Category Mistakes

Category mistakes by Dijkstra, Hoare, and others

Ensmenger & Flowcharts

Dated: 

8 July 2017

One of the questions that keeps me awake (during the day) is the following one:

What did a “computer program” mean to Actor X in 1973?

For example, both Christopher Strachey and Edsger Dijkstra viewed a “computer program” as a mathematical object, albeit of a very different kind [1]. (A decade or more earlier, both men did not associate computer programs with mathematical objects pur sang). But what about large parts of the North American computer industry in 1973? How did actors in this field view a “computer program” in 1973?

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Michelle Obama vs. the Gatekeeper

Dated: 

15 October 2016

Category mistakes and incomputability claims seem to go hand in hand. I have given one modern example in connection with programming languages and Michael Hicks and another one directly concerning the diagonal argument. In the present blog post I shall give one more example, based on an excerpt from my rejected POPL paper entitled: `Category Mistakes in Computer Science at Large.' Specifically, I shall zoom in on the “code improvement problem,” as discussed by Albert R. Meyer and Dennis M.

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The POPL Gatekeeper

Dated: 

6 October 2016

There is an obvious distinction to be made between computers (which include laptops and iPads) on the one hand and mathematical models on the other hand. Strictly speaking, it is wrong to say that “a computer is a finite state machine.” That's like speaking about a mathematical model as if it coincides with reality. Unfortunately, it is unusual to make these kinds of observations explicit in computer science, as I am doing now and as I have done in my paper entitled `Category Mistakes in Computer Science at Large.'

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Parnas and Chaudhuri

Dated: 

4 October 2016

The topic of `Category Mistakes,' which I have discussed in my four previous blog posts is not limited to digital systems. Engineers in all areas use models and they, too, can potentially fall into the trap of mistaking the model for reality.

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Analysis Tools and Michael Hicks

Dated: 

21 September 2016

Before really discussing category mistakes in computer science in follow-up posts, I will first continue testing my aforementioned categories on the writings of people I admire the most. I shall take a 2014 blog post, written by Michael Hicks in connection with the Heartbleed bug. (His post was written on July 1st, 2014 and I accessed it on September 19th, 2016.)

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Technical Artefacts and John Reynolds

Dated: 

19 September 2016

Before discussing several "category mistakes" in computer science in follow-up posts, it is much preferred to first introduce a few categorical distinctions and definitions and to subsequently test these concepts on the writings of computer science's greatests (i.e., the writings of the people I and many others admire the most).

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Category Mistakes in Computer Science

Dated: 

15 September 2016

In 2006 I defended my Ph.D. thesis at KU Leuven. Dr. X from abroad was in my defense committee. He had taken the liberty a few days earlier to share with me some of the "fundamental limitations" he had found with regard to transformational systems, such as the system I had designed, implemented, and documented for my Ph.D. defense. (A comprehensive overview of my system later appeared in Science of Computer Programming [1]). Dr. X had already published his theoretical insights and he wanted me to incorporate his findings into my Ph.D. dissertation.

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