Topologically sorting VDM-SL definitions for Isabelle/HOL translation

There is an ecosystem of VDM libraries and extensions that includes a translation and proof environment for VDM in Isabelle. Translation works for a large subset of VDM-SL and further constructs are being added on demand. A key impediment for novice users is that Isabelle/HOL requires all definitions to be declared before they are used, where (mutually) recursive definitions must be defined in tandem. In this paper, we describe a solution to this problem, which will enable wider access to the translator plugin for novice users as well as real models.