Introduction to
Mobile Computing
Aleksandar Kovačević, renesto@gmail.com
Mina Mićanović, minica82@EUnet.yu
Veljko Milutinović, vm@etf.bg.ac.yu
Aleksandar Kovačević & Mina Mićanović
1
Wireless Mobile or Mobile
Wireless?
• Wireless communication systems
are type of communication system
• Dimensions of mobility:
The set of properties that distinguishes
the mobile computing system
from stationary computing system
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Dimensions of
Mobile Computing
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•
•
•
•
•
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Location awareness
Network connectivity quality of service (QOS)
Limited device capabilities
Limited power supply
Support for a wide variety of user interfaces
Platform proliferation
Active transactions
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Mobile Development Framewor
and Tools
Aleksandar Kovačević & Mina Mićanović
4
Mobile Development
Frameworks and Tools
• Fully Centralized
Frameworks and Tools
• N-Tier Client-Server
Frameworks and Tools
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Fully Centralized
Frameworks and Tools
• Have custom-designed clients
• Embedded in nature
• Designed to do only one thing
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Fully Centralized
Frameworks and Tools
Applies:
• QOS
• Limiter power supply
• Active transactions
• Location awareness
Do not apply:
• Platform proliferation
• Limited device capabilities
• Support for variety of user interfaces
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Examples
• Call centers
• Battlefield systems
• Grocery store
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N-Tier Client-Server
Framework and Tools
• N-Tier -Any Number of Tiers –
No Limits
• 3-Tier
– Client (User Agent)
– Application Server
– Database
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Basic problems
• Code portability
• Mobility
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Needs
• Layer of Software
• Performance
and system requirements
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Selection of the
Frameworks and Tools
• Thin-Client Wireless Client-Server
• Thick-Client Wireless Client-Server
• Stand-alone Applications
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Thin-Client Wireless
Client-Server
• Browser that loads markup code
(Web-model)
• No concern about environment
• Server-side structure
• Example: WAP with his WML
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Thick-Client Wireless
Client-Server
• Client application-custom application
• Using the client
as a means of storing data
for the offline business logic performs
• Does not need to be centralized
• Having thick clients is more difficult
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Difficulties???
• Restricted resources
• Deployment and provision problem
– Operating system or virtual machine
– Programming environment
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Examples
• Operating system
– Windows CE
– Symbian
• Virtual Machine
– J2ME
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Stand-alone Applications
• They do not need
networking components
• Needs of synchronization
with some external system
periodically
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Some products
Connectivity
Networked
Stand-alone
Wired
Platform
Wireless
WAP
Symbian
Mobile
Platforms
BREW
Java
.NET
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JAVA - features
•
•
•
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Object oriented language
Complete code mobility
Weak mobile agent ability
It is a platform
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J2ME
Addresses the needs of
two categories of devices:
– Personal, mobile,
connected information devices (CLDC)
– Shared, fixed,
connected information devices (CDC)
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CLDC/MIDP Features(1)
Providing:
• a virtual machine
for providing language features
• a security framework
for tasks such as downloading MIDlets
(J2ME CLDC/MIDP applications)
*MIDP - Mobile Information Device Profile
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CLDC/MIDP Features(2)
Providing:
• a reasonable amount of functionality
for input and output
• some internationalization capabilities
• a reasonable amount of
networking capabilities
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KVM
Does not provide:
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–
–
–
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Floating point arithmetic
Support for JNI
Thread grouping
Full-blown exception
Automatic garbage collection of
unused objects
– Weak references
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CLDC/MIDP features
• Providing a security framework
for tasks such as downloading MIDlets
(J2ME CLDC/MIDP applications)
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CLDC/MIDP features
• Providing
a reasonable amount of functionality
for input and output
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Internationalization
capabilities
• Provides I/O stream readers
that can handle
different character encoding schemes
Two ways of internationalization:
• Dynamic
• Static
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Profiles
• The areas addressed by profiles
are the following:
–
–
–
–
–
Download and installation of application
Life-cycle management of application
User interface feature
Database functionality
Event handling
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CLDC profiles
• MIDP
(Mobile Information Device Profile)
– Widely known and accepted
• Personal Digital Assistant Profile
(PDAP)
• etc.
