This project compiled good practice GD&T rules from various sources and implemented them in an advisory system. Some of the rules are shop specific and need to be customized to reflect the availability of various equipment in the particular shop. GD&T rules are good practices from manufacturing and inspection viewpoints only and do not encapsulate part functionality. The advisory system purports to detect and avoid invalid tolerancing specifications and also to help designers make good decisions during the specification stage. This work involves the implementation of an architecture or a seamless integration of solid modeling, dimension and tolerance specification and validation, and tolerance allocation modules. The GD&T system is capable of retrieving selected distance and angle constraints from the constraint graph in the CAD system and adding them to a dimensioning scheme. Good practice rules for GD&T were compiled and implemented in the system. Suggestions, such as equivalent datums that are better from a manufacturing and inspection viewpoint, are proactively provided by the system throughout the specification stage, a unique feature found in this system. The generic DRF category is determined every time datums are selected in a specification. The DRF is evaluated for correctness and appropriateness from manufacturing and inspection viewpoints. A viewer for the visualization of incremental construction of D&T graphs was developed. This viewer guides the designer during the specification of a dimensioning scheme. Three dimensional tolerance maps are generated from data extracted from the global model. Additionally, tolerance values are suggested for intermediate entities in a stack-up obtained from the comparison of functional and accumulation maps. Algorithms for the automatic extraction of dimension loops (Dloops) and stack-up chains for use in downstream applications like tolerance allocation and analysis were developed and implemented.