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Standards Compliance - OCC STEP - "AP 242 Edition 2" fully (or more) ?

Data Exchange and Application FrameworkSun, 05/15/2022 - 06:142 replies

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QuestionAuthor

Does the current OCC STEP file generation engine offer, as choices for output format,

a) a file which is fully-compliant with the AP 242 Edition 2 (no more, no less),
b) a file which is fully-compliant with the AP 242 Edition 1 (no more, no less), and
c) a file which is a superset of AP242 Edition 2 ?

Where I am coming from is as a newbie on FreeCAD. I believe they are using OCCT's technology/tools to generate their STEP file. I did confirm that the generated STEP file is reporting itself as formatted to ISO 10303-214.

However, three is no indication if that is compliant with ISO 10303-214:2010 or the earlier ISO 10303-214:2003 (I am guessing the latter because there is no year specification with that format label in the file header.

However, given the evolution of STEP and the fact that the above was "withdrawn" when ISO 10303-242 was first published in 2014, and that even that version of the standard was updated/replaced by ISO 10303-242:2020, there is no guidance provided thru the FreeCAD site as to the "compliance status" at this time, between the STEP AP 214 file being generated and the current AP 242:2020. I am hoping that you can provide those additional details.

I don't have funds to buy those standards, so I have no way to compare them or provide a forward compatibility/breakage chart comparing the element/object types one-by-one.

Going further, I know that this following request may sound extreme but, in my view, it is the only verifiably-provable demonstration of capability.

Would it be possible to provide ... the single-file "all-encompassing" test file ... which fully tests the capacity of the OCC geometry engine and step file generator such that it demonstrates that it can handle all geometry/feature/attribute types in a single source model, and also demonstrates that the STEP engine does indeed handle such a large/complex model and create a well-formed STEP file, which is compliant with AP 242 Edition 2 ?

Thank you,
Author

Discussion

2 archived replies

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01Commenter-1

Compliance to standards is a complex subject. One thing is pretending to be compliant and the other is to actually follow all requirements specified in standard, which cannot be verified without writing some complicating validation tools and collecting exhaustive number of standard test cases.

I don't think that it is feasible / useful putting all possible STEP features into a single test model - even for testing a small single feature several sample models are usually used.

Maybe you may ask NIST STEP File Analyzer authors to clarify some things.

02Author

Thank you for responding, Kirill.

Regarding the comprehensive monolithic design test file ...

As CAD administrator for the division I worked in for a multinational 3 decades ago, working in concert with peers in other divisions, it was the corporation's stance, as for many others back then (in the context of IGES), to have a monolithic design file with all geometry types possible actually used, along with derivative constructions thereof, in the source file. That was then exported to IGES, then imported back into various CAD systems (CATIA, CADAM, Unigraphics, Graftek, Cadra, ACIS, EUCLID, I-DEAS, Pro/ENGINEER) at a time that the corporate CAD platform was under review for replacement.

This "reference model" was also used when subjecting potential suppliers to Vendor Qualification testing, to help triage the set of suitable candidates for contract competitions. For that reason, "lesser" systems were also subjected to the testing/verification, including AutoCAD, Cadkey, MasterCAM, and others I don't remember.

So ... my experience is that such comprehensive monolithic test files are not only practical, but necessary.  Feature-specific testing can only go so far, until many features are thrown into the mix. Such scenarios can sometimes confuse software, primarily in regards to precedence handling and referential integrity of individual components. Such potential problems are not exposed unless the software is subjected to a comprehensive monolithic design test.

Regarding the ISO 10303 AP 242 ...

After further digging, I have identified that version 1 (2014) appears to be the version for which there has been some concerted effort to achieve normative consistency from the various software providers, as noted in reports available http://benchmark.ap242.org/.

Would you be able to point me to the URL where I could possibly see a similar report regarding STEP compliance/portability as applies to the OCCT STEP engine for export/import?

Thank you.