[wg11] Minutes of Part 21 e3 DIS testing telecon on May 21, 2014

Wed May 21 13:52:56 EDT 2014

All,

If you would like to take part in the technical discussions please join 
the WG11 e-mail exploder by filling in the appropriate fields at the 
following address

http://lists.steptools.com/mailman/listinfo/wg11

Martin Hardwick
STEP Tools, Inc.

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

*P21 e3 DIS Testing*

Minutes of May 20, 2104 Telecon

    Attendees

Martin Hardwick <hardwick at steptools.com> <mailto:hardwick at steptools.com>
Robert Lipman <robert.lipman at nist.gov> <mailto:robert.lipman at nist.gov>
Jacques Heinisch <jacques.heinisch at 3ds.com> 
<mailto:jacques.heinisch at 3ds.com>
Jochen Fritz <jfritz at steptools.com> <mailto:jfritz at steptools.com>
Michael Benda <mjbenda at rockwellcollins.com> 
<mailto:mjbenda at rockwellcollins.com>
Hedlind Mikael <mikael.hedlind at scania.com> 
<mailto:mikael.hedlind at scania.com>
Nicolas Figay <nicolas.figay at eads.net> <mailto:nicolas.figay at eads.net>
Dave Loffredo <loffredo at steptools.com> <mailto:loffredo at steptools.com>
Ed Paff <ejp at transcendata.com> <mailto:ejp at transcendata.com>
Tom Thurman <thomas.r.thurman at imonmail.com> 
<mailto:thomas.r.thurman at imonmail.com>

    PMI Splitting

ITI has split the sp3_boxy file produced by NIST into a geometry file 
and a pmi file. STEP Tools has viewed the geometry file and is working 
on a viewer for the separated pmi file. The two files and the original 
NIST data can be found at the following URL:

ftp://www.steptools.com/private/P21e3_DIS_testing/PMI/

·We decided the names of the anchors should be made more meaningful by 
including the type name of the destination entity in each anchor name.

·We are developing open-source software to merge and split the files. 
The software is to be called the */Thunder Code/* because two files 
enter and one file leaves.

·The Thunder Code will use mappings to determine where to split files.

    ZIP Assemblies

STEP Tools has developed a ZIP file P21 e3 equivalent for the as1_ac.stp 
data set. The example is an outline. Except for the step files in the 
component sub-directory none of the data files are correct. The ZIP and 
the original data can be found at the following URL:

ftp://www.steptools.com/private/P21e3_DIS_testing/ZIP_Assembly/

·We decided the sub-tree directory names should include the NUAO 
identifier(s) for their corresponding node in the assembly tree.

·We learned that the LZMA algorithm has been shown to make STEP files 
three times more compressed than the more commonly used deflate 
algorithm, but at the cost of an increase in the compression time.

·We learned that each compressed file is required to document the 
algorithm used for its compression in its header and that different 
components in the same ZIP can used different compression algorithms.

·We recommended that the choice of the best compression algorithm should 
be left to the end user and that the standard should be silent on the 
matter.

**

    Unit Definitions

Tom Thurman has developed a set of files to show how the unit 
definitions of a STEP model can be centralized to one location. A set of 
sample files showing how the new units might be defined can be found at 
the following URL:

ftp://www.steptools.com/private/P21e3_DIS_testing/Units/

·If implementors are required to pick the right file then some will pick 
the wrong file name by mistake so we recommend that all of the unit 
definitions be put into one file.

·We should consider using URN's for the unit definitions. A Universal 
Resource Name (URN) is a standard definition for a concept that reading 
algorithms are required to understand.

·The following URL and URN definitions are roughly equivalentexcept the 
URL identifies a "real" file, and the URN requires the reading software 
to implicitly know the referenced definitions

<http://standards.iso.org/iso/10303/tech/reference_data/41/si_base_units.stp#METRE>;

<urn:iso:std:iso:10303:-41-:tech:unit:metre>;

Explanation of URN:

urnIndicates this URI is a URN, instead of the more common URL (http)

iso URN namespace  (other examples are oid, usbn)

stdISO standard

isooriginating organization (other examples are iec, iso-ies, iso-cie)

10303STEP standard

-41-part of multipart standard (hyphens required)

Techassociated or embedded resource defined by committee that created 
the standard

<the rest>unspecified -- controlled by committee.

The iso namespace is defined by RFC 5141 
(http://tools.ietf.org/html/rfc5141)

·The unit definition files need not be signed because their 
trustworthiness will be implied by their being posted on the ISO web 
site. However, they may be signed so that reading software can determine 
if they have changed since they were last read.

    Digital Signatures

We plan to add a section to the files for digital signatures. The new 
capability will be modeled after the tools used to sign the authenticity 
of DLL's. The new capability will allow the file reader to verify its 
source, and validate that it has not been tampered with since it was 
written by the source.

·The digital signature section will be the last one in the file

·The signature will include a hash of all the contents of the file 
before the signature section.

·There may be multiple signatures when multiple organizations are 
required to authorize the file

·Any organization with the public key for the signature will be able to 
read and verify the hash value.

·Only the organization with the private key will be able to write the 
signature.

·The signature content will be as defined in the Cryptographic Message 
Syntax (CMS) defined by RFC 5652, clause 5 
(http://tools.ietf.org/html/rfc5652).

·The CMS structure will be encoded as Base-64 within the P21 signature 
section.

·We will create open source examples to read and write the signatures.

·We will create a server to create signatures and certificates for 
testing purposes.

    Other

·We will continue to use the Wg11 exploder for broadcasting. Other 
exploders may be used occasionally for sending finished items such as 
these minutes, but anyone who wants to participate in the technical 
discussions must join this exploder which can be found at the following URL

http://lists.steptools.com/mailman/listinfo/wg11

·Please invite anyone who is interested in Part 21 to join the exploder.

·Tom Thurman will post these minutes to the appropriate place on the ISO 
web site.

·The next conference call will be held on Thursday June 5 at 4PM Paris, 
3PM London, 10AM New York and 7AM Seattle.

    Action Items

1.Make a New ZIP assembly example with the NUAO names.**

2.Consolidated all the unit definitions into one file.**

3.Create an open source repository for the codes to split and merge 
files (thunder codes), and the codes to read and write digital signatures.**

4.Investigate how the recommended practices of the EADS TDP project can 
be applied to the digital signatures section.

As recorded by Martin Hardwick <hardwick at steptools.com> 
<mailto:hardwick at steptools.com>

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