such a strong statement.
That article is not an outlier. The Internets are full of articles claiming improved software development productivity for just about every other language. No evidence is ever provided, the argumentation is always either (a) deducted from principles that are supposed to be true but that have never been verified, or (b) extrapolated from ad-hoc, highly biased, severely skewed personal experiences.
This is the main reason why I stopped doing research in Programming Languages in any official capacity. Back when I was one of the main evangelists for AOP I realized at some point that I had crossed the line to saying things for which I had very little evidence. I was simply… evangelizing, i.e. convincing others of an idea that I believed strongly. At some point I felt I needed empirical evidence for what I was saying. But providing evidence for the human productivity argument is damn hard! My scientist self cannot lead doctoral students into that trap, a trap that I know too well.
Moreover, designing and executing the experiments that lead to uncovering such evidence requires a lot of time and a whole other set of skills that have absolutely nothing to do with the time and skills for actually designing programming languages. We need to learn the methods that experimental psychologists use. And, in the end of all that work, we will be lucky if we unveil correlations but we will not be able to draw any definite conclusions, which is… depressing.
But without empirical evidence of any kind, and from a scientific perspective, unsubstantiated claims pertaining to, say, Haskell or AspectJ (which are mostly developed and used by academics and have been the topic of many PhD dissertations) are as good as unsubstantiated claims pertaining to, say, PHP (which is mostly developed and used by non-academics). The PHP community is actually very honest when it comes to stating the benefits of using the language. For example, here is an honest-to-god set of reasons for using PHP. Notice that there are no claims whatsoever about PHP leading to less bugs or higher programmer productivity (as if anyone would dare to state that!); they’re just pragmatic reasons. (Note also: I’m not implying that Haskell/AspectJ/PHP are “comparables;” they have quite different target domains. I’m just comparing the narratives surrounding those languages, the “stories” that the communities tell within themselves and to others)
OK, now that I made 823 enemies by pointing out that the claims about human productivity surrounding languages that have emerged in academic communities — and therefore ought to know better — are unsubstantiated, PLUS 865 enemies by saying that empirical user studies are inconclusive and depressing… let me try to turn my argument around.
Is the high bar of scientific evidence killing innovation in programming languages? Is this what’s causing the asymptotic behavior? It certainly is what’s keeping me away from that topic, but I’m just a grain of sand. What about the work of many who propose intriguing new design ideas that are then shot down in peer-review committees because of the lack of evidence?
This ties back to my detour on the nature of research.
<Join Detour> Design experimentation vs. Scientific evidence
So, we’re back to whether design innovation per se is an admissible first-order goal of doctoral work or not. And now that question is joined by a counterpart: is the provision of scientific evidence really required for doctoral work in programming languages?
If what we have in hand is not Science, we need to be careful not to blindly adopt methods that work well for Science, because that may kill the essence of our discipline. In my view, that essence has been the radical, fast-paced, off the mark design experimentation enabled by software. This rush is fairly incompatible with the need to provide scientific evidence for the design “hopes.”
I’ll try a parallel: drug design, the modern-day equivalent of alchemy. In terms of research it is similar to software: partly based on rigor, partly on intuitions, and now also on automated tools that simply perform an enormous amount of logical combinations of molecules and determine some objective function. When it comes to deployment, whoever is driving that work better put in place a plan for actually testing the theoretical expectations in the context of actual people. Does the drug really do what it is supposed to do without any harmful side effects? We require scientific evidence for the claimed value of experimental drugs. Should we require scientific evidence for the value of experimental software?
The parallel diverges significantly with respect to the consequences of failure. A failure in drug design experimentation may lead to people dying or getting even more sick. A failure in software design experimentation is only a big deal if the experiment had a huge investment from the beginning and/or pertains to safety-critical systems. There are still some projects like that, and for those, seeking solid evidence of their benefits before deploying the production version of the experiment is a good thing. But not all software systems are like that. Therefore the burden of scientific evidence may be too much to bear. It is also often the case that over time, the enormous amount of testing by real use is enough to provide assurances of all kinds.
