The requirement of unity of invention serves a regulatory function in the interest of an efficient procedure up to grant (T 110/82 and F‑V, 8). It would be unfair to regard as having unity of invention those applications which, because of their heterogeneous content, entail a far greater than average expense to process, especially in respect of search, since this expense must partly be borne by the fees levied for other applications. A further aspect is the requirement for ready comprehensibility of the application's subject-matter, which may be impaired by heterogeneous subject-matter.
On the other hand, the general purpose of dealing with interconnected substantive issues within a single procedure would not be achieved if provisions relating to unity of invention were applied too strictly. For this reason, interconnected matter should not be split up needlessly (see F‑V).