Specifications are for Reasoning From

We write specifications of systems in order to be able to reason about those systems.  This reasoning can be formal or informal. It can take the form of proving properties, deriving properties or refining the specification to code.  The purpose of specifications is to allow this reasoning to take place, ie: specifications are for reasoning from.  Looking at specification this way leads me to make the following suggestions:

• Specifications should be written in a way that makes reasoning easy.  A way to do this is to write them as conjunctions of ready-to-use proof steps, with the pre-conditions and variables of each step clearly visible.
• Conciseness is not necessarily important in specifications.  Not including irrelevant material is important, as is clearly laying out the relevant material, but using abstruse theories to make the specification as short as possible is not.
  
• Graphical notations that have not been designed with reasoning in mind should be avoided.  Just because a notation is graphical does not mean that it makes reasoning easy.
  

Stargazing by Peter Hill

I only picked up this book because of its title.  I only bought it because, when I opened it, I came across a mention of the island of Pladda.

Back in in the summer of 1972, when I was 13, our family spent three weeks staying with friends on the Isle of Arran.  That holiday was to me rather like what the trip to Corfu was for the young Gerald Durrell in My Family and Other Animals, except that it wasn't wildlife that interested me then, but stars.  Because of the lack of street lamps the skies were darker than any I had seen before and, because of the sea horizon, I could actually see stars further south than I could from back in Cleveland.  And the views of the Milky Way through binoculars were simply breathtaking.  On my return from that holiday I joined the British Astronomical Association and took up variable star observing in earnest. 

Although we were based at Pirnmill, in the north-west corner, we explored all parts of the island, and often from the mountains or from the southern shore-line the islands of Pladda and Ailsa Craig were visible in the distance.  Pladda was small, flat and close in, Ailsa Craig, large, hemispherical, and much further out, down the Firth of Clyde.

In the following summer, that of 1973, Peter Hill, an art student from Dundee, took a holiday job as a lighthouse keeper and spent a few weeks on Pladda and then a few more on Ailsa Craig.  Stargazing is his account of that time, of the characters he worked with, the way of life, and the things that happened to him.  It is an enjoyable, heart-warming read. I am sure that would have lead to hordes of people applying to work as lighthouse keepers, if only the lighthouses hadn't all been automated by now.

Life of Pi by Yann Martel

A very strange book.  The Financial Times reviewer got it spot on when said it is like "Joseph Conrad and Salman Rushdie hallucinating together...".  However, I nearly gave up three quarters of the way through, leaving Pi stuck in the middle of the Pacific Ocean, but I eventually came back to it and followed him through to landfall and beyond.  And I am glad now that I did, even though I did find the ending a little disappointing.  Anyhow, if ever I have to live in close quarters with a Bengal tiger, I now know what I have to do.

31 Songs by Nick Hornby

In February 2003 I broke my ankle while taking a short cut across the Inner Distribution Road in Reading and was off work for two months.  After the first week of agony, the pain subsided and my life then became a battle against boredom and the wasting away of my leg muscles.  To combat the the latter I would lie on my back and waggle my legs in the air as if I was walking; to combat boredom I would listen to the radio.  

One of the highlights of that time was a Radio 4 serialization of readings by Nick Hornby from his book 31 Songs.  This was broadcast in the mornings, just after my wife and daughter had left the flat.  I would get dressed, stagger through to the kitchen to make myself a cup of coffee (a non-trivial operation on crutches), lean my crutches against the wall and sit down at the table with my ankle propped up on a stool.  And then, because it had taken so much effort, I would sit there for the next hour or so listening to the radio.  And during one week, each morning this down-beat sounding middle-aged man would come on and talk for 15 minutes about some pop song that he liked.  Most of the songs he talked about I had not heard of but, in spite of that, I began to look forward to hearing him.  There is a fascination in listening to someone enthuse knowledgeably about something, no matter how trivial that something might be.

Well, in time my ankle mended, I learned to walk again, went back to work and my life returned to normal.  Then, a few months ago, I was wandering through Waterstone's one Saturday morning when the cover of 31 Songs caught my eye.  I bought a copy there and then, and read it over the next few days.  And yes, it was enjoyable, but not as enjoyable as listening to the radio programs when I was stuck in our flat with nothing else to do.  And no, I have not bought any CD's as a result of reading this book, but  I did use Google to find a free downloadable copy of Royksopp's Night Out.

Remains of the Day by Kazuo Ishiguro

A beautiful, sad book.  I originally bought it because I liked the cover - a painting by Maeda Toshiro.  I am glad I didn't seen the film before I read the book though - I am sure it would have spoilt it for me.