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<div class="moz-cite-prefix">On 6/11/2014 12:39 PM, Barkmeyer,
Edward J wrote:<br>
</div>
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<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Martin,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Why
is:
</span><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a
moz-do-not-send="true"
href="http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH"><http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH></a></span>;<o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif"">less
“convoluted” than:</span>
<span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
urn:iso:std:iso:31:term:metre</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">???</span></p>
</div>
</blockquote>
You tell me. I want to use <urn:step:inch><br>
<br>
As implementors we have found that less typing means less scope for
mistakes. <br>
<br>
If there is going to have to be lots of typing then <span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"></span><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif""><a
moz-do-not-send="true"
href="http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH"><http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH></a></span>;
is better than <span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
urn:iso:std:iso:31:term:metre </span>because there are lots of
ways to check for badly type URL's and hardly any to check a badly
typed URN.<br>
<br>
Your URN requires me to remember:<br>
1. Type iso twice<br>
2. The standard number is 31<br>
3. The concept being defined is a term<br>
<br>
As an implementor I can do all this. Just look at what we did for
units in Part 21 Edition 1 and 2. <br>
<br>
Martin<br>
<br>
<br>
<span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
http: form just uses a different ISO CS directive for formulating
IRIs, which is “jealously guarded” by ISO CS in exactly the same
way!<o:p></o:p></span>
<blockquote
cite="mid:c0ceeacecffb49bcbb2b36fe87779f71@BN1PR09MB107.namprd09.prod.outlook.com"
type="cite">
<div class="WordSection1">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">In
both cases, ISOCS specifies what everything up to the “tech”
part must be, and the SC gets to define what follows.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
point of the ISO URNs of the form above is that MERELY by
having the term defined in an existing ISO standard, there
IS a standard IRI for the term. And if multiple standards
define “metre”, then it is very important that you know
WHICH meaning is intended by the reference!
<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Why
would it be better for ISO 10303 to define what it means by
“inch” than what some industry reference standard defines
“inch” to mean? Do I have to find a different IRI if I am
using an ASTM standard? or an API standard? <o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
problem is to get a reference standard that defines the
“conversion based units” (English measure, et al.) that we
want to be able to use, and then to use one of the
ISO-specified forms for creating the corresponding IRI,
whether it begins http: or urn:. Enabling such things is
exactly why ISOCS went to the trouble of registering the URN
and URL forms and publishing the corresponding directives.
And if the reference standard is not an ISO standard, then
we will be bound by whatever URI syntax that particular SDO
set up. So, if urn:ifc, or <a class="moz-txt-link-freetext" href="http://ifc.org/">http://ifc.org/</a>, is an ICANN
registered prefix, and the IFC defines urn:ifc:inch, or
whatever “convoluted” form IFC decides on, we could use that
and be done.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">The
point of all this is that the references for constructing
IRIs are already in place. What is necessary is the *<b>standard</b>*
that defines the terms you want to use, so that the IRI that
refers to that term in that standard can be employed. Stop
worrying about the IRIs and figure out where/what the
reference standard is to be. By way of assisting in this,
I have put in a request to a NIST SI/BIPM person to
identify an appropriate specification for English measures,
but I have not yet received a response.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Ed<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<div style="border:none;border-left:solid blue 1.5pt;padding:0in
0in 0in 4.0pt">
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"
style="text-autospace:ideograph-numeric ideograph-other"><b><span
style="font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-family:"Tahoma","sans-serif";color:windowtext">
Martin Hardwick [<a class="moz-txt-link-freetext" href="mailto:hardwick@steptools.com">mailto:hardwick@steptools.com</a>]
<br>
<b>Sent:</b> Wednesday, June 11, 2014 6:35 AM<br>
<b>To:</b> Thomas.r.thurman<br>
<b>Cc:</b> Barkmeyer, Edward J; Thomas Liebich; wg11;
Palmer, Mark E. Mr.; <a class="moz-txt-link-abbreviated" href="mailto:magne.valen.sendstad@gmail.com">magne.valen.sendstad@gmail.com</a><br>
<b>Subject:</b> Re: [wg11] units of measure, from
Minutes of Part 21 E3 DIS testing telecon on June 5,
2914<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<div>
<p class="MsoNormal"><br>
Again my purpose is to investigate how P21 e3 might help.
