CIS/2 file format

[dfitzpatrick]

Although I've been to several seminars that have included a case study
about sharing data between analysis programs and BIM with CIS/2 files
to fabricators, they seem to imply the sharing was started very early
in the design. To the best of my knowledge, no one has implemented
(either on the 'from' side or the 'to' side) any way of tracking
changes through a CIS/2 file. That tells me there was an early dump of
information to get the ball rolling but everything after that had to
be commuicated through 2D plan drawing addendums or maybe some form of
model merge with new CIS/2 data that wasn't discussed.

I started a conversation with Bentley and DesignData about this a
while ago. The key is to have a unique ID that can be maintained by
one application (presumably the BIM model) and tracked by another
(presumably the detailing software). Each time a CIS/2 file is
created, the unique ID (which is a must for associativity in the BIM
models) would be shuttled along through the CIS/2 file. Any of the
detailing softwares could read that unique ID and check against
previous information sent for that element and track it's changes.

As I understand it (not being a software developer), the current
schema for CIS/2 has a location for an element ID however it's a 32
bit integer and MicroStation (for one) uses 64 bit integers for their
unique element IDs. I think there is also a free-form type label that
could be used instead but that seems a bit awkward and difficult to
enforce.

So, I guess my question/comment would be to adjust the element ID to a
64 bit integer (or something else that can accommodate future growth)
or 'agree' on a location in the schema where this 'number' could be
placed that everyone agrees to. I would guess changing the 32 bit to
64 bit might take an act of congress but the 'text label' alternative
seems a bit loosy-goosy.

Any thoughts? Other ideas that could be implemented to enable
'updating' through the CIS/2 file format?
D

[Robert Lipman]

Doug,

CIS/2 does provide for "tracking changes through a CIS/2 file" with
the MANAGED_DATA entities. Those entities assign a Globally Unique ID
(GUID) to parts in the CIS/2 file. The GUID is a 32 character string
that is generated by the CAD application and uses an algorithm that is
used across many applications.
http://en.wikipedia.org/wiki/Globally_Unique_Identifier

To use something other than the GUID, such as a "64 bit integer" would
require either changing CIS/2 or using what's there now such as the
software implementers agreeing to use an entity such as ITEM_PROPERTY.

BTW, a long time ago there was discussion amongst some of the software
vendors to implement MANAGED_DATA to keep track of changes. Nothing
was ever implemented. There are also old tutorials related to '"Data
Management" and "DMC" at Georgia Tech http://www.arch.gatech.edu/~aisc/index.php?cat1=3&cat2=1

This would be a great topics to discuss at a CIS/2 technical workshop.

---
Bob Lipman
http://cic.nist.gov/lipman/


On Oct 7, 1:50 pm, dfitzpatrick <dfitzpatr...@fegstructural.com>
wrote:

[TwH]

D, I think choosing the 32 bit/64 bit element ID is o.k., but in
reality most of the data schemes end up in human-readable format, so
it may be better to allow say 20 characters, which is more consistent
with detailing naming conventions in software. You do bring up a good
point, though, and the industry is moving toward "objects" such as
steel sticks (e.g. the 3D model) that can hold buckets of information
through attachment of other objects (such as connection info) or just
data (such as paint, fire-proofing, or sequence)

On Oct 7, 11:50 am, dfitzpatrick <dfitzpatr...@fegstructural.com>
wrote: