First-Order and Temporal Logics for Nested Words

Nested words are a structured model of execution paths in procedural programs, reflecting their call and return nesting structure. Finite nested words also capture the structure of parse trees and other tree-structured data, such as XML. We provide new temporal logics for finite and infinite nested words, which are natural extensions of LTL, and prove that these logics are first-order expressivelycomplete. One of them is based on adding a ”within” modality, evaluating a formula on a subword, to a logic CaRet previously studied in the context of verifying properties of recursive state machines. The other logic is based on the notion of a summary path that combines the linear and nesting structures. For that logic, both model-checking and satisfiability are shown to be EXPTIME-complete. Finally, we prove that first-order logic over nested words has the three-variable property, and we present a temporal logic for nested words which is complete for the twovariable fragment of �...

• Type: Conference
• Year: 2007
• Where: LICS
• Authors: Rajeev Alur, Marcelo Arenas, Pablo Barceló, Kousha Etessami, Neil Immerman, Leonid Libkin
• Keywords: Computer Science, Infinite Nested Words, LICS 2007, Logic, Nested Words