The most we can venture is to produce some recommendations
and examples.<br>
<br>
My summary of the previous e-mails is that the ISO
namespace <urn:iso> is jealously guarded to keep the
peace between the committees. We are never going to be
able to use it to make something easy for the
implementors.<br>
<br>
However, before giving up on URN's I would like to get
opinion on the following: Can we define our own
namespaces?<br>
<br>
We might do this for each standard, or at the level of
SC4.<br>
<br>
For example, if we decide to use URNs to define units for
STEP then<br>
1. The URN for inch might be <urn:step:inch>;<br>
2. The URN would be mapped by appropriate wording in the
appropriate place to the URL
<br>
<a moz-do-not-send="true"
href="http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH"><http://standards.iso.org/iso/10303/tech/reference_data/-41/units.stp#INCH></a>;<br>
3. The URN would only have to have meaning for a STEP
model.<br>
<br>
We would then do the same for ifc <urn:ifc:inch> and
iso15926 <urn:iso15926:inch> etc.
<br>
<br>
The appropriate wording in #2 could be words in the
standards document, or it could be a rule in the standards
document telling you where to find a server with the
permitted URNs.
<br>
<br>
Martin Hardwick<br>
Team Leader ISO STEP-Manufacturing<br>
<br>
<br>
<br>
On 6/10/2014 8:15 PM, Thomas.r.thurman wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<p class="MsoNormal">The purpose behind the units thing in
P21 ed3 EXAMPLEs is to help move things forward,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">as opposed to just having examples in
p41.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">The BIPM has made general quantities
and units document publicly available, but ISO 80000-x <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">is still behind a paywall which means
I have to buy a copy of it to understand what a term
means.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
<div>
<p class="MsoNormal">What is the <b><i><u>business</u></i></b>
process for moving forward?<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Regards,<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">Tom<br>
Sent from my iPad<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal" style="margin-bottom:12.0pt"><br>
On Jun 10, 2014, at 4:11 PM, Martin Hardwick <<a
moz-do-not-send="true"
href="mailto:hardwick@steptools.com">hardwick@steptools.com</a>>
wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<div>
<div>
<p class="MsoNormal"><br>
Hi Ed,<br>
<br>
Thanks for these comments and before anyone gets the
wrong idea let me state emphatically that Part
Edition 3 is NOT, NOT, NOT planning to define any
units. We are only looking at what might become
possible if URI's are allowed in the Part 21
standard.<br>
<br>
One option for the relevant committees is to keep
the status quo and demand that all units are defined
from first principles as is currently the case in
all the STEP Application Protocols. Thus every time
an inch is used it must be defined as being 25.4
millimeters. (As an aside I wonder what would
happen if a file defined an inch as 25.3
millimeters. Would the software notice? Would it
follow through and convert all the units by the
given formula. Would the result be a correct model?
What about the accuracy constraints? Has STEP been
consistent about applying the conversion across all
the cases?)<br>
<br>
The second option is to use URL's. This is the
option that is being most actively investigated by
the P21 e3 group. This option is currently running
into several small issues with respect to conversion
based units. As I understand it the issues are
derived from problems in the PLIB expression schema,
but on a more personal level I have always thought
it crazy to encode expressions in the PLIB
expression schema.<br>
<br>
This started me thinking about the URN option in
more detail. As I understand it a URN is used when
the systems are expected to "know" the definition.<br>
<br>
Hence I wonder why we cannot define<br>
<br>
<urn:iso:inch><br>
<br>
In the context of an AP242 file this would mean the
current definition only with the conversion
GUARANTEED to be 25.4. For an OWL system it would be
whatever OWL systems expect and so on. It is a URN
so nothing has to be at the other end of the
definition, but something could be so STEP could say
this URN is defined by the definitions at the
following URL (which can then be as complex as any
standards organization can imagine).<br>
<br>
I really wonder what the advantage of a convoluted
URN such as <span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">urn:iso:std:iso:31:term:metre</span>
might be. Does this mean that different standards
groups are going to define different metres?<br>
<br>
There is also the practical issue for system
implementors of what to do if someone types the
URN's slightly wrong which increases as the URN gets
longer.
