This paper describes a novel approach for integrated assembly modelling and planning. The main objective is to make assembly information accessible and exploitable by data management systems and computer-aided X tools in order to support product architects and designers. Product information and knowledge as well as the related assembly sequence require a logical foundation in order to be managed consistently and processed proactively. In this context, product relationships are considered and described in the part-whole theory supported by mereology and its extension, mereotopology. Firstly, past and current research work are presented on concurrent product design and assembly sequence planning approaches; existing assembly relational models; and spatio-temporal mereotopology. A background of previous research work is also included in order to highlight the current research problem. Then, a mathematical description approach of product relationships based on mereotopology and temporal relationships is introduced. Finally, an ontological implementation of the proposed description using OWL DL and SWRL is presented and illustrated in a case study describing a mechanical assembly, enabling hence, reuse and collaborative exploitation of the assembly knowledge in the different product lifecycle phases. (C) 2012 Elsevier Ltd. All rights reserved.