Formal Aspects of Component Software

The International Symposium on Formal Aspects of Component Software (FACS) was inaugurated two decades ago in response to the major software development paradigm shift from structured development and object-oriented development to component-based software development (CBSD) and service-oriented architecture (SOA). FACS is dedicated to fostering a deeper understanding of the distinctive aspects, promoting research, education, technological advancement, and the practical application of CBSD technology. On the 20th anniversary of FACS, it is appropriate to briefly recall its background and history, thereby highlighting its contributions to the community. Taking this opportunity, we focus on the discussion to elucidate the important aspects of component software that require to be and have been considered in formal theories. Leveraging the refinement of component and object-oriented systems (rCOS) as a framework, we provide an overview of these formal theories and discuss their relationships. We intend to express a vision that different theories and methods are required for different aspects in a CBSD process, and also different formal theories are required even for a particular aspect. However, ensuring their consistent application remains a major challenge and this is a main barrier to the effective industry adoption of CBSD. Furthermore, we delineate emerging challenges and prospects associated with integrating formal methods for modelling and design human-cyber-physical systems (HCPS) - hybrid integration encompassing cyber systems, physical systems, and the mixed human and machine intelligence.