Solving conditional and composite temporal constraints

One of the main challenges when designing constraint based systems in general and those involving temporal constraints in particular, is the ability to deal with conditional constraints and composite variables. Indeed, in this particular case the set of variables involved by the constraint problem to be solved is not known in advance. More precisely, while some variables (called initial variables) are available in the initial problem, others are added dynamically to the problem during the resolution process via activity constraints and composite variables. Activity constraints allow some variables to be activated (added to the problem) when activity conditions are true. Composite variables are variables whose values are the possible variables each composite variable can take. We propose a method based on constraint propagation for solving efficiently constraint problems involving numeric and symbolic temporal constraints, composite variables and activity constraints. We call these latter problems conditional and composite temporal constraint satisfaction problems (CCTCSPs). Experimental evaluation conducted on randomly generated CCTCSPs demonstrates the efficiency of our method to solve these problems especially when using the forward check strategy during the search.