<br>
<br>
As an implementor <urn:iso:inch> seems just
about acceptable because there is very small
possibility that we will want to have two
definitions for inch in STEP files - one defined by
ISO and another defined by Martians
<urn:mars:inch>. A more practical example
might be the definition of pint which is different
between the UK <urn:iso:uk:pint> and the USA
<urn:iso:usa:pint>. I can see that ISO might
shy away from making this kind of distinction, but
in this case can STEP should define its own name
space <urn:step:inch> for its own STEP files.<br>
<br>
Thanks for your attention. If we are going to have
to write URN's that are as long and convoluted as
the URL's then we may as well stick with the URL's,
so I am hoping there is a better solution.<br>
<br>
Martin<br>
<br>
<br>
<br>
On 6/10/2014 4:42 PM, Barkmeyer, Edward J wrote:<o:p></o:p></p>
</div>
<blockquote style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Martin,</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">I
agree that fuddling with Part 41 representations
of measurement units that should have reference
IRIs is “so 1990s”. But moving on requires a
wider commitment.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">urn:iso:
... is a well-defined identifier form, and ISO CS
is the registry for it. See IETF RFC 5141. (<a
moz-do-not-send="true"
href="http://www.rfc-editor.org/info/rfc5141">http://www.rfc-editor.org/info/rfc5141</a>)</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Some
of these units are defined terms in ISO 31, ISO
1000 and ISO 80000. As a consequence they have a
well-defined URN per the RFC.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">For
example, the URN for ‘metre’ is (I think):</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
urn:iso:std:iso:31:term:metre</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">It
is doubtless the case that one of the ISO
measurement units standards defines cm/s, but it
is unlikely that any defines ‘furlong’ or ‘inches
per second’. That is why Part 41 has the
conversion_based_unit construct.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">SC4
has authority from ISOCS to define ISO URNs by
attaching :tech:<whatever> to any (Part of
any) SC4 developed standard identifier, with the
proviso that these identifiers are, in fact,
defined in the technical specification. It is in
fact possible for Part 21 to specify URNs of the
form:</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
urn:iso:std:iso:10303:tech: xxx</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">without
identifying the Part number. I suspect that WG12
would consider it inappropriate for Part 21 to
contain such specifications, however.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Further,
there is an issue in WG3 to align ISO 15926-4 with
ISO 80000 and perhaps to incorporate some elements
of NASA QUDT, which is an OWL ontology of every
unit NASA has ever dreamed of using, based on a
fundamental ontology that mirrors ISO 80000 and
the International Vocabulary for Measures (VIM).
So, it may be possible that these desired “common
units” have the form:</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
urn:iso:std:iso:15926:-4:tech:class:INCHES_PER_SECOND
</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">or
something the like. It is definitely the intent
of WG3 that they will have a URI</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">
<a moz-do-not-send="true"
href="http://iso.org/std/iso/15926/-4">http://iso.org/std/iso/15926/-4#</a>
INCHES_PER_SECOND</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">or
something the like (and that is only because W3C
decided that http: is the universal prefix for
IRIs, and no longer denotes a protocol). But WG3
would really prefer that QUDT was a referenceable
standard in its own right, with its own IRI path.</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">With
the above as background, it is important for SC4
to avoid participating in the construction of
another cottage industry. It would be a “good
thing” for SC4 to bring its interested parties to
a common table and come up with a common solution
to this problem for SC4 specifications, instead of
one-off conventions for the favorite technology of
each Working Group.
</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">-Ed</span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"> </span><o:p></o:p></p>
<div style="border:none;border-left:solid blue
1.5pt;padding:0in 0in 0in 4.0pt">
<div>
<div style="border:none;border-top:solid #B5C4DF
1.0pt;padding:3.0pt 0in 0in 0in">
<p class="MsoNormal"
style="text-autospace:ideograph-other"><b><span
style="font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-family:"Tahoma","sans-serif";color:windowtext">
wg11 [<a moz-do-not-send="true"
href="mailto:wg11-bounces@steptools.com">mailto:wg11-bounces@steptools.com</a>]
<b>On Behalf Of </b>Martin Hardwick<br>
<b>Sent:</b> Tuesday, June 10, 2014 10:22 AM<br>
<b>To:</b> Thomas Liebich; wg11<br>
<b>Subject:</b> Re: [wg11] Minutes of Part
21 E3 DIS testing telecon on June 5, 2914</span><o:p></o:p></p>
</div>
</div>
<p class="MsoNormal"> <o:p></o:p></p>
<div>
<p class="MsoNormal">Hi Thomas,<br>
<br>
Thanks for this feedback.<br>
<br>
I am growing in favor of using a simple URN for
all the "famous" (well known units).<br>
<br>
Hence, we might have in the reference section of
a P21 e3 file:<br>
<br>
