||A jigs and fixtures system is a critical device in manufacturing. It provides guidance for tooling and keeps the workpiece at the desired position and orientation in machining processes. It is important to ensure a product satisfying design requirement and to stabilize the product quality. Jig and fixture design is a complex activity that needs extensive information and deep understanding about design, manufacturing, assembly and inspection. With the development of manufacturing technology, more and more flexible manufacturing systems and computer numerical controlled machine centers are used in industry. This causes a strong demand in computer-aided fixture design to shorten manufacturing cycle time and reduce cost. This thesis presents an object-oriented concurrent engineering system using an integrated semantic feature-based approach for automated jig and fixture design. A user may interactively design or modify a part model using the design-by-feature technique to specify all engineering properties such as material, hardness, dimension, dimensioning, tolerancing and surface finishing. A process plan will be generated for the part and it includes process details such as the machining methods, machining parameters and machining sequence arrangement. For each machining setup, a feature-based workpiece is generated from the process plan. A set of fixtures for the machining setup will be constructed based on the workpiece model and the derived cutter path. The cutter path is translated to G-code for manufacturing. The feature-based concurrent engineering system covers most application domains in production, i.e., design domain, manufacturing domain, assembly domain and inspection domain. To represent various information involved, a hierarchical structure with semantic feature definition is proposed. Semantic feature is defined as a group of abstract data with attributes not necessarily inclusive of geometric information. As sub-classes of feature, design_feature, manufacturing_feature, assembly_feature and inspection_feature are constructed to represent information in corresponding domains. Five operators used in feature transformation, namely [italic]equality, [italic]grouping, [italic]comparison, [italic]reference and [italic]reasoning, are identified and their operations within the system framework are defined. These feature classes and operators contain the vocabulary of the semantic feature-based language for information description. The concept of feature transformation is introduced. Rules for representing feature transformation in the semantic feature-based language, as the grammar of the language, are defined. The information manipulations within and across different application domains are described by feature transformations. The applications in generative process planning and automated fixture design for prismatic and cylindrical workpiece are developed. The validity of the system is verified by both simulating the cutting path on a workstation and machining the actual part on a CNC machine.