[aadl]: FW: Traceability of requirements
Peter Feiler
phf at sei.cmu.edu
Mon May 18 11:16:28 EDT 2009
Dear all,
You might enjoy the message below.
In the case of AADL we also have an interesting requirements trace.
Why is the syntax of AADL the way it is?
AADL was derived from MetaH to benefit the semantic framework from MetaH.
To get the standard out quickly we did not want to reinvent the syntax.
MetaH has a syntax that looks like Ada. When Steve Vestal designed MetaH he was familiar with Ada and implemented the toolset in Ada.
Where does Ada have its syntax from? It came from the green team.
Who was the lead of the green team?
The rest is for historians of programming languages.
Peter
-----Original Message-----
From: Jorgen Hansson
Sent: Monday, May 18, 2009 4:28 PM
To: Dionisio de Niz; Lutz Wrage; John Hudak; Peter Feiler
Subject: Traceability of requirements
...enjoy... Jorgen
The US standard railroad gauge (distance between the rails) is 4 feet, 8.5 inches. That's an exceedingly odd number.
Why was that gauge used? Because that's the way they built them in England, and English expatriates built the US railroads.
Why did the English build them like that? Because the first rail lines were built by the same people who built the pre-railroad tramways, and that's the gauge they used.
Why did 'they' use that gauge then? Because the people who built the tramways used the same jigs and tools that they use d for building wagons, which used that wheel spacing.
Why did the wagons have that particular odd wheel spacing? Well, if they tried to use any other spacing, the wagon wheels would break on some of the old, long distance roads in England, because that's the spacing of the wheel ruts.
So who built those old rutted roads? Imperial Romebuilt the first long distance roads in Europe (and England ) for their legions. The roads have been used ever since.
And the ruts in the roads? Roman war chariots formed the initial ruts, which everyone else had to match for fear of destroying their wagon wheels. Since the chariots were made for Imperial Rome, they were all alike in the matter of wheel spacing. Therefore the United States standard railroad gauge of 4 feet, 8.5 inches is derived from the original specifications for an Imperial Roman war chariot.. Bureaucracies live forever.
So the next time you are handed a specification/procedure/process and wonder 'What horse's ass came up with it?', you may be exactly right. Imperial Roman army chariots were made just wide enough to accommodate the rear ends of two war horses. (Two horse's asses.) Now, the twist to the story:
When you see a Space Shuttle sitting on its launch pad, there are two big booster rockets attached to the sides of the main fuel tank. These are solid rocket boosters, or SRB's. The SRB's are made by Thiokol at their factory in Utah . The engineers who designed the SRB's would have preferred to make them a bit fatter, but the SRB's had to be shipped by train from the factory to the launch site. The railroad line from the factory happens to run through a tunnel in the mountains, and the SRB's had to fit through that tunnel. The tunnel is slightly wider than the railroad track, and the railroad track, as you now know, is about as wide as two horses' behinds.
So, a major Space Shuttle design feature of what is arguably the world's most advanced transportation system was determined over two thousand years ago by the width of a horse's ass. And you thought being a horse's ass wasn't important? Ancient horse's asses control almost everything... And CURRENT Horses Asses are controlling everything else.
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