The first part of the paper develops a novel, sortally-based approach to the problem of aspectual composition. The account is argued to be superior on both empirical and computational grounds to previous semantic approaches relying on referential homogeneity tests. While the account is restricted to manner-of-motion verbs, it does cover their interaction with mass terms, amount phrases, locative PPs, and distance, frequency, and temporal modifiers. The second part of the paper describes an implemented system based on the theoretical treatment which determines whether a specified sequence of events is or is not possible under varying situationally supplied constraints, given certain restrictive and simplifying assumptions. Briefly, the system extracts a set of constraint equations from the derived logical forms and solves them according to a best-value metric. Three particular limitations of the system and possible ways of addressing them are discussed in the conclusion.