#10=<urn:iso:metre>;<br>
#20=<urn:iso:inch>;<br>
#30=<urn:iso:centigrade>;<br>
#40=<urn:iso:Fahrenheit>;<br>
#50=<urn:iso:furlong> ;<br>
#60=<urn:iso:inches-per-second>;<br>
<br>
And so on for all the units that the standards
want to recognize. There would not need to be
any files to define these units (but there could
be). Software systems would be expected to
"know" them from the URN and that would include
knowing how to convert between them. <br>
<br>
(Without benefit of a conversion based
expression - oh my gosh what will happen if
there is an apocalypse and the only people left
are idiot savant nerds who only know how to
follow mathematical expressions and cannot
remember any units except the ones stored in the
NIST library which was the only building in
Washington to survive the catastrophe of course)
- Yes I will be made to regret this statement.<br>
<br>
Martin<br>
<br>
<br>
On 6/10/2014 9:29 AM, Thomas Liebich wrote:<o:p></o:p></p>
</div>
<blockquote
style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal" style="margin-bottom:12.0pt">Dear
all,<br>
<br>
only as a side remark. During our IFC (ISO16739)
developments we faced the same issue - a derived
unit involving factor and offset cannot be
defined with the current conversion_based_unit.<br>
<br>
So we added a subtype to IFC4, which essentially
defines the same, as the proposed extension here
for P41.<br>
See <a moz-do-not-send="true"
href="http://www.buildingsmart-tech.org/ifc/IFC4/final/html/link/ifcconversionbasedunitwithoffset.htm">http://www.buildingsmart-tech.org/ifc/IFC4/final/html/link/ifcconversionbasedunitwithoffset.htm</a><br>
<br>
One important consideration: you need to
determine, whether to apply the offset before or
after applying the factor. We decided to apply
it after.<br>
<br>
hope it gives another insight,<br>
<br>
regards<br>
Thomas<br>
<br>
-- <o:p></o:p></p>
<div>
<p class="MsoNormal">Am 08.06.2014 01:46,
schrieb thomas thurman:<o:p></o:p></p>
</div>
<blockquote
style="margin-top:5.0pt;margin-bottom:5.0pt">
<p class="MsoNormal">Addendum for Fahrenheit
discussion. <o:p></o:p></p>
<div>
<div>
<p class="MsoNormal">Comments on current
approach in part 41 and AP 214:<o:p></o:p></p>
<div>
<div>
<div>
<p class="MsoNormal">1-part 41 is
specific that any unit that is
related to a unit specified in part
41 shall be a
‘conversion_based_unit’.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">2-conversion_based_unit
only converts the magnitude but does
not provide an offset.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">3-The use of ISO
13584-20 for such a simple case is
long agreed overkill; the example in
part 41 F 4.4 has EXPRESS<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">errors (<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">a-the
expression_conversion_based_unit
shall be a conversion_based_unit
(see (1) above.) and<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">b-the attribute
redeclaration in e.g.,
named_unit_variable.associated_variable_environment
is invalid.).<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">4-AP 242 ed1 did
not include a structure to support
Fahrenheit unit exchange.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">5-AP214 used a
context_dependent_unit which is
invalid (see (1) above). As noted
above this was NOT promoted to<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">AP 242.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">6-After several
attempts to discover a URL,URN for
Fahrenheit I gave up and am
proposing that SC4 define its own<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">(NIST has a guide
that includes a definition of
Fahrenheit as a note (I think) but
does not provide a URN or URL.).<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">(There are
multiple conversion calculators on
the web but I am not convinced of
their persistence.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">In any event use
of a conversion calculator opens up
its own can of worms.)<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">==========proposed
solution:===========<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">add a subtype of
conversion_based_unit,
conversion_based_unit_with_offset to
provide the offset.<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">=========current:============<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:13.5pt;font-family:"Times","serif"">A <b>conversion_based_unit</b> is
a type of </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.named_unit"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">named_unit</span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif""> that
defines a unit on the basis of a </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">measure_with_unit</span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif"">.</span>
<o:p></o:p></p>
<p class="note"><a
moz-do-not-send="true"
name="note_"><span
style="font-family:"Times","serif"">NOTE </span></a><span
style="font-family:"Times","serif""> The <a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit.value_component"><b>value_component</b></a> attribute
of the <a moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit"><b>measure_with_unit</b></a> defines
the conversion factor.</span><o:p></o:p></p>
<p class="example"><a
moz-do-not-send="true"
name="example_"><span
style="font-family:"Times","serif"">EXAMPLE
An inch is a <b>conversion_based_unit</b>.