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MIDP
Designed for devices with assumed
characteristics
• Small displays
(96x24,1:1 shaped pixels, depth 1bit)
• Min 128kB of nonvolatile memory
(for storing application itself)
• Wireless connection to the internet
• Min of 8kB of nonvolatile memory
(for use by the application)
• ITU-T phone keypad
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Overview of the CLDC and
MIDP Java APIs
• J2SE-like APIs –
inherited from the J2SE environment
– java.lang.*
– java.io.*
– java.util.*
• CLDC-specific APIs
– javax.microedition.io (connector class)
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Networking Capabilities
• J2SE assumes the availability
of a TCP/IP connection
• CLDC defines
a connection framework in its Java API
example – WAP-style connections (WDP/UDP)
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Review of MIDP APIs
• Timers
– java.util.Timer
– java.util.TimerTask
• Networking
– HTTP implementation
– javax.microedition.io.* holds
HttpConnection
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Review of MIDP APIs
• Storage
– javax.microedition.rms.*
(RMS-Record Management System)
– for storing and retrieving data
• User Interface
– javax.microedition.lcdui.*
user interface APIs to build interfaces for MIDlets
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Hello MIDP example
For a J2ME class to qualify as a MIDlet,
it has to do the following:
1. Extend the MIDlet class
2. Implement the following methods:
a) startApp()
b) pauseApp()
c) destroyApp(boolean b)
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Hello MIDP example
import javax.microedition.midlet.*;
import javax.microedition.lcdui.*;
public class HelloMIDP extends MIDlet implements
CommandListener {
public static final String HELLO = “Hello MIDP”;
private DIsplay mDIsplay;
private Command mExit;
public HelloMIDP() {
mDisplay = Display.getDIsplay(this);
mExit = new Command(“Exit”, Command.SCREEN, 1);
}
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Hello MIDP example
public void startApp() {
TextBox myMessage = new TextBox(HELLO, HELLO, 256,
0);
myMessage.addCommand(mExit);
myMessage.addCommand((CommandListener) this);
mDisplay.setCurrent(mDIsplay);
}
public void pauseApp() {}
public void commandAction(Command aCommand,
Displayable aDisplayHandle) {
if (aCommand == mExit) {
destroyApp(false);
}
}
public void destroyApp(boolean b) {
notifyDestroyed();
}
}
}
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Sun’s Development Kit
Offers following components:
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•
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•
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KToolbar (GUI)
Preverifier
Compiler
Emulators
Emulation of Performance
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Dimensions of Mobility by
CLDC and Profiles
• Location awareness
– no treatment
– javax.microedition.location
•
•
•
•
•
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Network QOS
Limited Device Capabilities
Limited Power Supply Management
Support for a Large Variety of User Interfaces
Platform proliferation
Active Transactions
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XML & J2ME
Types of parsers:
• Model Parsers
• Push Parsers
• Pull Parsers
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Using UML to Model J2ME
Applications
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•
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Class Diagrams
State Diagrams
Component Diagrams
Sequence Diagrams
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CDC
• Targeted at environments
where more than 512kB
(usually about 2MB) of memory
is available for the Java environment
• CDC Profiles
are built on top of the Foundation Profile
• CDC has his own virtual machine
(CVM-C Virtual Machine)
• CVM supports all of the features
that the J2SE VM does
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Java Card
• Smart cards – embedded processor or
electronic memory device
• Java Card API –
allows interoperability
between different card readers/writes
and cards regardless of the manufacturer
and Java Card API implementer
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Java Card
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Three Types of
Smart Cards
• IC (Integrated Circuit)
Memory Cards
• IC Microprocessor Cards
• Optical Memory Cards
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JINI
Java Intelligence Network Infrastructure
– a base technology for ad-hoc networking
Basic transaction that JINI provides:
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Lookup
Discovery
Events
Leasing
Joining
