Software for numerical solution of partial differential equations requires accessing, manipulating, and often modifying information about the geometry of the computational domain, the mesh used for the simulation, and discrete data stored on that mesh. Typically, applications programmers would prefer to avoid the difficulty and complexity of creating their own modules for tasks like interacting with multiple geometric modelers, mesh adaptation, and optimization algorithms, rightly preferring instead to focus on the problem physics and on studying the physical results that the code produces. Ideally, these modules would be provided by experts in CAD modeling, meshing, and optimization, and written so that they can use the application?s data regardless of the data structures used by the application. This paper describes a language- and data-structure-independent interface supporting query and modification of mesh data conforming to a general abstract data model.