It is from the Imperial system,
its name is "inch", and it can
be related to the </span></a><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.si_unit"><b><span
style="font-family:"Times","serif"">si_unit</span></b></a><span
style="font-family:"Times","serif"">, millimetre,
through a </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit"><b><span
style="font-family:"Times","serif"">measure_with_unit</span></b></a><span
style="font-family:"Times","serif""> whose value is
25.4 millimetre. A foot is also a <b>conversion_based_unit</b>.
It is from the Imperial system,
its name is "foot", and it can be
related to an </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.si_unit"><b><span
style="font-family:"Times","serif"">si_unit</span></b></a><span
style="font-family:"Times","serif"">, millimetre,
either directly or through the
unit called "inch".</span><o:p></o:p></p>
<div>
<p class="MsoNormal"><u><span
style="font-size:13.5pt;font-family:"Times","serif"">EXPRESS
specification:</span></u><o:p></o:p></p>
</div>
<p><code><span
style="font-size:10.0pt">*)</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code>ENTITY conversion_based_unit</code><br>
<code> SUBTYPE OF (</code></span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresource_docs%5Cfundamentals_of_product_description_and_support%5Csys%5C18_schema.htm#measure_schema.named_unit"><span
style="font-size:10.0pt;font-family:"Courier
New","serif"">named_unit</span></a><code><span
style="font-size:10.0pt">);</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code> name : </code></span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresource_docs%5Cfundamentals_of_product_description_and_support%5Csys%5C25_schema.htm#support_resource_schema.label"><span
style="font-size:10.0pt;font-family:"Courier
New","serif"">label</span></a><code><span
style="font-size:10.0pt">;</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code> conversion_factor : </code></span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresource_docs%5Cfundamentals_of_product_description_and_support%5Csys%5C18_schema.htm#measure_schema.measure_with_unit"><span
style="font-size:10.0pt;font-family:"Courier
New","serif"">measure_with_unit</span></a><code><span
style="font-size:10.0pt">;</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code>WHERE</code><br>
<code> WR1:
SELF\named_unit.dimensions =
derive_dimensional_exponents(conversion_factor\measure_with_unit.unit_component);</code><br>
<code>END_ENTITY;</code><br>
<code>(*</code></span><o:p></o:p></p>
<p><u><span
style="font-size:13.5pt;font-family:"Times","serif"">Attribute
definitions:</span></u><o:p></o:p></p>
<p class="expressdescription"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">name: </span></b><span
style="font-size:13.5pt;font-family:"Times","serif"">the </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Csupport_resource_schema%5Csupport_resource_schema.htm#support_resource_schema.label"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">label</span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif""> by
which the <b>conversion_based_unit</b> is
known.</span><o:p></o:p></p>
<p class="expressdescription"><a
moz-do-not-send="true"
name="measure_schema.conversion_based_unit.con"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">conversion_factor: </span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif"">the </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">measure_with_unit</span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif""> that
specifies the physical quantity
from which the <b>conversion_based_unit</b> is
derived.</span><o:p></o:p></p>
<p><u><span
style="font-size:13.5pt;font-family:"Times","serif"">Formal
propositions:</span></u><o:p></o:p></p>
<p class="expressdescription"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">WR1: </span></b><span
style="font-size:13.5pt;font-family:"Times","serif"">The
dimensional exponents shall be
equal to those from the </span><a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.conversion_based_unit.conversion_factor"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">conversion_factor</span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif"">.</span><o:p></o:p></p>
<div>
<p class="MsoNormal"><span
style="font-size:12.0pt"> </span><o:p></o:p></p>
</div>
</div>
<div>
<p class="MsoNormal">=========proposed
addition to part 41=========<o:p></o:p></p>
</div>
<div>
<p class="MsoNormal"><span
style="font-size:13.5pt;font-family:"Times","serif"">A <b>conversion_based_unit_with_offset</b> is
a type of <b>conversion_based_unit</b> that
includes a scale offset.</span><o:p></o:p></p>
</div>
<div>
<p class="note"><span
style="font-size:13.5pt;font-family:"Times","serif"">EXAMPLE
A Fahrenheit is a <b>conversion_based_unit_with_offset</b>.