Transaction Management
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JINI Specification
• Most today’s implementations
are not designed for mobile devices
• There are some that offer
“mobilized JINI”
– PSINaptic
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Java-based Peer-to-Peer
Protocol
JXTA – peer-to-peer protocol
Implementation on J2ME
– Direct Implementation
(JXTA APIs - provided on J2ME device)
– Indirect Implementation
(JXTA through proxies)
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BREW
BREW
(Binary Run-time Environment for Wireless)
• It is built directly on hardware
• Software Development Kit (SDK)
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BREW SDK Overview
•
•
http://www.qualcomm.com/brew
– register as a developer
– download BREW SDK
– offered only as a integrate set of components with MS Visual
C++ 6.0
You get this applications
– BREW MIF Editor
– BREW Device Configurator
– BREW Emulator
– BREW Image Authoring Tool
– BREW ARM Compiler
– Image Converter
– BREW Resource Editor
– BREW Pure Voice Converter
– BREW AppLoader
– BREW Grinder
– BREW TestSig Generator and AppSigner
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Building and Deploying a
BREW Application
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Download the SDK and get started
Obtain a Verisign Class 3 certificate
Get a BREW phone
Register as a BREW developer
Obtain a Class ID for your application
Perform a unit test and send it to a testing lab
Perform a pricing and carrier evaluation
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Get a BREW
and Start
Obtain Class 3
Certificate from
Verisign
True BREW Test
Unit Test
Get a Class ID
Download SDK
No
Done
Phone
Develop
Yes
Pricing and Carrier
Evaluation
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Hello BREW
• AEEClsCreateInstance
– BREW Run-time environment
• HelloBREW_HandleEvent
– EventHandler
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Architectural Concerns
About BREW Application
• Everything in BREW is event driven
(tight coupling to the hardware platform)
• Two groups of APIs you can use:
– those provided by qualcomm
– those provided by third-party vendors
• BREW API is still developing in C
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Windows CE
Different flavors
of the Windows CE OS,
depending on
hardware platform.
• Pocket PC
• Windows CE .NET
• Pocket PC 2002
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Tools to build Applications
• Embedded Visual C++
– separate from Visual Studio
– Emulators and a debugger is provided
– exception handling, run-time debugging
• Embedded Visual Basic
– can be developed faster
– no ability to be tuned and optimized
for resource-starved mobile devices
• Smart Device Extensions for .NET
• Microsoft Mobile Internet Toolkit
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eMbedded Visual C++
Compilers available for:
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•
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•
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ARM
MIPS
Intel’s x86
PowerPC
Hitachi processors
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eMbedded Visual C++
Provides:
• a subset of the Win32 APIs
for building Windows CE applications
• a subset of the MFC
(Microsoft Foundation Classes) libraries
• a set of classes specific
to the Windows CE platform
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Things You Should keep in
mind
•
•
•
•
Graphics are expensive
Use events instead of polling when possible
Economize with your memory (saving power)
Provided functionality of getting the status
of the Power Consumption
– useful for testing application
– useful to change behavior of application
• Clean up memory resources
whenever you get WM_HIBERNATE event
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Databases on Windows CE
Three ways to store data:
• MS SQL Server Windows CE Edition
– most functionality
– takes the most resources
– offers only subset of its desktop/server version
• views
• stored procedure
•
CEDB
– small and simple database
– it’s not relational database
•
File System
– fewer resources
– increases the application
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Windows CE and
Web Services
• Importance of XML-based Web Service
• .NET has Web Service-based functionality
based on two key technologies:
– WSDL (Web Service Definition Language)
– SOAP (Simple Object Access Protocol)
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Microsoft Smart Phone
• Microsoft Smart Phone 2002,
Microsoft's attempt to enter
the mobile technology market
• It can host custom applications
written using smart phone SDK.
