Autodesk: The DWG format is already open -- via DXF.
OpenDWG: DXF is not a complete, fully specified, efficient standard.
It is popular because there is nothing else available. The data in the
DWG is more precise than in the DXF file (more decimal places), critical
in a CAD application. Documentation for the ACIS entities is encrypted
in the DXF format.
[The OpenDWG Alliance posted a white paper at
its Web site, which lists a number of reasons why DXF is insufficient as
an exchange format:
http://www.opendwg.org/dxf/index.html
. The Associate OpenDWG Member license is at http://www.opendwg.org/membership/associate.html
-- Ed.]
An observation -- if Autodesk feels that the
DXF format handles all data interoperability needs that DWG users could
conceivably have, why does it offer DWG Unplugged? If DXF does it all,
Autodesk should treat the activities of the OpenDWG Alliance with indifference.
Autodesk: Items that appear missing from DXF are also not present in DWG, such as application- specific data (that's handled by ARx) and OLE objects.
OpenDWG: In DWG, "application specific data" are stored as proxies.
While the format of the data contained within the proxy may be known only
to the vendor who created those entities, it is incorrect to say that the
data is not stored in the file. It could, of course, be that the data stored
in the file refers to data stored outside of it, but that is a different
issue.
Further, this statement does not explain why
ACIS data is encrypted within DXF How does Autodesk suggest that the user
community cope with that?
Also, admittedly a minor point, DXF does not
contain raster preview data.
Autodesk: It's not the DWG data that other CAD vendors have problems with, it's trying to map unique-to-AutoCAD objects (such as the splined polyline) to similar-but-different objects in the destination CAD software.
OpenDWG: Although the issue of translation, unique entities,
and all such is interesting, it is not relevant to what the OpenDWG Alliance
is trying to accomplish; that is, to promote DWG as an open CAD drawing
exchange standard. The above issue is true for DXF as well, but DXF is
an inadequate exchange standard.
By focusing exclusively on competitive positioning,
Autodesk's response fails to take into consideration how _users_ may wish
to get access to their own data using their own tools. The OpenDWG Alliance
is addressing this right now.
Autodesk: We are already involved in ten open data exchange standards: DXF, IGES, IAI, IFC, AutoCAD OEM, PDES, STEP, DWF, OGC, and OLE for D&M.
OpenDWG: This is all commendable; however, AutoCAD OEM is not
and cannot be considered an "open data exchange standard." DXF has serious
shortcomings. DWF, while useful in the Web environment, strips a large
amount of the intelligence from the drawing data and thus cannot be considered
a "data exchange standard." Some of the initiatives listed above have been
glacial slow in promoting interchange standards that have concrete, tangible
benefits for CAD users.
Lastly, none of the above "open data exchange
standards" represent 2,000,000,000 legacy drawings out among the user community
like DWG does. To paraphrase Willie Sutton, if you're going to promote
data exchange, you have to go where the drawings are.
Autodesk: By forming this alliance, Visio is admitting that IntelliCAD is _not_ 100% compatible with AutoCAD; Autodesk sees this as an admission by Visio that they need help from 14 other companies in decoding DWG.
OpenDWG: This assessment is flawed. We should be certain we are
a making distinction between the OpenDWG Toolkit and IntelliCAD 98 by Visio.
The OpenDWG Toolkit is the most comprehensive third-party reconstruction
of DWG now available.
By admission, the Toolkit is not 100% complete;
that level of knowledge is reserved to Autodesk, and Autodesk could put
this issue to rest immediately by publishing the DWG specification, or
even by widely offering DWG Unplugged.
Since they have declined to do either, the OpenDWG Alliance must move
forward with what _is_ known, and hope to improve upon it.
When it was owned by MarComp, the AUTODIRECT
toolkit was on the market for over ten years with hundreds of satisfied
licensees; one would assume it was doing a good job as far as its users
were concerned. Matt Richards, former president of MarComp, estimates the
OpenDWG Toolkit presently covers 95% to 99% of the make-up of the DWG format.
In his opinion, the parts of the file format
that the Toolkit presently doesn't completely understand represent some
form of "housekeeping" data that has nothing to do with drawing make-up,
the entity data, the geometry, or anything else in the CAD file that matters
to the user. Right now, when the Toolkit writes data into DWG representing
those unknown areas, it uses place holder values that are "known good"
within AutoCAD.
Still, if other Alliance members can contribute
knowledge of what the "odd byte pair here and there" stands for, it only
helps the alliance's understanding of DWG, moving it nearer to 100%.
The OpenDWG Alliance is not about Visio vs.
Autodesk. It's about fifteen CAD vendors joining together to provide tools
to help users leverage their present investment in their own drawings.
In doing that, DWG is strengthened as a format for encapsulating valuable
drawings, and it's unclear how Autodesk could hurt by that.
Autodesk: We chuckle at the thought of SolidWorks and PTC sharing information with each other.
OpenDWG: It is unfortunate that Autodesk appears to miss the point and seems unwilling to look past the superficial competitive issues. It's not about PTC versus SolidWorks; it's about providing better software to DWG owners to help them leverage the drawings _they_ own. It is in both SolidWorks' and PTC's interest to give DWG users the best possible quality tools for working within the DWG environment.
Autodesk: Why we should open up DWG when companies like Visio and PTC have not done the same with their VSD and Pro/E file formats.
