Re: Will the UML ever become truly universal?

Responding to Nameless...

Which brings me back to the (provocative) subject line.
Surely it is lack of interoperability that prevents UML
from being truly universal? From a user's perspective the
answer to that question must be yes. If I spend (a lot of)
time in an independant UML tool or a programming language
which has an integrated UML tool, it would surely not be
unreasonable of me to expect to export and import my work
(model) into another tool or comparable programming language
--regardless of vendor or programming language (C++ to Ada,
for example). Besides, a product may be unavailable on
certain system platforms. Clearly this is more than a
matter of freedom of choice, however important that may be.

IMHO, interoperability should be a requirement of the UML
specification, for without it the universality of UML is
severly hampered.

I think there is some confusion here about how UML, XMI, and MDA are related to each other and to interoperability.

First, UML and XMI are apples and oranges that are completely different standards. UML is an object-based solution modeling notation (it used to be object-oriented but OMG is broadening the scope) while XMI is essentially a data interchange notation, albeit with heavy conceptual emphasis.

Second, both are notations, not tools. Interoperability is only relevant to the tools that are based on those notations. (Note that the quoted author recognizes this by indicating the the current poor implementations of XMI-based tools is "incomprehensible".)

Third, XMI is only one possible implementation for executing model transformations. While it is enormously convenient to standardize on a single transformation mechanism for plug & play tool developers, there is nothing inherent in UML that ties it to XMI. In fact, translation tools were doing complete, unambiguous transformations based on UML long before XMI, MDA, or even OMG existed.

Fourth, UML and XMI are related through OMG's MDA initiative, which is largely focused on tool interoperability. The MDA initiative has been plugging holes in UML (e.g., an abstract action semantics and execution model), ensuring consistency through introducing the notion of Profiles, and providing a standardization framework around meta models. One of the MDA initiatives happens to be XMI to support model transformation. But XMI is a very recent innovation compared to UML so it has less semantic stability.

As for the rest of your concerns, most of the existing tools for model transformation were based on translation (automated transformation of OOA models into 3GL code or Assembly). Those tools predated XMI, MDA, and, in some cases, OMG itself. As a result the tools tended to be monolithic and highly proprietary. Because MDA is so new, there has been little time to evolve true Plug & Play tools of comparable complexity. However, with supporting "backplane" infrastructures like Eclipse that are designed around MDA, I fully expect a flood of such tools to start appearing over the next couple of years.

<vendor plug>
I might also point out that Pathfinder's PathMATE is plug & play in the sense that it will work with any UML drawing tool that is MDA-compliant and has an XMI repository interface. In addition, the OTS PathMATE can currently do full transformations of the same UML OOA model into C, C++, and/or Java, without any change to the model. In addition, supporting other target languages, including Assembly, or even MS Word (for documentation) is a relatively simple task (Pathfinder just hasn't gotten around to it because of lack of demand).
</vendor plug>


*************
There is nothing wrong with me that could
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H. S. Lahman
hsl@xxxxxxxxxxxxxxxxx
Pathfinder Solutions  -- Put MDA to Work
http://www.pathfindermda.com
blog: http://pathfinderpeople.blogs.com/hslahman
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