XCSP3: An Integrated Format for Benchmarking Combinatorial Constrained
  Problems
  We propose a major revision of the format XCSP 2.1, called XCSP3, to build
integrated representations of combinatorial constrained problems. This new
format is able to deal with mono/multi optimization, many types of variables,
cost functions, reification, views, annotations, variable quantification,
distributed, probabilistic and qualitative reasoning. The new format is made
compact, highly readable, and rather easy to parse. Interestingly, it captures
the structure of the problem models, through the possibilities of declaring
arrays of variables, and identifying syntactic and semantic groups of
constraints. The number of constraints is kept under control by introducing a
limited set of basic constraint forms, and producing almost automatically some
of their variations through lifting, restriction, sliding, logical combination
and relaxation mechanisms. As a result, XCSP3 encompasses practically all
constraints that can be found in major constraint solvers developed by the CP
community. A website, which is developed conjointly with the format, contains
many models and series of instances. The user can make sophisticated queries
for selecting instances from very precise criteria. The objective of XCSP3 is
to ease the effort required to test and compare different algorithms by
providing a common test-bed of combinatorial constrained instances.
