To facilitate designing and maintaining collections of business process models and corresponding implementation documents, it is of pivotal relevance to identify commonalities that a set of process types share. They allow for reusing parts of process models and are a prerequisite of efficient and consistent modifications. Discovering or constructing commonalities requires abstraction. With respect to model integrity, there is need for precisely specified abstraction concepts that enable convenient and secure adaptations to particular requirements. Against the background of various alternative approaches to foster abstraction in process modelling, this report is mainly aimed at investigating chances and specific challenges that relate to the conception of generalisation/specialisation for process types. For this purpose, a preliminary conception of process specialisation is proposed that is based on specialisation of static artefacts. A subsequent overview of existing approaches to specify a concept of process specialisation shows that none of these is satisfactory. Moreover, it will be shown that a conception of process specialisation that corresponds to specialisation of static artefacts is not possible. Finally, an outline of a relaxed conception of specialisation and the use of local meta process types are proposed as a possible loophole.