It is from the Imperial system,
its name is “fahrenheit", and it
can be related to the <a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.si_unit"><b>si_unit</b></a>,
degree Celsius, through a <a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresources%5Cmeasure_schema%5Cmeasure_schema.htm#measure_schema.measure_with_unit"><b>measure_with_unit</b></a> whose
value is 1.8 degree Celsius. The
offset is 32 degree Celsius.</span><o:p></o:p></p>
<p><u><span
style="font-size:13.5pt;font-family:"Times","serif"">EXPRESS
specification:</span></u><o:p></o:p></p>
<p><code><span
style="font-size:10.0pt">*)</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code>ENTITY
conversion_based_unit_with_offset</code><br>
<code> SUBTYPE OF (</code></span><code><b><span
style="font-size:10.0pt;font-family:"Times","serif"">conversion_based_unit</span></b></code><code><span
style="font-size:10.0pt">);</span></code><span
style="font-size:10.0pt;font-family:"Courier
New","serif""><br>
<code> offset : <a
moz-do-not-send="true"
href="file:///%5C%5C%5C%5CUsers%5Ctom%5CDocuments%5C2013%5CSMRLv5%5CSMRL_v5_rc5%5Cdata%5Cresource_docs%5Cfundamentals_of_product_description_and_support%5Csys%5C18_schema.htm#measure_schema.measure_with_unit">R</a>EAL;</code><br>
<code>WHERE</code><br>
<code> WR1: offset <> 0.0;</code><br>
<code>END_ENTITY;</code><br>
<code>(*</code></span><o:p></o:p></p>
<p><u><span
style="font-size:13.5pt;font-family:"Times","serif"">Attribute
definitions:</span></u><o:p></o:p></p>
<p class="expressdescription"><a
moz-do-not-send="true"
name="measure_schema.conversion_based_unit.nam"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">offset: </span></b></a><span
style="font-size:13.5pt;font-family:"Times","serif"">the value
of the offset represented in the
units of the conversion_factor
inherited from
the conversion_based_unit.</span><o:p></o:p></p>
<p class="expressdescription"><u><span
style="font-size:13.5pt;font-family:"Times","serif"">Formal
propositions:</span></u><o:p></o:p></p>
<p class="expressdescription"><a
moz-do-not-send="true"
name="measure_schema.conversion_based_unit.wr:"><b><span
style="font-size:13.5pt;font-family:"Times","serif"">WR1: The
offset shall not be zero.</span></b></a><o:p></o:p></p>
<div>
<p class="MsoNormal">Note: If the
offset is zero, then the
supertype <b><span
style="font-family:"Times","serif"">conversion_based_unit
</span></b><span
style="font-family:"Times","serif"">is
used.</span><o:p></o:p></p>
</div>
</div>
<div>
<div>
<p class="MsoNormal">=========end
proposed addition to part
41=========<o:p></o:p></p>
</div>
</div>
<div>
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div>
<p class="MsoNormal">On Jun 6, 2014,
at 3:29 PM, Martin Hardwick <<a
moz-do-not-send="true"
href="mailto:hardwick@steptools.com">hardwick@steptools.com</a>>
wrote:<o:p></o:p></p>
</div>
<p class="MsoNormal"><br>
<br>
<br>
<o:p></o:p></p>
<div>
<div
style="margin-left:-.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-align:center"
align="center"><b><span
style="font-size:16.0pt">P21
e3 DIS Testing</span></b><o:p></o:p></p>
</div>
<div
style="margin-left:-.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-align:center"
align="center"><span
style="font-size:14.0pt">Minutes
of June 5, 2104 Telecon</span><o:p></o:p></p>
</div>
<h2>Attendees<o:p></o:p></h2>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Martin
Hardwick
<a moz-do-not-send="true"
href="mailto:hardwick@steptools.com"><hardwick@steptools.com></a>
<br>
Robert Lipman <a
moz-do-not-send="true"
href="mailto:robert.lipman@nist.gov"><robert.lipman@nist.gov></a>
<br>
Michael Benda <a
moz-do-not-send="true"
href="mailto:mjbenda@rockwellcollins.com"><mjbenda@rockwellcollins.com></a>
<br>
Hedlind Mikael <a
moz-do-not-send="true"
href="mailto:mikael.hedlind@scania.com"><mikael.hedlind@scania.com></a>
<br>
Dave Loffredo <a
moz-do-not-send="true"
href="mailto:loffredo@steptools.com"><loffredo@steptools.com></a>
<br>
Ed Paff <a moz-do-not-send="true"
href="mailto:ejp@transcendata.com"><ejp@transcendata.com></a>
<br>
Tom Thurman <a
moz-do-not-send="true"
href="mailto:thomas.r.thurman@imonmail.com"><thomas.r.thurman@imonmail.com></a><o:p></o:p></p>
<h2>Apologies for Absence<o:p></o:p></h2>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Jochen
Fritz
<a moz-do-not-send="true"
href="mailto:jfritz@steptools.com"><jfritz@steptools.com></a>
<o:p></o:p></p>
<p class="MsoNormal"
style="mso-margin-top-alt:auto;mso-margin-bottom-alt:auto">Nicolas
Figay
<a moz-do-not-send="true"
href="mailto:nicolas.figay@eads.net"><nicolas.figay@eads.net></a>
<br>
<br>
<br>
<o:p></o:p></p>
<h2>PMI Splitting<o:p></o:p></h2>
<p class="htmlbody">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:<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><a
moz-do-not-send="true"
href="ftp://www.steptools.com/private/P21e3_DIS_testing/PMI/">ftp://www.steptools.com/private/P21e3_DIS_testing/PMI/</a><o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">STEP Tools is
sponsoring the development of open
