A P2P Distributed Adaptive Directory Gennaro Cordasco , Vittorio Scarano and Cristiano Vitolo

1. A P2P Distributed Adaptive Directory Gennaro Cordasco, Vittorio Scarano and Cristiano Vitolo ISIS-Lab –Dipartimento di Informatica ed Applicazioni ”R.M. Capocelli” Università di Salerno, 84081, Baronissi (SA) – Italy Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

2. Summary • Motivation to our work • The Bookmark • Distributed Adaptive Directory • The architecture • Peer to Peer • Adaptivity and Cooperation • The user interface • Evaluation • Conclusion and Future Work Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

3. Motivation to our work • Collaborative navigation We were born alone… we will die alone… but in the meantime we live with continuous relationships with others’ opinions, judgment and suggestions. • Everybody navigates in isolation… • Absolutely different from the real life • Everybody can get the knowledge of the whole group “I know as much as the sum of what other people know” Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

4. Motivation to our work(2) • Adaptive Environment • Our daily actions are continuously dictated and influenced by others as well as, of course, our actions influence others’ choices • Our society relies on such background activities with continuous feedback that induce a sense of community that makes everybody conscious of everybody’s behavior • if we want to share our experience the standard WWW offers little support: bookmarking an URL and sending it is one of them Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

5. The Bookmarks • Bookmarks are, nowadays, an important aid to navigation since they represent an easy way to reduce the cognitive load of managing and typing URLs. • All the browsers have always provided, since the very beginning of the WWW, friendly ways of managing bookmarks. • But with limited functionality Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

6. The Bookmarks(2) • Limitation • a high percentage of users usually does not organize at all the bookmarks (or organize them poorly) • How can I find an Interesting bookmark? • The user must insert, delete and organize his bookmarks Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

7. Previous work • Opencola is a commercial system that allows to share bookmarks between any web user • The Architecture is Client/Server • The user can search a bookmark by keyword • Each user can provide feedback on the search results • Opencola does not use a single ontology for all the clients • Opencola allows to view the classification chosen by the “owners” of the bookmark so that a certain amount of suggestion on the categorization is provided Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

8. Previous work(2) • Widesource is a freeware system • Uses a base ontology where to categorize bookmarks • The users can add other folders to the lower levels of the tree • It forces the users to place all the bookmarks to be shared in a single folder (loosing information on personal categorization) • It is not integrated with the browser Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

9. Distributed Adaptive Directory (DAD) • DAD is a P2P system (in Java) that offers a distributed, cooperative and adaptive environment for bookmark sharing. • It offers an adaptive environment since it provides suggestions about the navigation based on • the bookmarks • the feedback implicitly provided by users • the structure of the Web. Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

10. DAD architecture • MOM (Multimedia Ontology Manager), realizes the graphical user interface that represents a typical DAD-peer and allow to use all the functionalities of our system • The middle layer, exploits the bottom level to obtain information about bookmarks and users, providing a collaborative and adaptive system to manage bookmarks (DAD) • A P2P overlay network named CHILD (CHord with Identification and Lonely Discovery). This solution is inherently scalable with the large number of users that are potentially interested in bookmark sharing Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

11. P2P systems • Peer-to-peer (P2P) is a type of network in which each workstation has equivalent capabilities and responsibilities and each communication are potentially symmetric • Properties • decentralized control • adaptation • self-organization • Goals • sharing of content • distributed web servers, distributed media repository • sharing of storage • distributed file system, distributed search engine • sharing of CPU time • parallel computing Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

12. Scalability and Distributed Hash Table (DHT) • Scalability has been recognized as the central challenge in designing P2P systems • To obtain a scalable system, several P2P systems introduced the Distributed Hash Table (DHT) schemes: • object and nodes are associated with a key • each node in the system • is responsible for storing a certain portion of the key space • uses a routing scheme to forward the request for an object not belonging to its key space to appropriate next-hop node • A distributed hash table (DHT) is used to store information on how to locate bookmarks Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

13. CHILD • Our DHT is realized by using the Chord protocol, developed at MIT • It allows to locate information about each category (and bookmarks therein memorized) given its key. • Additional features added in our implementation of Chord: • A distributed P2P identification mechanism • A bootstrap mechanism based on a cache • Save and Reload capabilities Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

14. Bookmark organization • Our system allows users to create their own organization (even none, if that is the choice) for local bookmarks but share them (or importing them) with a fixed ontology • We use the (first 4 levels) of the ontology by Open Directory Project DMOZ (http://www.dmoz.org) • Specialized version of the ontology can be used for specialized groups Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

15. Bookmark storing • Bookmarks are stored in the DHT that is acting like a distributed filesystem: • when a user places a bookmark in the ontology (i.e., makes it shared with the system) his/her peer is in charge of storing the bookmark for the whole system • when a user needs to open a category in the ontology (an operation called expansion) his/her peer needs to know all the peers that are storing bookmarks for the category (called interest group) Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

16. Adaptivity • Kleinberg (1998) • When an author chooses to add a link from his page toward another page.. • he is inferring authority, importance, relevance, relationships,… • Kleinberg algorithm • Assign a score to nodes of a graph (i.e. HTML pages) based on the edge among them (i.e. links among HTML pages) • good authorities (nodes recognized as a good source of information) • good hubs (nodes recognized as containing good pointers to useful information) Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

17. Adaptivity(2) • Our system utilizes user bookmarks as well as user feedback and the underlying structure of the web to suggest and improve the navigation on the Web of all the users bookmark link • We extended Kleinberg algorithm by adding users to the set of nodes (i.e., bookmarks) therefore modelling also the interactions between users and bookmarks user Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

18. Scores • Each bookmark in our system has four scores: • Authority and Hub weight (Kleinberg algorithm) • Owners’ scores: the scores of the user that published the bookmark • Occurrences: the number of users that keeps locally the bookmarks Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

19. MOM Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

20. Bookmarks in DAD Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

21. Bookmarks properties Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

22. Bookmarks properties(2) • Our system is particularly well integrated with MS Internet Explorer Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

23. Evaluation • Two round of tests : • 12 participants with the base ontology • 21 participants with an ad hoc category • Two weeks for round • Qualitative analysis: • First round: users did not found particularly interesting the bookmarks of other users they appreciated much more the bookmarks suggested by the system • Second round: the participants appreciated the bookmarks inserted by other participants as well as the bookmarks suggested by the system The ontology used was too large more integration and sharing Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

24. Conclusions and Future Work • We showed • a pure P2P application (therefore inherently scalable) for managing communities of users that want to share the resources that they found • an adaptive mechanism • a highly tunable ranking mechanism • Future work • support bookmarks placed simultaneously in multiple folders • use the Kleinberg model (as modified by us) in determining subgroups and similarities among users • add backup capabilities by adding a certain degree of redundancy therefore improving the reliability of the whole application Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004

25. Thanks for your attention! • DAD is freely available under the GNU Public Licence at the project home page http://isis.dia.unisa.it/projects/DAD Adaptive Hypermedia 2004, Eindhoven, The Netherlands, August 24-26, 2004