SDK is provided
as a plug-in for eVC
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WAP
•
•
WAP – Wireless Application Protocol
Installed on almost every mobile phone
Basics about WAP:
• WAP is intended for thin clients
– all logic calculated on the server
– simple display instructions in some markup language
are done by the client
•
•
•
WAP is built on its own lower level communication protocol
Typical deployment of WAP includes a proxy or a gateway
WAP is a complete framework for a mobile applications
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WAP Architecture
• It’s a client-server Architecture
• Implementation standards
– for client to interpret content
– communication mechanisms
between the clients and the servers
– additional required features in the server
(particulary proxy servers)
• Communication functionality
between clients and server:
– Handling of Telephony on the Device
– Push
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Basic Communication
Architecture in WAP
WAP Client
WAP Proxy /
Application
Gateway
Server
HTTP/
HTTPS
WSP,WTP,WTLS,WDP
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WAP UI
Developing WML pages
WML – Mark-up language rendered by the WAP micro browsers
Advantages over HTML
• WML tag is smaller
• WML is XML compliant
• WML is designed for small monochrome screens
– allows breaking a page into a deck of cards
– allows client-side navigation between the cards
•
WML has mark-up tags
that allow interacting with the telephony
Disadvantages
• Most content on Internet is in HTML
• Conversion of HTML to WML is not easy process
– WAP 2.0 fixes that using XHTML that is well-formed
and using XML techniques like XSLs to convert XHTML to WML
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WAP
Proxies and Gateways
• A server that supports
WAP and HTTP
• Difference
between the proxy and the gateway:
user can determine will he use proxy
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WAP Gateways (1)
Features of WAP Gateways:
• Security
– Handoff point between WTLS
(Wireless Transport Layer Security)
to external security mechanisms (SSL)
• Network Access
– Access point
– Controlled access by Network Provider
• Protocol Conversions
– Converting WSP (Wireless Session Protocol)
to HTTP
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WAP Gateways (2)
• Caching
– Extremely aggressive caching
– cache expire must be set manually
– reduces the pervasiveness of content
• Preparation of Content and Scripts
– Gateway encodes WML
into Compiled WML (WMLC)
– WMLScript must be compiled
before being sent to client
• Functionality offered through WAP 2.x
– offering model of connectivity that puts
increasingly less functionality into the proxy
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MMS
MMS - Multimedia Messaging Services
• WAP MMS is a standard
• Overview:
– Presentation
• handled through SMIL
(Synchronized Multimedia Integration Language)
– Addressing
• two addresses:
– address of the MMS Proxy-relay
– address of the recipient user and terminal
– Delivery is possible through variety of interfaces.
These include the following:
a. MMS proxy-relay
b. Standard email interface (supports any email protocol)
c. Legacy wireless messaging systems
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WAP Push
• Based on Push Access Protocol (PAP)
• Push operation
WAP push event do the following:
• The mobile device connects
and registers to Master Pull Proxy
• Application Server establishes a connection to PPG
through PAP protocol
• The content being pushed can be a multipart document
following the MIME format
• The user agent profile is accessed.
• The message is then sent to PPG
• The devices receives the message
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Security
• WAP does not have application
authorization
• Offers guaranteed authentication
of user devices
• Offers guaranteed integrity
of transactions
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Symbian EPOC
• Symbian OS 7.0 supports:
MMS, HTTP, SyncML, SMS,
Mobile IP, IrDA, and Bluetooth
• It has free SDK
(supported languages: C++ and Java)
• Designed more as a PDA OS
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Publishing Frameworks
• Presenting content in several different formats
• Matching the type of document
requested with the type of document available
(or one that may need to be generated at run time)
• Modularized infrastructure that separates
the various components of the framework,
the processing components, and the content
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Publishing Frameworks
Examples:
• Apache’s Cocoon
– best known publishing framework today
– written in Java, supports ASP, Java and XSL (and many other)
•
IBM’s Wireless Transcoding Publisher
They treat the user interface problems presented by the following:
• Proliferation of mobile devices
• Localized and Internationalized user interfaces
• Selection of segments of multichannel content
• Selection and composition of content based
on device information
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Cocoon
• Open-source – widely accepted
• Got his name from the movie
• Cocoon’s Architecture aim to separate:
–
–
–
–
content
style (the formatting of content)
logic (how content is generated or chosen)
management of content (creating content)
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Cocoon’s Architecture
Generators
Serializers
PDF
XML
VXML
Binary
WML
Java
XHTML
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Mićanović
Transformers
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Generators
• Take static/dynamic content
• Generate XML in the form of SAX events
There are series of generators:
• File generator
• Server pages generator
• JSP generator
• Request generator
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Transformers
• Xalan –
XSL transformation engine