OpenDWG: The requirement to publish a file format arises when
that format becomes a de facto industry standard -- where it is virtually
impossible to do business without supporting it, and when there is user
and developer demand for such support.
With over two billion DWG files in existence,
the DWG file is currently the de facto CAD industry standard for encapsulating
measured drawings. USA government contracts often specify that drawings
be delivered in the DWG format.
When another CAD file format becomes an industry standard on the level
that DWG has, the OpenDWG Alliance expects that users and vendors will
also call for that file format to be documented as well.
Visio presently does not have anywhere near
the number of legacy drawings stored in VSD format as Autodesk has with
the DWG format.
Still, tools are now available for users of
VSD files to utilize Visio drawings within other software products.
INSO Corporation is presently selling development tools to its licensees
that provide import capabilities for VSD.
Micrografx products and the products of other business diagramming
vendors import VSD format into their own applications.
Visio does not feel it necessary to run a
"100% Pure Visio VSD" campaign [such as Autodesk's "100% Pure AutoCAD DWG"]
to attempt to fend off "unauthorized" exchange of drawing formats. All
that being said, Visio is presently taking steps that will further enhance
unrestricted access to the value contained within VSD files.
First and foremost, let me re-iterate our stance on who we think the
"data" belongs to -- it belongs to the customer. The Alliance earnestly
wants to position OpenDWG as a noble endeavor but it remains an opportunistic
alliance of competitors looking to reverse engineer our R&D [research
and development] and intellectual property.
Along with the geometric data, DWG contains
several enhancements (i.e. our intellectual property) such as compression,
performance enhancements, data corruption protection, etc. This represents
our added value to the core data, and is a separate issue from interoperability.
We believe that customers have a fundamental
right to interoperate with other products, which is why we invented DXF,
and participated in the STEP, IGES, and IAI efforts, which are aimed at
fundamentally solving the data interoperability problem across a whole
range of design applications.
An excellent analogy here can be drawn with
the Microsoft Word .DOC file format (which is proprietary) and the Rich
Text Format intended to interoperate between Windows word processors. There
are certainly more than two billion DOC files on the planet. There's also
more data stored in proprietary Oracle, Informix, DB/2 and Sybase formats
with a standard access mechanism (SQL). ["It is Microsoft's practice
to license the Word 97 DOC format to other ISVs, including competitors,
for import and Save As purposes." -- Rob Curran, OpenDWG Alliance.]
Ours is stored in DWG, accessible via our
APIs and via DXF. Very few serious graphics programs may store their data
in GIF format, but all import/export it. Our import/export format is DXF.
We are looking forward to the day that any of the vendors in the OpenDWG
alliance have their native data in open formats.
The Alliance points out some "suspected" areas of
differentiation between DXF and DWG:
OpenDWG: DWG is more compact than DXF.
Autodesk: This is true; this goes back to the value-added- compression we carry out. DXF can be saved in binary mode, which takes up less space.
OpenDWG DWG is more precise than DXF.
Autodesk: DXF can be saved in 16-bit binary mode, in which floating point values are written with the same level of precision as they are written in DWG
OpenDWG: ACIS is encrypted.
Autodesk: It's true that the data is in SAT format encrypted in DXF; it's also encrypted in DWG. ["The data encryption in the SAT format is merely a bit swap. It was put in more as a warning that this format might change (it's controlled by Spatial Technologies) rather than to hide the data. After all, if the group can successfully reverse-engineer binary DWG files, I am certain it is technically competent to discover a mere bit-swapping." -- Carl Bass, Autodesk]
OpenDWG: Proxy data is incomplete.
Autodesk: DXF and DWG contain the same level of information
about proxy objects. So if the DXF file is considered informationally incomplete,
the DWG file is just as incomplete. In the world of object-oriented programming,
code _and_ data are needed. Data alone isn't enough.
OpenDWG: Preview image is missing.
Autodesk: It is omitted out of DXF. ["It can be reconstructed from the data. Our aim is to ensure there is no loss of information when customers move their data, regardless of format." -- Carl Bass]
OpenDWG: What is the need for DWG Unplugged?
Autodesk: The idea behind DWG Unplugged is not to enable "DWG reading" but rather to solve a class of customer problems, which involve displaying graphical data without need for a CAD application. Parts catalogs and sales force automation are examples of such customer problems.
OpenDWG: Requiring DXF files means they may not be the same version as the DWG file (synchronization and version control).
Autodesk: We have the same synchronization issue with DWF as with DXF. A few approaches here could work: redefining the SAVE command in AutoCAD or using Autodesk View or AutoCAD LT in conjunction with a script file in batch mode on a set of drawings to do the DWG-DXF conversion. In the future, we expect to solve these problems through intelligent "design servers" that can serve up data in the format most accessible to the querying client application.
In closing, I do want to say that we are treating the efforts of OpenDWG
with indifference. We find the attention placed on DWG rather flattering,
but misplaced. We believe that we are solving the problem of getting data
in and out of various CAD programs by supporting DXF and IGES, and that
the industry needs to solve much larger problems of lifecycle management,
process integration, etc. via the STEP and IAI efforts.
OpenDWG is a great marketing tactic, but it
is _not_ a serious attempt to solve real customer problems. It is mainly
a marketing tactic. There's some pretty closed thinking behind the OpenDWG
alliance.