Not much needs to be said to define the functional data model: Variables are functions whose definitions may be changed by assignment statements. Types are sets of values that act as membership constraints on the domains and ranges of functions. That's it.
Despite the almost ridiculous simplicity of its definition, the functional data model provides as much security and power of expression as any other data model. The same can be expected of a programming language based on this data model.
At this stage it cannot be stated with absolute certainty that such a language would be efficient or even implementable. However, there are many good techniques for implementing sets and functions mapping sets to sets. It therefore seems likely that an efficient programming language, based on the functional data model, can be designed and implemented.