This project combines the idea of a value oriented XML Store with a peer-to-peer distributed file system, based on the Chord protocol.
The distributed file system is based on Chord, a routing and location protocol developed at MIT, and provides a distributed hash table for storage of data. The Chord protocol is highly scalable as it looks up data in time logarithmic in the number of servers and requires only logarithmic space for routing information at each node. For more information see the Chord Project.
The concept of a value-oriented XML Store is part of plan-x, a software platform for value-oriented programming supporting transparency of distibution and mobility of data and applications. The term value-oriented denotes a style of programming where all data are considered immutable. When storing XML documents we employ a storage strategy, splitting XML documents up according to their inherent tree structure. Each subdocument is considered a value and stored separately in the distributed file system. This storage strategy offers many advantages over conventional text based technologies such as SAX and DOM, the most important being the possibility to obtain sharing of identical subdocuments.
A prototype of the distributed XML Store has been developed in java. The prototype has a simple and flexible value-oriented API for representing and manipulating XML documents. It takes advantage of sharing and uses the proposed storage strategy to handle manipulation of XML documents without having to read and parse the entire document into memory. The value-oriented approach makes it easier to maintain several document versions and simplifies usually complex problems in distributed systems, such as transaction handling, caching and replication management.
A distributed, value oriented XML Store. (Download as PDF).
Master Thesis by Tine Thorn, Mikkel Fennestad and Anders Baumann, Supervisor: Professor Peter Sestoft.
Gives a thorough introduction to the Chord protocol, value-oriented programming,
A peer-to-peer, value oriented XML Store (Download as PDF)
Paper by Tine Thorn, Mikkel Fennestad, Anders Baumann and Peter Sestoft.
A brief introducion to the concept of value-oriented programming, Chord etc.
A very experimental release of the XML Store prototype is available for download. It is in the early stages, so please exercise care and don't forget to report issues to us at xmlstore@it.edu.
The prototype has a number of limitations:
You can contact us at: xmlstore@it.edu