A knowledge-navigation system for dimensional metrology

Journal of Research of the National Institute of Standards and Technology, March-April, 2002 by Howard T. Moncarz

A compilation was made of all of the possible interfaces in the dimensional-inspection process, and an assessment was made of the standards in place or under development to satisfy those interfaces (5). Figure 1, from Ref. (5), shows the processes and information exchanges that were identified. (Note that active interfaces are defined as command-status interfaces in the reference.) The assessment indicated a large tangle of standards that included redundancies and conflicts where the domains of multiple standards overlapped and gaps where there was no coverage at all.

A large store of information is contained in and associated with the compilation and assessment in Ref. (5). It is important to have a clear understanding of that information and its nuances, e.g., why certain information items are specified in certain standards but not in others that seemingly overlap the same processes. The assessment is large and complex and difficult to present clearly, particularly in the static format of a report. However, a clear communication of the assessment would help industry to prioritize its resources (along with government and academia collaboration) to develop and harmonize the standards required. If that could be accomplished, the market for applications supporting the inspection process could grow more efficiently.

1.3 Problem Summary

Dimensional metrology is an important subject but difficult to master for two main reasons. First, it is based on complex 3D geometric entities and relationships. Second, the geometry is associated with a large, diverse knowledge base that has many interconnections. Understanding the knowledge and the interconnections is necessary to master the subject.

This paper presents an approach to address the problem and describes a prototype system that was created to demonstrate the approach.

2. Solution

The goal is to provide an intuitive feel for different types of tolerances and to allow an intuitive access to a diverse knowledge base of dimensional metrology information. This goal leads to a novel approach that combines several aspects. The main idea is to create a knowledge domain that is organized around a set of key concepts and to represent those concepts as virtual objects that can be navigated with interactive computer visualization techniques.

The approach can be applied to the dimensional metrology domain to enable several applications. First is the application to convey the definition and meaning of GD&T over a broad and comprehensive range of that domain as represented by the Y14.5 standard. Second is the application to provide a visualization of a control hierarchy of the inspection process with links to dimensional metrology knowledge. Third is the application to show clearly the coverage of interoperability standards within the inspection process to enable industry to make intelligent decisions on standards development and harmonization efforts.

A primary challenge is to choose the key concepts wisely, including their representation as virtual objects. They should be as independent from each other as possible and should enable a wide and comprehensive coverage of the subject domain. For the concept to be useful in this approach, its virtual representation needs to comprise a decomposition into sub-concepts that distinguishes among information items in the knowledge base at a sufficient resolution to satisfy the applications needed.