Behavioural equivalences for dynamic Web data

Peer-to-peer systems provide a simple and effective platform for data integration on the Internet, exchanging dynamic documents using Web services. Dynamic documents contain both data and references to external sources in the form of links, calls to Web services, or coordination scripts. XML standards and industrial platforms for Web services provide a technological basis for building such systems. Process algebras provide a formal framework for studying and understanding their formal properties. We have previously introduced Xdπ , a calculus for reasoning about dynamic Web data. It consists of locations, containing dynamic documents and π -like processes which communicate with each other, query and update these documents, and migrate to other peers to continue execution. Here, we study network equivalences for Xdπ and Core Xdπ , a reformulation of Xdπ which embeds the location structure in the processes. Using Core Xdπ , we study a process equivalence stipulating that two processes are equal if they have the same behaviour in equivalent networks. We also explore domain bisimilarity, which implies process equivalence and is easier to use in proofs. Our definition adapts a technique for reasoning about higher-order π -processes. In addition, it is sensitive to the set of locations present in the network, an approach we have not seen before. We use our process equivalence to study communication patterns used by servers in distributed query systems, and propose a new pattern involving mobile code. © 2007 Elsevier Inc. All rights reserved.

[1]  R. Bone Discovery , 1938, Nature.

[2]  Arnaud Sahuguet,et al.  Distributed Query Optimization : Can Mobile Agents Help ? , 2000 .

[3]  Julian Rathke,et al.  safeDpi: a language for controlling mobile code , 2005, Acta Informatica.

[4]  Davide Sangiorgi,et al.  A Theory of Bisimulation for the pi-Calculus , 1993, CONCUR.

[5]  Sergio Maffeis,et al.  On the Expressive Power of Polyadic Synchronisation in pi-calculus , 2002, EXPRESS.

[6]  Mario Tokoro,et al.  On Asynchronous Communication Semantics , 1991, Object-Based Concurrent Computing.

[7]  Robin Milner,et al.  A Calculus of Mobile Processes, II , 1992, Inf. Comput..

[8]  Peter Sewell,et al.  Nomadic pict: correct communication infrastructure for mobile computation , 2001, POPL '01.

[9]  Davide Sangiorgi,et al.  Behavioral equivalence in the polymorphic pi-calculus , 2000, JACM.

[10]  Andrew D. Gordon,et al.  A Type Discipline for Authorization Policies , 2005, ESOP.

[11]  Ioana Manolescu,et al.  Active XML: A Data-Centric Perspective on Web Services , 2004, Web Dynamics.

[12]  Davide Sangiorgi,et al.  The Pi-Calculus - a theory of mobile processes , 2001 .

[13]  Martín Abadi,et al.  A calculus for cryptographic protocols: the spi calculus , 1997, CCS '97.

[14]  Julian Rathke,et al.  Contextual equivalence for higher-order pi-calculus revisited , 2005, Log. Methods Comput. Sci..

[15]  Simon L. Peyton Jones,et al.  Template meta-programming for Haskell , 2002, Haskell '02.

[16]  George C. Necula,et al.  Safe, Untrusted Agents Using Proof-Carrying Code , 1998, Mobile Agents and Security.

[17]  Julian Rathke,et al.  Towards a behavioural theory of access and mobility control in distributed systems , 2004, Theor. Comput. Sci..

[18]  Peter Sewell,et al.  Iota: A concurrent XML scripting language with applications to Home Area Networking , 2003 .

[19]  Benjamin C. Pierce,et al.  XDuce: A statically typed XML processing language , 2003, TOIT.

[20]  James Riely,et al.  Resource Access Control in Systems of Mobile Agents , 2002, HLCL.

[21]  Alberto Mendelzon Foundations of Semistructured Data , 2001 .

[22]  Arnaud Sahuguet,et al.  Resource Sharing Through Query Process Migration , 2001 .

[23]  Cosimo Laneve,et al.  PiDuce: A Process Calculus with Native XML Datatypes , 2005, EPEW/WS-FM.

[24]  Nobuko Yoshida,et al.  On Reduction-Based Process Semantics , 1995, Theor. Comput. Sci..

[25]  CeriStefano,et al.  Comparative analysis of five XML query languages , 2000 .

[26]  Dan Suciu,et al.  Data on the Web: From Relations to Semistructured Data and XML , 1999 .

[27]  Robin Milner,et al.  Communicating and mobile systems - the Pi-calculus , 1999 .

[28]  Stefano Ceri,et al.  Comparative analysis of five XML query languages , 1999, SGMD.

[29]  Daniele Varacca,et al.  Semantic subtyping for the /spl pi/-calculus , 2005, 20th Annual IEEE Symposium on Logic in Computer Science (LICS' 05).

[30]  Davide Sangiorgi,et al.  Communicating and Mobile Systems: the π-calculus, , 2000 .

[31]  Davide Sangiorgi,et al.  Techniques of \ weak bisimulation up to " , 1992 .

[32]  Davide Sangiorgi,et al.  Expressing mobility in process algebras : first-order and higher-order paradigms , 1993 .

[33]  Andrew D. Gordon,et al.  Validating a Web service security abstraction by typing , 2002, XML Security.

[34]  Lucia Acciai,et al.  XPi: A Typed Process Calculus for XML Messaging , 2005, FMOODS.

[35]  Philippa Gardner,et al.  Modelling dynamic web data , 2003, Theor. Comput. Sci..

[36]  Steven J. DeRose,et al.  XML Path Language (XPath) Version 1.0 , 1999 .

[37]  Luca Cardelli,et al.  A Query Language Based on the Ambient Logic , 2001, SEBD.

[38]  Arnaud Sahuguet,et al.  Ubql: a distributed query language to program distributed query systems , 2002 .

[39]  Ioana Manolescu,et al.  Dynamic XML documents with distribution and replication , 2003, SIGMOD '03.

[40]  Andrew M. Pitts,et al.  A New Approach to Abstract Syntax with Variable Binding , 2002, Formal Aspects of Computing.

[41]  Murdoch J. Gabbay The π-Calculus in FM , 2003 .

[42]  Sergio Maffeis,et al.  Dynamic Web data : a process algebraic approach , 2006 .

[43]  James Riely,et al.  Resource Access Control in Systems of Mobile Agents , 2002, Inf. Comput..

[44]  Alfons Kemper,et al.  ObjectGlobe: Ubiquitous query processing on the Internet , 2001, The VLDB Journal.

[45]  Alfons Kemper,et al.  Hyperqueries: Dynamic Distributed Query Processing on the Internet , 2001, VLDB.

[46]  Arnaud Sahuguet,et al.  ubQL, a Language for Programming Distributed Query Systems , 2001, WebDB.

[47]  Robin Milner,et al.  Communication and concurrency , 1989, PHI Series in computer science.

[48]  Mario Tokoro,et al.  An Object Calculus for Asynchronous Communication , 1991, ECOOP.