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

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

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


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”


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


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


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


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


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


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.


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

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

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

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

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

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)

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)

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

We extended Kleinberg algorithm by adding users to the set of nodes (i.e., bookmarks) therefore modelling also the interactions between users and bookmarks

linkbookmar

k

user

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


MOM


Bookmarks in DAD


Bookmarks properties


Bookmarks properties(2)


Our system is particularly well integrated with MS Internet Explorer

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

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

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

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