Personalized Pocket Directories for mobile Devices

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Personalized Pocket Directories for mobile Devices

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

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Mobile Devices
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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???

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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.

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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.

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Web directory browsing

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

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Search on the internet

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

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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

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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

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Web directories on Mobile Devices

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

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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.

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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.

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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.

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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.

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From Web directories to Local capsules

• These capsules are dynamic replicas and not
  static snaphshots of the servers directory.
• The directory capsule is generated by a mediator
  a software component that accesses the Web
  Directory/Internet, encapsules the rights amount
  of information

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From Web directories to Local directory capsules
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From Web directories to Local directory
capsules
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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.

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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)

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The directory Model.

• The search in Directory Model.
• User can submit queries
• to
• The entire category
• A particular category
• About
• Categories
• Documents
• Persons.

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The directory Model.

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

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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 n1, the set of Entities
• R Rij 1 i,jn is the set of directional
  relationships between Ei and Ej

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The directory Model.

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

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The directory Model.
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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.

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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.

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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.

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The subscription Model
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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?

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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.

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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.

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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.

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Maintaining a consistent and Fresh directory
capsule

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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

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Maintaining a consistent and Fresh directory
capsule

• Load and sync must to not occur concurrently.
• Special care if the Directory model allows item
  deletions

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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.

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Sample Application

• Lotus Discovery Server.

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Sample Application

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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???