Weighted Grammar Tools: The GRM Library. We describe the algorithmic and software design principles of a general grammar library designed for use in spoken-dialogue systems, speech synthesis, and other speech processing applications. The library is a set of general-purpose software tools for constructing and modifying weighted finite-state acceptors and transducers representing grammars.par The tools can be used in particular to compile weighted context-dependent rewrite rules into weighted finite-state transducers, read and compile, when possible, weighted context-free grammars into weighted automata, and dynamically modify the compiled grammar automata. The dynamic modifications allowed include: grammar switching, dynamic modification of rules, dynamic activation or non-activation of rules, and the use of dynamic lists. Access to these features is essential in spoken-dialogue applications.