Institute of Computer-aided Product Development Systems

Conceptual Design and Development of a Pro-active Semantic CAD-System

D. Roller , S. Opletal

A pro-active semantic CAD system has a high potential to considerably simplify design activities and hence to shorten development cycles.
In a semantic CAD system, the design activities are supported by special design commands which aid to automate the design task as much as possible. To achieve this, the design phase is pro-actively evaluated and analyzed in the background to provide suitable hints, geometry or other knowledge to the user.
The cycle to process the knowledge, which always runs in the background, focuses on the steps of searching, interpretation, transformation and application of knowledge or geometry. The biggest difficulty lies within evaluating the relevance of information which has to be done within the given task and the current working environment.
align="left"> The process of a knowlegdebased design activity is shown in the following picture:

As a result of the multitude of different information a unified data-model is needed, which can store this highly heterogeneous information.
The semantic CAD component which is running in the background of the CAD system should be able to actively interact with the design process as the designer works on it and should provide him with specialized commands.
Another important aspect is the mediation between several designers working in parallel or one after another on the same or similar objects. The reuse of knowledge and the avoiding of duplicate or unnecessary design steps are of high importance.
Common objectives during the design phase are:

• Connecting objects through geometry
• Deleting objects with a special intent
• Integration of new objects into an existing arrangement
• Adaptation of a design according to guidelines

The two main components that have to be integrated into the CAD system and which will interact with the design process are the semantic user-interface and the knowledge processor.

Semantic User-Interface
The semantic user-interface should enable the user to communicate the design intention on a highly abstract level, where the aim is more important than the actual realization.
The semantics of the design methods will be oriented on the most common design objectives to support them. The application of such a semantic method is analogue to the conventional design methods of the CAD systems. Instead of linking two components through the input of additional geometry, the semantic connection method is applied which covers the intent and tries to come up with a proposal of linking geometry, that the user can accept or modify.
This is achieved by using feature-based approaches that are augmented by dynamic knowledge to provide suitable solutions according to the current design context.

Concept definition in the Active Semantic Network

Knowledge Processor
The knowledge processor will contain a knowledge base that enables the semantic annotation of all elements of a design. It integrates evaluation and searching algorithms that can analyze an ongoing design process and match it against the knowledge already stored. The main focus lies on the organization, access and retrieval of the knowledge. The advantage of knowledge based systems is the support to solve complex problems by the application of intelligent methods. Knowledge based reasoning is a mighty instrument, that can connect data and make it apparent but is also able to generate new knowledge.
In the picture above a concept definition of the active semantic network (developed at IRIS) is shown.
This concept definition has been enhanced to reflect the need to pro-actively support and solve design conflicts. Currently a prototype is in development that will integrate all the components of a semantic design system into the CAD system Autodesk Inventor.