personalized pocket directories for mobile devices

Personalized Pocket Directories for mobile Devices

Doron Cohen – Miki Hersovici – Yael Petruschka – Yoelle Maarek – Aya Soffer – Dave Newbold

Mobile Devices

Mobile Devices (contd.)

Ability to access information anytime and anywhere.

Dramatic increase in the use and availibility of mobile devices.

Which avenir?– IDC: At the end of 2002: more wireless

subscribes than wired users! …– Is it right???

Web on mobile devices? Dream to reality…

Limiting factors:– Form factor

Limited screen. Input capabilities. Other?...

– Communication mode: Connection through networks with low bandwith High latency.

Web on Mobile Devices? From dream to reality

Other restrictions:– Limited storage.

Less an issue: possibility to add memory sticks.

– Limited CPU No real impact on the specific application, browsing.

Web directory browsing

Two common modes of information discovery on the internet (1994):– Search– Browse

Search on the internet

Finding narrowly defined information.– Google: http://www.google.co.il– Altavista: http://www.altavista.com

Browsing on the Internet

Good for presenting broad categories of information.– Yahoo: http://www.yahoo.com– Open Directory Project (ODP) :

http://www.dmoz.org– Looksmart: http://www.looksmart.com

Browsing on the Internet (contd.)

Is it popular?– Yes… Being bigger and bigger…

Open Directory: – 3 millions sites– More than 40.000 editors.– 500.000 categories.

Special purpose and regional directories– Environmental Organization Intranet– Lotus Discovery Server

Web directories on Mobile Devices

Fast and convenient browsing of directories. Minimal over-the-air communication

Web directories on Mobile Devices

Proposed solution:– Caching enough information on the device– Communicating with the server only for the last

stage. Minimal storage capabilities:

– PalmOS, PocketPC…– Nokia 9210, Motorola i85s, Palm Powered Phone

Regular connection to the internet.

Web directories on Mobile Devices

The approach:– “intermittent connection” communication model:

User synchronize its device via a cheap reliable and fast connection:

– Sync in Palm.– Other examples?...

And caches locally as much information as possible for working offline.

Web directories on Mobile Devices

Need to define a subscription model that adapts the specific nature of Web Directories– What is the “right” amount of information to be

isolated?– “Directory Capsule” The portion of directory to

transmit to the PDA to be seen offline.

Web directories on Mobile Devices

Four requirements:– An architecture that supports intermittently connected

devices.– A subscription model geared for Web directories and

targeted to PDA– A mechanism to ensure that the directory capsule is

consistent with the directory server– A fully featured pocket directory browser application for

defining, viewing, manipulating directory capsules on the PDA.

From Web directories to “Local capsules”

These capsules are “dynamic replicas” and not static snaphshots of the server’s directory.

The directory capsule is generated by a mediator: a software component that accesses the Web Directory/Internet, encapsules the rights amount of information

From Web directories to “Local directory capsules”

From Web directories to “Local directory capsules”

WorkloadInitiated by

Heavy

-Manually

- At some preschuled

time

Load

LightThe userSync

From Web directories to “Local directory capsules”

In a Palm context:– The mediator machine:

The desktop used to backup the device.

– The Synchronization process: HotSync process.

A bit formalism… The Directory Model

Web directories consist of a hierarchy of categories.

Each category may – contain:

Documents. Other categories.

– Be associated with one or more persons (Authorities)

The directory Model.

The search in Directory Model. User can submit queries

– to The entire category A particular category

– About: Categories Documents Persons.

The directory Model.

Search results can be viewed as “Virtual categories:– Categories that answer the query– Documents not in category– Persons.

The directory Model.

What are the relations between the different entities of the Directory Model.

The Directory Information (DI) can be defined as :– DI = (E,R)– E = {E1, E2, …, En} n=1, the set of Entities– R = {Rij; 1 =i,j=n} is the set of directional

relationships between Ei and Ej

The directory Model.

For example, in the Open Directory:– E1 – OD categories– E2 – Web pages – E3 – Persons– E4 – Query Results (Virtual Categories)

The directory Model.

E4 – Search Results

E1 – Category

E3 - Person

E2 - Site

E1 – Category

E4 – Query Results

E3 - Person

E2 – SiteRij

The Subscription Model

Mechanism for indicating the directory entities in which they are interested

The content of these entities will be extracted and stored in the directory capsule.

This content will be synchronized with the directory server.

The subscription model

Question: What is a “content of an entity”? The answer will have significant implications

in terms of – size of the local replica– Time it takes to refresh this replica.

The subscription model

We, therefore, define 2 granulaties of content for each data item:– Summaries : are stored for each entity included in

the capsule– Details : need only be stored for a subset of

these.

The subscription Model

Summaries of returned sites and categories

The query that produced these

resultsE4 Query results

Email, summaries of categories edited by

person, and bookmarks

Person Name, and profileE3 Person

The complete site page

Site title, description, and URLE2 Site

Summaries of editors, of contained sites, of

contained and direct parent categories

Category name and descriptionE1 Category

DetailsSummaries

The subscription Model

Another definition for categories:– Category Summary: Name, description, and

summaries of contained categories and of its parent category

– Category details: summaries of editors and of contained sites.

Which Differences? Which advantages?

Maintaining a Consistent and Fresh Directory Capsule

We need an – up to date– Consistent with the parent directory.

It is handled by the mediator component. Must be conducted as fast as possible.

Maintaining a Consistent and Fresh Directory Capsule

The capsule can be divided in:– Capsule definition: user subscription request– Capsule content: data loaded from the Web.

Maintaining a Consistent and Fresh Directory Capsule

Inconstitency can occur when:

– User induced inconstitency: The user added or deleted subscriptions

– Directory induced inconstitency: The directory has evolved since the last sync.

Maintaining a consistent and Fresh directory capsule

Maintaining a consistent and Fresh directory capsule

The both types of inconstitency are resolved by the Mediator– During Sync: A new definition is obtained from the

device. Unsubscribed items are deleted from the content.

– During load: The capsule content is updated from the directory:

Newly subscribed items are retrieved. Subscribed, modified items are updated Etc…

Maintaining a consistent and Fresh directory capsule

Load and sync must to not occur concurrently.

Special care if the Directory model allows item deletions…

Maintaining a consistent and Fresh directory capsule

Efficiency enhancement:– An additional mirror of the capsule content could

be stored on the desktop.– Why?

Computing “new” and “last updated” can be achieved during “Load”

Only “new” and “last updated” are download to the PDA.

Sample Application

Lotus Discovery Server.

Sample Application

Conclusion Remark

Model for browsing Web directories with minimal amount of storage capabilities

Based on the intermittent connection Does the PDA or mobile phones are the only

ones devices needing such a policy???