Two Herons, a Chiffchaff and a Greater Spotted Woodpecker

Today was my first day back at work after a week off. Coming out of Farnborough North station this morning a pair of herons flew overhead.  One gave a kraak call (like the heron at the beginning of Tarka the Otter) and they flopped off at tree-top height, along the railway towards Wokingham.   Over the bridge, a chiffchaff was singing high up, first from a tree top, then from some power lines (the ones fitted with little 'springs' to make them more visible to low-flying swans).  A minute later, in the woods, a greater spotted woodpecker landed in a tree just above me, showing the red patch under its tail. 

You don't get that from a car!

The +CAL Algorithm Language

Leslie Lamport has extended his TLA+ Tools with +CAL, a language to specify algorithms in.  As he explains:

+CAL (pronounced "plus-CAL") is an algorithm language based on TLA+.  A +CAL algorithm is translated to a TLA+ specification, which can be checked with the TLC model checker.

An algorithm language is for writing algorithms, just as a programming language is for writing programs.  The introduction to the +CAL manual (see below) explains how algorithms differ from programs, and how +CAL differs from programming languages. 

+CAL comes with two syntaxes, one Pascal-like and the other Java-like.  This looks like a cynical attempt to attract the curly-brace rabble (but I reckon most of them would probably fail to appreciate Lamport's distinction  between an algorithm and a program).

First Gosling of the Year

I went round the university lakes with Zoe and Liz this afternoon, the first time for several weeks.  There weren't many birds around; maybe they are busy nesting.  Any how, the pair of Egyptian geese had one tiny gosling.  It must have been only a few days old.

Update on Sat 2006-04-15 by Tristram Brelstaff

We were later told that the gosling hatched out on the Friday so it will have been no more than 2 days old when the picture was taken.

Michael Jackson's Papers

I have a lot of time for the software development guru Michael Jackson: he has thought deeply about important problems, and has come up with original, interesting and practical ways of solving them.  Recently, he has revamped his publications page to include on-line copies of many more of his papers.  This now provides lots of good reading on the subjects of Problem Frames, Requirements and Specification, as well as his earlier work which lead to JSP and JSD.

(If there was a competition for the coolest title for a computing science paper then Zave and Jackson's Four Dark Corners of Requirements Engineering would be my nomination.)

Nuthatch

I am spending a few days with Zoe at my father's in Guisborough.  It has been mostly cold and wet, yesterday it snowed.  This morning was clear and sunny so we went for a walk up Roseberry Topping.  On the way back we saw a nuthatch (Sitta europaea).  It was in a birch tree near the Hutton Village end of the forestry track that runs along the eastern side of Bousdale.