An ObjectBased Architecture For WAPCompliant Application

1
An Object-Based Architecture ForWAP-Compliant
Application

• ??Mario Cannataro Domenico Pascuzzi
• ??IEEE (JNL) / 2000
• ??? csshu
• ??2000/11/26

2
Outline

• Abstract
• Introduction
• An architecture to deploy portable WAP-compliant
  application
• Future Work

3
Abstract

• WAP suite have been developed, it lacks a
  complete general architecture integrating
  software components of both the Internet and
  wireless contexts in a transparent way.
• Presents a general architecture framework to
  develop and deploy portable application and
  services.

4
Introduction

• Constrains of the wireless networks-Low
  bandwidth-High latency-Unsteady
  connection-High Transmission Bit Error
  Rate-Low predictable services availability

5
Introduction(CONT.)

• Constrains of the wireless terminals-Small, low
  resolution display and limited user-input
  facilities-Limited computational
  resources-Many kinds of terminals

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Basic Component Of The WAP Framework

• µ browser
• Hosted by the mobile terminal.
• WAP gateway
• Allow the interworking operation between the
  wireless network and others kinds of data
  networks.
• A layered stack of protocols
• Specific designed for wireless environments.

7
The Development Of WAP-compliant Application

• Classical approach in developing WAP-compliant
  Application comprises the following choices
• Localisation of the application
• Content format(static or dynamic)

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Localisation

• A WAP application may be localised either on
• The WAP gateway
• WAP gateway acts as a server
• Realized the encode/decode function
• Host the static and dynamic WML content
• The Application Server
• WAP Gateway behaves as HTTP Proxy
• Apart from the encode/decode function, WAP
  Gateway realizes protocol conversion
• The application content can be coded in HTML or
  WML

9
Content Format
10
An Architecture To Deploy Portable WAP Application

• The four layers(figure 1)
• User Layer
• A mobile terminal with a WML µ-browser
• Network Layer
• Represented by the WAP gateway which act as a
  HTTP client
• Application Layer
• Composed by the Application Server implementing
  the business logic
• Data Layer
• Composed by the DBMS server and the hosted
  database

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An Architecture To Deploy Portable WAP
Application(2)
Figure 1. Architecture integrating WAP and WWW
12
An Architecture To Deploy Portable WAP
Application(3)
Table 1. The Communication Interface between
adjacent layer
13
An Architecture To Deploy Portable WAP
Application(4)

• In author design, the WAP gateway operates as
  proxy whereas the Application Server is executed
  on a different host have following advantages
• To separate the WAP-based connectivity operations
  by application implementation
• To implement the application Server using open
  standard object-based technologiesex Enterprise
  JavaBeans
• To provide an open and portable solution based on
  the use of standard APIs

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An Architecture To Deploy Portable WAP
Application(5)

• The Application Server is comprised the following
  layers
• Servlets
• Manage the HTTP communication with the WAP
  gateway
• Care of the dynamic WML/HTML code generation
• Session Beans
• Manage the maintaining of the application state

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An Architecture To Deploy Portable WAP
Application(6)

• Entity Beans
• Encapsulate the data source and offer an
  object-oriented interface to the data model
• This layer access data via JDBC
• The Application layer (Figure 2.)

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An Architecture To Deploy Portable WAP
Application(7)
Web Container
EJB Container
J D B C
Seeion Beans
Servlets
WML HTML Static Contents
Entity Beans
WML/HTML generation
Session management Data access
EJB low level services(HTTP,..)
Figure 2. The Application Layer
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Object-based Approach

• In this architecture the development of a WAP
  application comprises the following steps
• Data model definition
• Mapping of the data model using entity beans
• Discovery and definition of the business rules
• Mapping the business rules using session beans
• Definition of the servlets for dynamic(WML/HTML)
  code generation
• Component compilation
• Application Deployment in the Application server

18
Maintaining The State Of Wireless Application
Against Terminal Disconnections

• Static Session Identifier(SSI)
• It is used to identify a client and its current
  session
• SSI has the following features
• Uniqueness
• Temporal invariance
• Temporal validity
• Username is used as SSI in the proposed model

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Maintaining The State Of Wireless Application
Against Terminal Disconnections(CONT.)

• The proposed model consists of the following
  components
• An auxiliary database
• Used to store information about sessions and
  state of the application
• A Session Manager(SM) process
• Used to manage sessions and disconnections

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Auxiliary Database

• Comprised the Session table and State table
• Session table
• Keep trace of user sessions
• Contain the following attribute
• User username chosen by the user
• Date the date of creation/last access of the
  session
• URL storing the last URL invoked by client

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Auxiliary Database(CONT.)

• State table
• Store state variables, related to a specific user
  session
• ltparameter, valuegt
• The removal of a session causes the cascading
  eliminating of all the state information related
  to it

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Session Manager Process

• Independent of the application
• Offers a sets of session/state management
  services accessible by APIs or class method
• Session Manager primitives
• Table 2

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Session Manager Process(CONT.)
Table 2 Session manager primitives
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Session Manager Process(CONT.)

• Session Manager is involved
• During a connection(normal mode)
• After a client disconnection (recovery mode)
• SM manages session lifecycle which is based on
  the use of two timers (Timer1, Timer2) with
  associated timeout (Timeout1, Timerout2) see
  figure 3

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Session Manager Process(CONT.)
Close
NEW
Operation
Destroy
ACTIVE
Reconnection ! Resume
Reconnection Resume
Timeout1
Suspend
Recovery
Destroy
Timeout2
SUSPENDED
REMOVED
Destroy
Figure 3. Session state transition diagram
26
Implementation

• A system prototype for sales force automation has
  been implementation.
• Client
• Nokia 7110, Nokia WAP Toolkit
• Network Layer
• Nokia WAP Gateway
• Application Layer
• Java 2 Platform Enterprise Edition
• Data Layer
• SQLServer, Oracle DBMS

27
Future Work

• To complete implementation of the Session
  Manager
• Development of rewriting techniques to simplify
  the use of its functions

28
References

• The demand for Mobile value-Added Service -----
  Nokia White Paper
• Wireless Application Protocol Architecture
  Specification WAP Forum.
• Wireless Application Environment Specification
• Thomas Enderes, Design and Implementation of a
  Multiplexing Framework for the Wireless
  Application Protocol, Tech. Rep., University of
  Karlsruhe-Institute for Communication
  Engineering, May 27, 1999
• Kyriacos Sabatakais, Marcel Zumbhl, Steffen
  Krotsch, Mobile eCommerce
• Juha Leppanen, Timo Laakko, Markuu Kylanpaa,
  Prototype development for the WAP application,
  VTT Information Technology, Finland