Introducing esra, a Relational Language

Current-generation constraint programming languages are considered by many, especially in industry, to be too low-level, di- cult, and large. We argue that solver-independent, high-level relational constraint modelling leads to a simpler and smaller language, to more concise, intuitive, and analysable models, as well as to more ecient and eective model formulation, maintenance, reformulation, and veri- cation, and all this without sacri cing the possibility of ecient solving, so that even lazy or less competent modellers can be well assisted