This thesis work is based on the previous researches in design automation at Sandvik Coromant. The concept of product family description (PFD) has been introduced to the company to improve documentation of knowledge in engineering design process. Current documentation at the company for engineering design covers mostly the design definition part of the knowledge. PFD is constituted by design definition and completed by design rationale. This kind of documentation improves reusing, revising and expanding the knowledge at the company. On the other side, PFD is an input for design programming and a good engineering design description for a product provides more efficiency in design programming. The project is started by a survey for several principles and applications for knowledge modelling. Product variant master (PVM) and Semantic MediaWiki are selected by the results of the survey. To show the concept of PVM, modelling of a test product is done in product model manager (PMM) software. The main part of the project is setting up product family description (PFD) by capturing design rationale for the test product, implementing in Semantic MediaWiki. Since the design rationale is not documented, it was recorded during several meetings with the designer of the test product. The description is completed by including the argumentations about the rules, figures, dimensions and etc. Also in the project has been tried to improve and revise the description to make it more simple and efficient. Another objective of the project is to show Semantic MediaWiki as a candidate application for modelling knowledge at the company. In this step the applicability and functionality of both PFD and Semantic MediaWiki is seen. In the next stage the project findings and company documentation are evaluated. In this step has been tried to show the pros and cons of the project. The emphasis of the evaluation is on PFD and the alternative application. In the end a conclusion of the whole methods and findings of the project comes with discussion with people who were involved in this work.