source programs to split and merge
P21 files using the Edition 3
specification. The programs are
available at the following URL:
<a moz-do-not-send="true"
href="http://tinyurl.com/thundercode">http://tinyurl.com/thundercode</a>.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<h2>ZIP Assemblies<o:p></o:p></h2>
<p class="htmlbody">No visible
progress has been made on this test
case since the last telecom, but the
PMI merge and split code is being
updated to handle this case as well.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><a
moz-do-not-send="true"
href="ftp://www.steptools.com/private/P21e3_DIS_testing/ZIP_Assembly/">ftp://www.steptools.com/private/P21e3_DIS_testing/ZIP_Assembly/</a><o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">In the last
telecom:<o:p></o:p></p>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in"><span
style="font-family:Symbol">·</span><span
style="font-size:7.0pt">
</span>We decided the sub-tree
directory names should include the
NUAO identifier(s) for their
corresponding node in the assembly
tree.<o:p></o:p></p>
</div>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in"><span
style="font-family:Symbol">·</span><span
style="font-size:7.0pt">
</span>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.<o:p></o:p></p>
</div>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in"><span
style="font-family:Symbol">·</span><span
style="font-size:7.0pt">
</span>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.<o:p></o:p></p>
</div>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in"><span
style="font-family:Symbol">·</span><span
style="font-size:7.0pt">
</span>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.
<o:p></o:p></p>
</div>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><b> </b><o:p></o:p></p>
<h2>Unit Definitions<o:p></o:p></h2>
<p class="htmlbody">The unit
definitions have been merged into a
single file called units.stp.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><a
moz-do-not-send="true"
href="ftp://www.steptools.com/private/P21e3_DIS_testing/Units/">ftp://www.steptools.com/private/P21e3_DIS_testing/Units/</a><o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">We continued our
discussion on whether unit
references should be encoded as a
URL or a URN. The following two
lines of code show equivalent URL’s
and URN’s.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><a
moz-do-not-send="true"
href="http://standards.iso.org/iso/10303/tech/reference_data/41/si_base_units.stp#METRE"><http://standards.iso.org/iso/10303/tech/reference_data/41/si_base_units.stp#METRE></a>;<o:p></o:p></p>
<p class="htmlbody"><urn:iso:std:iso:10303:-41:tech:unit:metre>;<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<div
style="margin-left:63.0pt;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-63.0pt">Explanation
of URN: <o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">urn
Indicates this URI is a URN,
instead of the more common URL
(http)<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">iso
URN namespace (other examples are
oid, usbn)<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">std
ISO standard <o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">iso
originating organization (other
examples are iec, iso-ies,
iso-cie)<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">10303
STEP standard
<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">-41
part of multipart standard
(hyphens required)
<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in">Tech
associated or embedded resource
defined by committee that created
the standard
<o:p></o:p></p>
</div>
<div
style="margin-left:1.0in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-1.0in"><the
rest> unspecified
-- controlled by committee.<o:p></o:p></p>
</div>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">In the above
example, the URN has small advantage
over the URL but perhaps the
following URN will be acceptable
because a file does not have to
exist to define a URN.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><urn:iso:metre>;<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">It is also
conceivable that the following URN
might be acceptable even though
there are currently small technical
issues stopping the deployment of
unit definitions for a Fahrenheit
measure in a STEP file.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><urn:iso:Fahrenheit>;
<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">We further
discussed the requirements if all
the unit definitions are to be
defined in STEP files. The
definition of literal constants such
as PI, and EXPRESS constants such as
negri_pi, have both led to extensive
additions to the edition 3 format
for which other strong use cases are
currently lacking.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">On the other hand
the problem might be that we have
not been sufficiently ambitious. It
was pointed out that if constants
can be defined then we are close to
allowing expressions to be defined.
