The development of modeling tools within the context of future open co
mputer-aided process engineering environments requires careful conside
ration of tool integration strategies such that the modeling process i
s optimally supported, and the resulting models achieve their full usa
ge potential. We differentiate between five kinds of tool integration,
describe the kinds of integration offered by existing process enginee
ring environments, and thereby identify the major shortcomings of curr
ent approaches. To indicate a possible solution to these shortcomings
we sketch the tool integration approach realized in PRO-ART/CE, a prot
otypical process engineering environment.