(Named after the British mAThemATician Bertrand Russell (1872-1970)). Wm. Leler. Rule-based specificATion language based on augmented term rewriting. Used to implement constraint languages. The user must explicitly specify the tree-search and the constraint propagATion. . ["Constraint Programming Languages - Their SpecificATion and GenerATion", W. Leler, A-W 1988, ISBN 0-201-06243-7].