Technical Reports (CIS)

Document Type

Technical Report

Subject Area

CPS Formal Methods

Date of this Version

May 2001


University of Pennsylvania Department of Computer and Information Science Technical Report No. MS-CIS-01-29.


Memory coherence is a commonly accepted correctness criterion for distributed shared-memory computing platforms. Coherence is formulated assuming a static architecture in which all processors can communicate with one another. In this paper, we argue that the classical notion is not appropriate for ad-hoc networks consisting of mobile devices with constantly changing communication topology. We introduce and formalize a new correctness criterion, called group coherence, as a suitable abstract specification for shared-memory computing architectures over ad-hoc networks. We show that two existing systems, the Coda file system and Lampson’s global naming scheme, satisfy our definition. Finally, we propose a timestamp-based extension of the popular Snoopy cache coherence protocol for caching in ad-hoc networks, and show it to be group coherent.



Date Posted: 31 October 2006