Collaborative systems are distributed multiple-user systems that are both concurrent and synchronized. An interesting research challenge is to develop a collaborative modeling system that offers all facilities of advanced modeling systems to its users, while at the same time providing them with the necessary coordination mechanisms that guarantee effective collaboration. To achieve this, a web-based collaborative feature modeling system, webSpiff, has been developed. It has a client-server architecture, with an advanced feature modeling system as a basis for the server, providing feature validation, multiple views and sophisticated visualization facilities. A careful distribution of the functionality between the server and the clients has resulted in a well-balanced system. On the one hand, the server offers all the functionality of the original feature modeling system. On the other hand, all desirable interactive modeling functionality is offered by the clients, ranging from display of feature model images to interactive model specification facilities. The architecture of webSpiff, the distribution of model data, the functionality of the server and the clients, and the communication mechanisms are described. It is shown that a good compromise between interactivity and network load has been achieved, and that indeed advanced feature modeling with a collaborative system is feasible.
Stereoselective carbon-carbon bond formation via allylic N-sulfonyliminium ionsHopman, J.C.P.; van den Berg, E.; Olero Olero, L.; Hiemstra, H.; Speckamp, W.N.
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Download date: 09 May 2018Pergamon 0(M0-4039(95)00748-2Tetrahedron Letters, Vol. 36, No. 24, pp. 4315-4318, 1995 Abstract: N-Tosyl-6-alkoxy-2,6-dihydro-IH-pyridin-3-ones 1 were found to react stereoselecfively with various nucleophiles under the influence of BF3.OEt2 yielding 2,6-c/s-disubstituted dihydmpyfidinones.
Freeform feature modeling is an extension to feature modeling in which, in addition to regular-shaped features, also freeform features are possible. Due to the large variety of freeform features, a generic approach to specify such features is required. This paper describes such an approach. A freeform feature class is specified by using a prototype and constraints. The latter are used to define intuitive parameters and validity conditions for the class. A new, prototypedriven constraint solving method is used to unambiguously determine a freeform feature during the specification both of a class and of an instance to be added to a model. The specification of freeform features and the prototype-driven constraint solving method are discussed. Several examples are given.
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