[step-manufacturing] STEP-NC and XML as standard

[Carlsson Per-Arne]

 Hi,
Vince have a point in his last chapter (see below); we as end-user now also need to consume the information that a STEP-NC file contain.
Earlier (in the beginning) we was happy if we could transfer information to a NC-controller and make it produce chips. We have also shoved that many different processes can use STEP-NC as information carrier.

If the express schema or file-structure is preventing us to easy access and use information for our processes defined by STEP-NC files, we do NOT get the total potential out of what STEP-NC is capable of support us with.

It is time to invent how we can consume information from STEP-NC to our manufacturing environment, people and systems, to be more productive/effective. Now we have an umbrella of software from many vendors to mange this information and the trend is increasing with more systems.

If it possible I can participate by phone or "net meeting" on Thursday before lunch (your time) if there are time for discussion or questions.



Best regards / Med vänlig hälsning,
P-A Carlsson
_________________________________________________
Per-Arne Carlsson
Volvo Information Technology AB
Dept 9511, Geo. loc. VAKV-D1
SE-405 08 Gothenburg, Sweden

Telephone: +46 31 32 22 696
Mobile Phone +46 73 90 22 696
E-mail: per-arne.carlsson at volvo.com


-----Original Message-----
From: step-manufacturing-bounces at steptools.com [mailto:step-manufacturing-bounces at steptools.com] On Behalf Of Vincent Marchetti
Sent: den 14 juni 2010 05:15
To: step-manufacturing at steptools.com
Subject: Re: [step-manufacturing] STEP-NC and XML as standard

I am Vince Marchetti and am responsible for the website (http://spri.kshell.com
) that Per-Arne Carlsson mentioned in his June 10 note to the group. I
would like to add to some of the points he made.

Per-Arne discussed the possibility of using XSLT to read the XML (Part
28) encoding of STEP files. I recall having seen a published paper on
this approach but I cannot recall or find by searching the actual
reference. I'm sure it's true in a theoretical way that you can do
anything with XSLT operating on the XML encoding that you can in any
other programming language or discipline, but this approach becomes
difficult because of the mismatch between the information models that
XML/XSLT are intended for and the structure of a STEP file based on an
EXPRESS schema. XML/XSLT works well with information that is
fundamentally hierarchical; with things (parent-nodes) containing
other things (children-nodes) that in turn contain other things
(grandchildren, etc). More general relations can be implemented with
the special xml:id attribute; but built-in support is shallow (for
example, it's tricky to have a collection of references to other
things). On the other hand, the information is a STEP file tends to be
a wide-open network of things (entities); there are in fact a large
number of entities whose only information content is links
(references) to other entities. In short, I am skeptical about the
practicality of using XSLT to directly work with Part 28 encodings of
files except for very basic processing (for example, finding the
values of the "name" attribute of product entities referenced in a
STEP file)

Per-Arne mentioned the spri website, so perhaps I can detail it's
relation to the points he made. That website demonstrates the
feasibility of processing a STEP file by deriving a set of "views"
from a single STEP file. In the terms of the STEP-NC files this group
is interested in, one view might present a hierarchy of workplan -->
working_steps --> toolpath; another view may present working steps
organized by geometric and manufacturing features of the workpiece,
another view may be organized my cutting tool requirements. Each view
is a simplified structure, with redundant content, based on the
original STEP-NC file. The views are designed to be readily encoded as
XML files and readily accessible with XSLT scripts. From these XML
views it is then possible to generate specific content such as HTML
rendering for viewing on a browser, or for entry into a database or
other end application, moreover with XSLT you can combine, or as they
say on the web "mash-up", the information from several views. There is
some progress in extracting enough geometry from the STEP file to
deliver 3D visual representations of the products in the file as X3D
(see www.web3d.com) files, again in XML encoding.  The generation of
these views from the original STEP file is achieved by translating
(through a basic crank and grind C++ application) the STEP file into
a collection of Prolog (the computer language Prolog) assertions; then
by analysis of those assertions with the techniques of logic
programming afforded by Prolog (see http://www.kshell.com/prolog/pages/why_prolog/
  )

I see these techniques; which consume rather than produce STEP
content; as complementary to the valuable work of this group in
showing how to generate STEP-NC files useful for cutting actual metal.

Vince Marchetti

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