Departmental Papers (CIS)

Document Type

Journal Article

Subject Area

CPS Theory

Date of this Version

11-25-2008

Publication Title

Logical Methods in Computer Science

Volume

4

Issue

4

First Page

1

Last Page

44

DOI

10.2168/LMCS-4(4:11)2008

Abstract

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 expressively-complete. 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 (RSMs). The other logic, NWTL, is based on the notion of a summary path that uses both the linear and nesting structures. For NWTL we show that satisfiability is EXPTIME-complete, and that model-checking can be done in time polynomial in the size of the RSM model and exponential in the size of the NWTL formula (and is also 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 two-variable fragment of first-order.

Permission Statement

This work is under a Creative Commons Attribution-NoDerivatives (CC BY-ND) 2.0 license.

Keywords

Nested Word, Temporal Logic, First-Order Expressive Completeness, Three-Variable Property, Nested Word Automata, Model Checking

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Date Posted: 15 October 2009

This document has been peer reviewed.