Planning Systems

Abstract One of the major obstacles to the use of planning systems has been the difficulty of acquiring descriptions of how tasks are carried out in particular environments. In order to address this problem, the authors propose a visual language for the acquisition, display and debugging of this plan knowledge. The basis of this language is a model of the user's view of tasks, supported by a series of psychological experiments. DACRON supports the acquisition of plan knowledge by providing graphical representations of domain entities ...

Maxillofacial surgery treats abnormalities of the skeleton of the head. Skull remodelling implies osteotomies, bone fragment repositioning, restoration of bone defects and inserting implants. In this field there is a huge demand from the surgeons to be able to predict the new facial outlook after surgery. Besides the big interests for the surgeon during planning, it is also an essential tool to improve the communication between surgeon and patient.Mass Spring Models (MSM) are widely used to simulate the deformation behavior of soft tissues. The usage of these models has however some serious disadvantages. Most important is that the MSM has no real bio-mechanical foundation. The Finite Element Model (FEM) on the other hand has a strong bio-mechanical foundation but the high computational cost and a difficult architecture make it not very useful for fast simulators. In this paper we present the usage of a Mass Tensor Model (MTM) to simulate the soft tissue deformations after bone displacement. This model tries to combine the advantages of FEM and MSM. Moreover by combining this MTM with a new static solution scheme and a dynamic threshold, we were able to reduce the calculation time seriously when compared to MSM or FEM.