Personalized Pocket Directories for mobile Devices
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Transcript of 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???