Monday, May 5, 2014, at 16h30 in Celestijnenlaan 200A (auditorium 00.225)
Layout of a state-of-the-art grounder
by Joachim Jansen (PhD student DTAI)
Knowledge Representation requires expressive high-level languages in order to specify the problem domain. Current state-of-the-art declarative systems use a ground-and-solve approach in which the high-level representation is transformed into a low-level one, that is sent to a solver to calculate a solution. This transformation task is called "grounding". Grounding efficiently is difficult and intelligent techniques are needed to ensure a robust and fast grounding phase. IDP is such a state-of-the-art system based on a problem specification containing among others formulas and definitions.
In this presentation I will present a high-level overview of IDP's grounder and its workflow, describing what techniques are present and detailing their contribution to the grounding process. I will zoom in on two tasks: Lifted Propagation; the deriving of information before grounding and Bounded Grounding; using bounds on possible values to prevent unnecessary parts of the grounding. Using an example, I will introduce a new technique that derives more information from definitions than our existing implementation, which is an approximative measure that transforms definitions to formulas. Finally I sketch a new approach to ground definitions, as our current implementation can only be applied to efficiently ground formulas, and not definitions.