The rise of the Internet has spawned quite a number of new technologies that could be 
put to good use to address long-standing issues in design and development of distributed 
systems. Problem-Solving Environments are prime candidates to benefit from this wealth 
of technological innovation. This paper
presents a high-level architecture for composing, building, scheduling, and 
executing distributed scientific problem-solving applications. A mosaic of emerging 
technologies is woven together in a credible way {XML, CORBA, Java Beans, eta). 
Although only a conceptual design at this point, it shows considerable scope and 
promise. Associating a performance model with each component is a nice idea in an 
object system. Prototype implementations of the Equation Builder and MDS-PSE do not 
go very far in proving the concepts, beyond what others have already accomplished. 
However the discussion of MDS-PSE provides a concise tutorial on distributed 
execution with CORBA objects. Although not much new ground is broken, readers 
should find it useful to see someone paint the entire picture of what a problem-
solving environment might look like if you drew upon the best of the current 
generation of technologies. The component taxonomy is well thought out for today’s 
problems and computing environments.
However, there is an important piece of related work that should really be discussed and 
compared to the Visual Component Composition Environment. In the late 1980s, several 
commercial dataflow visualization systems arose, largely based on ideas first built into 
products by the team that became Advanced Visual Systems, Inc. Although directed at the 
visualization market, AVS tools are actually PSE composition and execution systems (see 
http://www.avs.com/products/). There are strong similarities between AVS and VCCE. The 
AVS system of components, their dataflow paradigm with typed inputs and outputs, and 
their interactive canvas composition system are all very similar to the VCCE design 
described in this paper. Of course, VCCE is an updated design. It would be highly 
desirable to explicitly compare AVS to VCCE in Section 2 of this paper. I think such a 
discussion would also help to highlight some of the innovative points of the VCCE design 
for the readers.
Others have done extensive work within the AVS environment, pushing its limits as a PSE 
composition tool. One of the things that they found was that the pure dataflow model is 
only practical for simple execution structures. For example, when the execution flow 
needed to loop (as in computational steering), getting the connected dataflow 
components to do the right thing became very awkward. AVS eventually added Some control 
mechanisms that ameliorated this problem. A similar problem could occur in the new 
architecture presented in this paper. However, the event model described in this paper 
may provide a way around the pure dataflow model.