One good example of design experimentation being at odds with scientific evidence is the proposal that Tim Berners-Lee made to CERN regarding the implementation of the hypertext system that became the Web. Nowhere in that proposal do we find a plan for verification of claims. That’s just a solid good proposal for an intriguing “linked information system.” I can imagine TB-L’s manager thinking: “hmm, ok, this is intriguing, he’s a smart guy, he’s not asking that many resources, let’s have him do it and see what comes of it. If nothing comes of it, no big deal.” Had TB-L have to devise a scientific or engineering assessment plan for that system beyond “in the second phase, we’ll install it on many machines” maybe the world would be very different today, because he might have gotten caught in the black hole of trying to find quantifiable evidence for something that didn’t need that kind of validation.
Granted, this was not a doctoral topic proposal; it was a proposal for the design and implementation of a very concrete system with software in it, one that (1) clearly identified the problem, (2) built on previous ideas, including the author’s own experience, (3) had some intriguing insights in it, (4) stated expected benefits and potential applications — down to the prediction of search engines and graph-based data analysis. Should a proposal like TB-L’s be rejected if it were to be a doctoral topic proposal? When is an unproven design idea doctoral material and other isn’t? If we are to accept design ideas without validation plans as doctoral material, how do we assess them?
Towards the discipline of Design
In order to do experimental design research AND be scientifically honest at the same time, one needs to let go of claims altogether. In that dreadful part of a topic proposal where the committee asks the student “what are your claims?” the student should probably answer “none of interest.” In experimental design research, one can have hopes or expectations about the effects of the system, and those must be clearly articulated, but very few certainties will likely come out of such type of work. And that’s ok! It’s very important to be honest. For example, it’s not ok to claim “my language produces bug-free programs” and then defend this with a deductive argument based on unproven assumptions; but it’s ok to state “I expect that my language produces programs with fewer bugs [but I don’t have data to prove it].” TB-L’s proposal was really good at being honest.
Finally, here is an attempt at establishing a rigorous criteria for design assessment in the context of doctoral and post-doctoral research:
- Problem: how important and surprising is the problem and how good is its description? The problem space is, perhaps, the most important component for a piece of design research work. If the design is not well grounded in an interesting and important problem, then perhaps it’s not worth pursuing as research work. If it’s a old hard problem, it should be formulated in a surprising manner. Very often, the novelty of a design lies not in the design itself but in its designer seeing the problem differently. So — surprise me with the problem. Show me insights on the nature of the problem that we don’t already know.
- Potential: what intriguing possibilities are unveiled by the design? Good design research work should open up doors for new avenues of exploration.
- Feasibility: good design research work should be grounded on what is possible to do. The ideas should be demonstrated in the form of a working system.
- Additionally, design research work, like any other research work, needs to be placed in a solid context of what already exists.
This criteria has two consequences that I really like: first, it substantiates our intuitions about proposals such as TB-L’s “linked information system” being a fine piece of [design] research work; second, it substantiates our intuitions on the difference of languages like Haskell vs. languages like PHP. I leave that as an exercise to the reader!
Coming to terms
I would love to bring design back to my daytime activities. I would love to let my students engage in designing new things such as new programming languages and environments — I have lots of ideas for what I would like to do in that area! I believe there is a path to establishing a set of rigorous criteria regarding the assessment of design that is different from scientific/quantitative validation. All this, however, doesn’t depend on me alone. If my students’ papers are going to be shot down in program committees because of the lack of validation, then my wish is a curse for them. If my grant proposals are going to be rejected because they have no validation plan other than “and then we install it in many machines” or “and then we make the software open source and free of charge” then my wish is a curse for me. We need buy-in from a much larger community — in a way, reverse the trend of placing software research under the auspices of science and engineering [alone].
This, however, should only be done after the community understands what science and scientific methods are all about (the engineering ones — everyone knows about them). At this point there is still a severe lack of understanding of science within the CS community. Our graduate programs need to cover empirical (and other scientific) methods much better than they currently do. If we simply continue to ignore the workings of science and the burden of scientific proof, we end up continuing to make careless religious statements about our programming languages and systems that simply will lead nowhere, under the misguided impression that we are scientists because the name says so.
Copyright © Crista Videira Lopes. All rights reserved.
Note: this is a work-in-progress essay. I may update it from time to time. Feedback welcome.