An API design heuristic. For a while now, I've been wondering whether, in the language of Postel's law, one should favour being liberal in what one accepts over being conservative in what one sends. Yes, according to the design principle, a protocol or API should do both, but sometimes, you can't do that. Instead, you'll have to choose. I've recently reached the tentative conclusion that it may be a good idea favouring being conservative in what one sends. Good API design explicitly considers contracts. What are the preconditions for invoking an operation? What are the postconditions? Are the ..read more

A reading of the fourth Don Box tenet, with some commentary. This article is part of a series titled The four tenets of SOA revisited. In each of these articles, I'll pull one of Don Box's four tenets of service-oriented architecture (SOA) out of the original MSDN Magazine article and add some of my own commentary. If you're curious why I do that, I cover that in the introductory article. In this article, I'll go over the fourth tenet, quoting from the MSDN Magazine article unless otherwise indicated. Service compatibility is determined based on policy # The fourth tenet is the forgotten one ..read more

The story of a fiasco. This is the second in a small series of articles titled Trying to fit the hype cycle. In the introduction, I've described the exercise I had in mind: Determining a formula, or at least a piecewise function, for the Gartner hype cycle. This, to be clear, is an entirely frivolous exercise with little practical application. In the previous article, I extracted a set of (x, y) coordinates from a bitmap. In this article, I'll showcase my failed attempt at fitting the data to a polynomial. Failure # I've already revealed that I failed to accomplish what I set out to do. Why s ..read more

A reading of the third Don Box tenet, with some commentary. This article is part of a series titled The four tenets of SOA revisited. In each of these articles, I'll pull one of Don Box's four tenets of service-oriented architecture (SOA) out of the original MSDN Magazine article and add some of my own commentary. If you're curious why I do that, I cover that in the introductory article. In this article, I'll go over the third tenet, quoting from the MSDN Magazine article unless otherwise indicated. Services share schema and contract, not class # Compared to the second tenet, the following de ..read more

An amateur tries his hand at linear modelling. About a year ago, I was contemplating a conference talk I was going to give. Although I later abandoned the idea for other reasons, for a few days I was thinking about using the Gartner hype cycle for an animation. What I had in mind would require me to draw the curve in a way that would enable me to zoom in and out. Vector graphics would be much more useful for that job than a bitmap. Along the way, I considered if there was a function that would enable me to draw it on the fly. A few web searches revealed the Cross Validated question Is there ..read more

A reading of the second Don Box tenet, with some commentary. This article is part of a series titled The four tenets of SOA revisited. In each of these articles, I'll pull one of Don Box's four tenets of service-oriented architecture (SOA) out of the original MSDN Magazine article and add some of my own commentary. If you're curious why I do that, I cover that in the introductory article. In this article, I'll go over the second tenet. The quotes are from the MSDN Magazine article unless otherwise indicated. Services are autonomous # Compared with the first tenet, you'll see that Don Box had ..read more

My inept adventures with a dynamically typed language. This article is the third in a small series about ad-hoc programming in two languages. In the previous article you saw how I originally solved a small data extraction and analysis problem with Haskell, even though it was strongly implied that Python was the language for the job. Months after having solved the problem I'd learned a bit more Python, so I decided to return to it and do it again in Python as an exercise. In this article, I'll briefly describe what I did. Reading CSV data # When writing Python, I feel the way I suppose a scrip ..read more

A reading of the first Don Box tenet, with some commentary. This article is part of a series titled The four tenets of SOA revisited. In each of these articles, I'll pull one of Don Box's four tenets of service-oriented architecture (SOA) out of the original MSDN Magazine article and add some of my own commentary. If you're curious why I do that, I cover that in the introductory article. In this article, I'll go over the first tenet, quoting from the MSDN Magazine article unless otherwise indicated. Boundaries are explicit # This tenet was the one I struggled with the most. It took me a long ..read more

Twenty years after. In the January 2004 issue of MSDN Magazine you can find an article by Don Box titled A Guide to Developing and Running Connected Systems with Indigo. Buried within the (now dated) discussion of the technology code-named Indigo (later Windows Communication Foundation) you can find a general discussion of four tenets of service-oriented architecture (SOA). I remember that they resonated strongly with me back then, or that they at least prompted me to think explicitly about how to design software services. Some of these ideas have stayed with me ever since, while another has ..read more

Statically typed languages are also good for ad-hoc scripting. This article is part of a short series of articles that compares ad-hoc scripting in Haskell with solving the same problem in Python. The introductory article describes the problem to be solved, so here I'll jump straight into the Haskell code. In the next article I'll give a similar walkthrough of my Python script. Getting started # When working with Haskell for more than a few true one-off expressions that I can type into GHCi (the Haskell REPL), I usually create a module file. Since I'd been asked to crunch some data, and I was ..read more