Enriching P2P with the semantic web

1. Enriching P2P with the semantic web D1.1 Overview of existing systems

2. Structure of talk • Refresh the definition • Three models • Three metaphors (orthagonal on models) • P2P Characteristics • Other things to think about • Protocols • The systems

3. P2P: definition • peer-to-peer computing is the sharing of computer resources and services by direct exchange between systems. • Resources and services include the exchange of information, processing cycles, cache storage, and disk storage for files

4. (1)Broker mediated model • Users register their content with a broker for sharing; use broker to find files to copy

5. (2)P2P sharing model • Does not require a centralized broker

6. (3)Resource sharing model • Data is processed by clients and returned to the master (SETI, Google?) (note that sending data is not always needed)

7. (1)Remote Procedure Calls • ‘Classical view’ • Peers invoking methods of other peers • API’s instead of Protocols • RMI, CORBA and more recently SOAP and JXTA XML (human readable)

8. (1)Peers as web services • Convergent themes, protocols, technologies, and applications with ‘classic P2P’ • Languages on top of XML/SOAP : • WSIL • WSMF • DAML-S • WSFL • …

9. (2)Peers as agents • ‘High level view’ • BDI model • Proactive, autonomous… • Agent communtication languages: FIPA, KIF, KQML • Speech act theory based on intents of the speaker (inform, query, error)

10. P2P characteristics:Interoperability • Protocols v.s. API’s (JXTA, FIPA v.s. Napster, SETI…) • Backward compatibility • Don’t overestimate the coolness of new features

11. P2P characteristics:Scalability (search) • Evolution in querying: Gnutella  Pastry  Poblano  Edamok/Edutella

12. P2P characteristics:Network efficiency • Reducing (other) redundant traffic • Reducing load per node • Solutions (Gnutella): • Content caching • Right query/advertisement balance • Efficient routing mechanisms

13. P2P characteristics:Authenticity • How do you know that nobody manipulated your data? • Hashing (Pastry, Chord, CAN, Tapestry) • Encryption (JXTA) • Majority vote (Larissa)

14. P2P characteristics:Anonymity Free Haven distinguised the following: • Author: A document’s author or creator cannot be identified • Publisher: The person who published the document tothe system cannot be identified (gnutella broadcast) • Reader: People who read or otherwise consume data cannot be identified • Server: Servers containing a document cannot be identified based on the document • Document: Servers do not know what documents they are storing • Query: A server cannot tell what document it is using to respond to a user’s query

15. P2P characteristics:Identification Currently peer systems developed their own DNS Advantage user based than location based Disadvantage lack of interoperability Thus needing standards like MS Passport…

16. P2P characteristics:Fault tolerance • Problems: Unreachability, partitions • Solutions • Groove: relay nodes that temporally store messages • Magi: queue messages at the source • Napster, Gnutella: Uncontrolled replications • Freenet, Publius: Controlled replications

17. P2P characteristics:Digital Rights Management • Consumers want: • Immediately deliverment • Friendly user interface • Good price perfomance ratio • Producers want: • Legal profitable system • Secure system • Cost effective Solutions: Languages to describe the rights of the users in XML: • XrML (eXtensible Right Markup Languange) • ODRL (Open Digital Rights Language

18. P2P +SW characteristics:Peer selection service • Use knowledge about peers and content for query selection • Examples: Poblano, Edamok, InfoQuilt, InfoSleuth, Edutella

19. P2P +SW characteristics:Variation of ontologies Different peers will use different, though overlapping ontologies. Alignment, mapping and visualization tools will have to cope with different ontologies, even though no alignments are explicitly specified. Examples: Edamok, Edutella?

20. P2P +SW characteristics:Lack of precision Ontologies will be produced from various user interactions, like classifications into folders or usage of meta-data. This can lead to imprecise and contradicting information between or in ontologies Examples: Edamok, Edutella?

21. P2P +SW characteristics: ontological drift one cannot expect any maintenance to happen on the ontologies Examples: None…yet.

22. Other things:Licencing and dependancy • Open source • Platform dependance (Windows) • Producer dependence (.NET)

23. Other things:Listen to the users • Don’t think… If we build it, they will come Therefore another characteristic in the compare matrix is the success rate of the described systems

24. Protocols: Gnutella

25. Protocols: Gnutella • File sharing protocol • Identifier are IP numbers • Broadcasting queries • When attaching, every peer responds with some information about itself • Own communication language • No security • Implementations: Limewire, Morpheus, Bearshare…

26. Protocols: JXTA Project

27. Protocols: JXTA Project • Protocols • Peer Discorvery Protocol (find advertisements of peers) • Peer Resolver Protocol (send and retrieve queries) • Peer Information Protocol (learn about peers’ status) • Peer Membership Protocol (obtain membership reqs) • Pipe Binding Protocol (bind pipe advertisements to pipe endpoint) • Endpoint Routing Protocol (find route between peers) • Unix alike security model, however users are free to implement their own • XML based messages, however YML is easy to implement • Peer monitoring • Platform independent • UUID (128-bit id to refer to an entity like a peer, an advertisement or a service)

28. Protocols: JXTA Project: examples on JXTA impl. • Aislandagent framework • AllhandsEvent Notification application • AngelopeerrendezvousA p2p based interactive software for intra enterprise communication • GnougatFully decentralised file caching • GnovellaSome experiments with JXTA and document storage in an enterprise • GoA Go Tournament based on the JXTA Protocols • HaluJXTA media distribution application • Instantp2pJXTA Demonstration GUI • JnushareInformation sharing application based on GISP • Juxtaprosea web / discussion content sharing application • jxta-httpdProvides a Set of service & tools provinding web publishing • MyjxtamyJXTA - JXTA Demonstration Application (aka InstantP2P)…

29. Protocols: FIPA Project • Combination of speech acts, predicate logic and public ontologies • Searching agents in the DF • AP: physical infrastructure in which agents can be deployed • Agent: The fundamental actor on the AP • DF: The yellow pager agent (combinations possible) • AMS: Supervisor of the platform • MTS: Message Transport Service is the default communication method

30. Protocols: FIPA Project

31. Protocols: Pastry • 128 bit ID (e.g. hash from IP address) • Hashlist of content moved close to ID • Implementations: • SCRIBEgroup communication/event notification system. • PASTarchival storage systems. • SQUIRRELa co-operative web cache.

32. Protocols: Pastry

33. Systems: to be continued… • Neurogrid • Poblano • JXTA • Groove • Magi • Hailstorm • Freenet • Edamok • Edutella • InfoQuilt • InfoSleuth • Jade

34. Systems: Poblano • On top of JXTA • Based on three components • Codat Confidence (keyword, codatID, flag for local or remote and confidence value) • Peer Confidence (keyword, peerID, confidence value) • Risk (peerID, integrity of codat, accesibility, performance)