||True competitive advantage can only result from the ability to bring highly customized quality products to the market at lower cost and in less time. Many customers are demanding customization and rapid delivery of innovative products. Industries now realize that the best way to reduce life cycle costs is to evolve a more effective product development paradigm using the Internet and web-based technologies. Yet there remains a gap between these market demands and current product development paradigms. Assembly plays a very important role in manufacturing industries, given that joints on a structure are inevitable because of the limitations on component geometric configurations and material properties along with various engineering requirements. Appropriate joints should be determined by considering mechanical and mathematical implications and assembly/joining knowledge. Currently, the effects of joining are analyzed upon completion of assembly modeling. This sequential process is arduous and time-consuming and is eliminated with the tools developed in this work. The existing CAD systems require that a product developer possess all the design and analysis tools in-house making it impractical to employ all the needed and newest tools. Existing assembly design methodologies have limitations on capturing the non-geometric aspects of a designers intent and the physical effects of joining in an Internet-based product development environment. In this work, new assembly design (AsD) frameworks and assembly operation tools (AOT) are developed to integrate AsD, virtual analysis, and decision making for e-product design and realization. The AOT include the assembly design (AsD), assembly implication (AsI), and assembly advisory (AsA) engines. The AsD formalism, which is the base of the AsD engine, represents the assembly/joining relations symbolically for computer interpretation, and the automatically generated AsD model is used for inferring mathematical/physical implications, as well as lean AsD information exchange. A new virtual assembly analysis concept is introduced to transparently predict the various effects of joining and is implemented in a service-oriented architecture. The AsA engine employs hierarchical semantic net to support an AsD decision by capturing AsD information and assembly/manufacturing knowledge. The concepts and AOT are validated using a case study of realistic mechanical assemblies.