• XSLs are not platform dependent
or language dependent
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Serializer
• Responsible for publishing
to the client through HTTP response
• FOPSerializer
(Converts HTML to PDF)
• SVG Serializer
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IBM Wireless Transcoding
Publisher
• Focusing on product,
IBM Wireless Everyplace Suite
• Integrated environment with
IBM’s Websphere Application Server
• Our focus is on pervasive
and mobile aspects of this suite
and comparison with Cocoon
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Overview of IBM
Everyplace Suite
Addresses issues like:
• wireless connectivity
• content management
for wireless clients
• wireless security
• provisioning and device management
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Comparison of the
WTP and Cocoon
• WTP offers better functionality
in converting HTML
to any other markup language than Cocoon
• WTP offers custom transformers
that convert variety of image formats
• WTP offers a set of WAP devices
that allow very simple publishing
of HTML and XML content
to WML-enabled devices
• Very rich set of tools for developers
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Other Tools
• Asynchronous Messaging Systems
• UML Tools
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XML for Mobile Computing
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XML and Mobile
Applications
• Mobile applications should understand
and be able to manipulate XML content
• Mobile applications use XML
to facilitate their implementations
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Key XML Technologies for
Mobile Computing
•
•
XHTML
VXML
– designed for voice user interfaces
– allows specification of a command-based voice dialog
through a markup language
•
•
•
•
•
•
•
WML
XForms
CCXML
XML Pipeline
WBXML
SSML
RDF
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CCXML
Call Control Extensible
Markup Language
– Application of XML
for managing voice calls
– It focuses on routing the calls
and connecting calls (in contrast to VXML)
– It is based on Java Telephony APIs (JTAPI)
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XML Pipeline
• It specifies how to process
various XML resources
It can be thought in two different contexts:
• It specifies the flow of processing instructions
that are applied to one or more given documents
residing on the host
• It specifies the flow of processing instructions
that are applied to a variety of XML documents,
residing at a variety of hosts
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Sample XML Pipeline
Document
<?xml version=“1.0”>
<pipeline xmlns=“http://www.w3.org/2002/02/xml-pipeline”
xml:base=“http://www.cienecs.com/Examples/XMLPipeline”>
<param name=“target” select=“’result’” />
<!– This section defines the processes and links them to their definitions (typically some hint to
the controller on where and how to start off the processes). We chose Java for our
examples, so the definition is in terms of Java classes. --!>
<processdef name=“selector” definition=“com.cienecs.mobile.http.get_content_selector” />
<processdef name =“selector_content”
definition=“com.cienecs.mobile.http.get_content_generator” />
<processdef name=“authenticator” definition=“com.cienecs.mobile.security.authenticator
($username) ($password)” />
<processdef name=“transformer” definition=“com.cienecs.mobile.transformer.xslt” />
<!– For our example, we chose a set of processes that select some content based on the user’s
request. SO, the first thing to do is to find the content that the user requested. --!>
<process id=“3” type=“selected_content” >
<input name=uti_param_1” label=“content_finder_param_1” />
<input name=“uri_param_2” label=“content_finder_param_2” />
<output name=“cresult” label=“generic_content_URI” />
</process>
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Sample XML Pipeline
Document
<!– For our example, we want to transform the content based on the device that the user is using.
SO, we need to fire off a process that finds out the user’s device type.. --!>
<process id=“1” type=“selector” >
<input name=“deviceId” label=“unique_device_id” />
<input name=“ccpp_header_string” label=“ccpp_header_string” />
<output name=“result” label=“device_type” />
</process>
<!– Now, based on the user’s device type and the selected content, we can find the right type of
transformer and transform the content properly. --!>
<process id=“2” type=“transformer” >
<input name=“device_type” label=“device_type” />
<input name=“generic_specific_URI” label=“generic_content_URI” />
<input name=“authenticated” label=“authenticated” />
<output name=“device_specific_content” label=“device_specific_content” />
</process>
</pipeline>
Aleksandar Kovačević & Mina Mićanović
90 / 95
XML Pipeline
Recognize type of processes:
• Constructive processes produce new information
• Augmenting processes add new types (definitions)
of information
• Inspection processes look
at the content of a document
• Extraction processes copy
a part of the document that they look into
• Packaging processes are distributed processes
that address the processing of distributed resources
Aleksandar Kovačević & Mina Mićanović
91 / 95
WBXML
• WAP Binary Extensible Markup Language
• Defines a way to represent XML
in 0’s and 1’s instead of text
• KXML (parse WBXML)
Aleksandar Kovačević & Mina Mićanović
92 / 95
SSML
• Synthetic Speech Markup Language
• It is used for the infrastructure
of the voice user interface
Aleksandar Kovačević & Mina Mićanović
93 / 95
RDF
• Resource Description Framework
• Created specifically:
– to allow discovery of various resources
– indexing them
– creation of resources
that are made up of other RDF resources
by simply nesting the RDF descriptions
• RDF is part of Semantic Web.
Aleksandar Kovačević & Mina Mićanović
94 / 95
Thank You
for Your Attention
Aleksandar Kovačević & Mina Mićanović
95