In this paper we suggest measures for making the synthesis process more likely to succeed. As a first measure the synthesis task must be made intelligible by making the starting point, the way of reasoning, and criterion for conclusion of the synthesis clear. Secondly, the interactive synthesis process can be supported by a planning ingredient in the system as a way for the system and the user to communicate. The planning ingredient in a case study prototype system, IPSA, takes the role of both describing the performed synthesis steps as well as prescribing the future steps. The plan orders the inference steps in sequences of specific subtasks. There are four types of subtasks, three of which the system can perform without help and the four...