The use of the PLIB schema for
expressions has never been very
satisfactory because the expressions
are too hard to read when encoded
into the STEP files. However, if
Part 21 has an expression evaluation
capability (probably in the anchors)
then potential STEP applications
such as parametrics and construction
history might become more tractable.
One interesting possibility might be
to use Modelica as the expression
language.<br>
<br>
<br>
<o:p></o:p></p>
<h2>Digital Signatures<o:p></o:p></h2>
<p class="htmlbody">STEP Tools gave a
demonstration of how to make a
digital signature using a private
key and a signing certificate and
how to verify that a file has not
been edited since it was signed
using a public key.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody"><a
moz-do-not-send="true"
href="ftp://www.steptools.com/private/P21e3_DIS_testing/Digital_signatures/">ftp://www.steptools.com/private/P21e3_DIS_testing/Digital_signatures/</a><o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">We discussed white
space and the issues that might
arise if a file is read into
Notepad/Wordpad and converted from
line-feeds to carriage returns or
vice versa. These characters are
explicitly excluded from the Part 21
character set so they will not be
included when computing and
verifying the hash value.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">We discussed
supporting multiple signatures. The
easiest procedure is for each
signature to be applied to all of
the characters that precede that
signature. Thus each new signee is
also verifying the signature of the
previous signees.
<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<p class="htmlbody">For this to be
consistent it would be best if the
signatures came after the
END-ISO-10303-21 keyword as shown in
the example on the ftp site.<o:p></o:p></p>
<p class="htmlbody"> <o:p></o:p></p>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in"><span
style="font-family:Symbol">·</span><span
style="font-size:7.0pt">
</span>The next conference call
will be held on Friday June 27 at
4PM Paris, 3PM London, 10AM New
York and 7AM Seattle.<o:p></o:p></p>
</div>
<p class="htmlbody"> <o:p></o:p></p>
<h2>Action Items<o:p></o:p></h2>
<p class="htmlbody"
style="margin-left:.5in;text-indent:-.25in">1.<span
style="font-size:7.0pt">
</span>Complete the first ZIP
assembly example.<o:p></o:p></p>
<p class="htmlbody"
style="margin-left:.5in;text-indent:-.25in">2.<span
style="font-size:7.0pt">
</span>Consider the best approach
for unit definitions: URN’s or
URLs’?<o:p></o:p></p>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in">3.<span
style="font-size:7.0pt">
</span>Consider if Edition 3
should offer any support to the
definition of parametrics and if
so how?<o:p></o:p></p>
</div>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in">4.<span
style="font-size:7.0pt">
</span>Extend the digital
signatures example to include the
creation of signing certificates.<o:p></o:p></p>
</div>
<div
style="margin-left:.5in;margin-right:-.5in">
<p class="MsoNormal"
style="text-indent:-.25in">5.<span
style="font-size:7.0pt">
</span>Demonstrate signing at one
site (ITI) and verification at
another site (STEP Tools).<o:p></o:p></p>
</div>
<div
style="margin-left:.25in;margin-right:-.5in">
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<div
style="margin-left:.25in;margin-right:-.5in">
<p class="MsoNormal"> <o:p></o:p></p>
</div>
<p class="MsoNormal"
style="text-autospace:ideograph-other">As
recorded by Martin Hardwick
<a moz-do-not-send="true"
href="mailto:hardwick@steptools.com"><hardwick@steptools.com></a>
<br>
<br>
<br>
<o:p></o:p></p>
</div>
<p class="MsoNormal"
style="text-autospace:ideograph-other"><span
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<p>beste Grüße / kind regards<br>
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<p><span style="font-size:10.0pt">AEC3
Deutschland GmbH<br>
AG München, Handelsregister HRB
164221<br>
Geschäftsführer: Dr. Thomas Liebich,
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