I just wanted to add an observation that is related to
the questions about ambiguities in natural language and
the critical need for precision in certain applications. (01)
There was a recent story about problems in the development
of the Airbus 380. One of the critical issues was that
the 300 miles of wiring that was being assembled in France
didn't fit through the holes in the fuselage that was being
built in Germany. (02)
The Airbus and Boeing designers were using the same CAD
(Computer Aided Design) system called Catia. But Boeing
forced all their developers and suppliers to upgrade all
their software in lock-step every 3 months. (03)
For Airbus, however, the French were using Catia Version 5,
but the Germans were using Catia Version 4. The result was
that the holes designed by the Germans didn't fit the wiring
designed by the French. (See below.) (04)
In English (and every other NL), there is a word for "hole",
but the exact details of how a hole is specified are seldom
stated precisely. But for designing an airplane the amount
of detail can be staggering. Discrepancies between the way
a hole is specified in the two systems created an ambiguity
that was not detected during the design stage. (05)
They used to say that the complete specifications (on paper)
for the Boeing 747 wouldn't fit in a 747, and if it could,
it would make the plane too heavy to take off. But the amount
of detail for the new planes is so much more voluminous that
nobody ever puts it all on paper. For Boeing's forthcoming
787 (the Dreamliner), the amount of data for the design takes
about 16 terabytes of storage. (06)
That's a lot of potential for unnoticed ambiguities to create
disastrous problems -- which can, as in this case, cost
billions of dollars in redesign and lost sales. Even worse,
some problems could go undetected until the plane is built and
put into service. Then it becomes a matter of life or death. (07)
John
_____________________________________________________________ (08)
Both [versions of Catia] are able to represent objects in 3D, but that's
where the similarities end. Engineers using Catia V4 must use a manual
process to create the geometry of a model. To create a hole inside an
object, for example, the system requires them to subtract a cylinder
from the space to define where the hole should exist. By contrast, the
product designer using Catia V5 simply feeds in a set of engineering
instructions -- in effect, describing the location and dimensions of the
hole -- and the geometry is automatically created. "V5 is higher-level,
more intuitive," says Doug Cheney, product manager for CAD
interoperability quality at ITI TranscenData, a developer of CAD
translation software. "With the older system, the engineer figures out
the geometry; with the new one, the system finds the best geometric
solution." (09)
Airbus engineers ran afoul of this basic difference when creating the
miles of wiring to be inserted inside the A380 fuselage. The engineers'
"notes" -- appendices that describe details of models such as curves --
sometimes are not replicated in the translation between Catia V4 and V5,
says David Prawel, president of Longview Advisors, a Loveland,
Colo.-based consulting firm specializing in 3D software issues for
manufacturing. In other words, key notes required to duplicate a 3D
model showing electrical wires as they twist and bend through the
aircraft may fail to reappear in full and accurate detail when a design
file in one system is converted to a file in the other. (010)
Source: (011)
http://www.baselinemag.com/print_article2/0,1217,a=200193,00.asp
PLM: Boeing's Dream, Airbus' Nightmare (012)
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