IELM 511: Information System design
Introduction
Part 1. ISD for well structured data – relational and other DBMS
Info storage (modeling, normalization)
Info retrieval (Relational algebra, Calculus, SQL)
DB integrated API‟s
Part 2. ISD for systems with non-uniformly structured data
Basics of web-based IS (www, web2.0, …)
Markup‟s, HTML, XML
Design tools for Info Sys: UML
Part III: (subset of)
API‟s for mobile apps
Security, Cryptography
IS product lifecycles
Algorithm analysis, P, NP, NPC
Agenda
Need and applications of mobile apps
Problems in development of mobile apps
Case study: Google Android
Concluding remarks
Mobile computing: Needs and Applications
Location and guidance systems, e.g.
GPS and Map-based services
Logistics services, e.g.
FedEx/DHL delivery tracking/receiving systems
Ubiquitous computing, e.g.
Internet fridge, Home device controls, Building security systems
Mobile computing: Issues
Hardware:
Lower Bandwidth (wireless bandwidth is lower than wired)
Data transfer is slower (e.g. poor performance of iPhone GPS)
Limited battery power
Restricted to low power consumption apps
Reliability
Wireless service (cells) do not cover all areas, e.g. Mfg Sys Lab !
Human Computer Interface (HCI)
For small mobile devices, e.g. phones/PDAs, user-interface is an issue
Software:
Multi-purpose devices
Multi-tasking/threading, prioritizing and switching between processes
Common Mobile Phone OS‟s
Symbian OS (used by Nokia, Sony-Ericsson, …)
- Pre-emptive multi-tasking
- Closed source, Uses C++, Supports Java,
- App development requires certification
RIM Blackberry (used by Blackberry phones)
- Simple GUI, Optimized applications and HCI for email
Windows mobile (used by Samsung, AT&T, LG, Palm Treo)
- GUI emulates windows on PC
- Software development kit (SDK) is free for students, uses Visual C++, .NET
iPhone OS (used by Apple iPhones)
- Based on Apple OS X
- GUI: user friendly, touch-screen only (no keypad support)
Google Android (used by Google phone, HTC, …)
- Linux-based OS, Open source !
- SDK is free, uses Java
Comparing mobile apps with desktops..
What differentiates mobile apps from desktop apps ?
- Networked applications must deal with cellular communications
- Mobile OS (and apps have very limited resources:
Smaller size, Less RAM, Slower low energy CPU, Limited graphics,
RAM is smaller, …
mobile multimedia formats and file formats are different
- Mobile I/O systems are quite different from desktop ones
Touch-screen based, phone-keys based, reduced keyboard-based, …
Mobile Application Development: Case study - Android
Steps in Android Application development:
Download and install SDK
Develop the application: Eclipse IDE (Java, SQLite, XML)
Test the application: Android emulator
Register with Google (US$ 25)
Upload your application to Google App Store
Android OS Architecture
Phone users
App developers
Programmers
Hardware
developers
Structure of an Android Application
Android apps are
stored in „packages‟
Resources:
Data, sound files, images
java
java aapt MyApp.apk
data mp3
code
code
# library calls
Android OS is multi-processing, multi-threading multiple processes can
be running on the device at the same time.
Processes can communicate w/ the OS, and also can communicate w/ each other
Logical structure and life of an Android Application
An Android app is composed of a set of components
- Each component does a well defined activity
- Due to multi-tasking, multiple components could be doing something
at the same time
- An app may use a component from some other app, and/or it may
allow other apps to use some of its components
When an app is executed, Android creates a “virtual computer” in which
the process runs each process is isolated from others.
This is implemented via the DalVik Virtual Machine [Java Virtual Machine]
security
However, processes can share data with each other via special components
called „content providers‟
Android components: Activities
Activity is a sequence of related actions
Each activity presents a visual interface to the user
Each activity is derived from base class Activity
Each activity owns a View which controls a rectangular window;
Child views (controlling sub-rectangles) can be derived from parents;
Views are used to create images, icons, buttons, etc.
Examples:
The “Contacts” application may have an activity that displays a
scrolling list of all contacts listed by last name.
The “Calculator” app may have an activity that displays a numeric keyboard
and buttons for numeric operations, etc. and awaits inputs from the user.
Android API – activity control loop
Colored ovals: states of the activity
Grey rectangles: callback methods written by developer
source: developer.android.com
Android components: Services
Service is an activity that runs in the background no visual interface
Each activity is derived from base class Service
Example:
A common example of a service is an mp3 player that may run in the
background as the user may be involved with some activity of another
app, e.g. web browser.
Android API – service control loop
Colored ovals: states of the service
Grey rectangles: callback methods written by developer
NOTE:
Typically, a service may be created, say, by an activity;
Alternatively, a service may be started and running in some
other context, and can announce its interface to other activities –
in this case, the activity may just connect itself to the service,
in Android, this is called “bind”-ing to the service.
source: developer.android.com
Android components: Broadcast receivers
Broadcast receivers are similar to interrupt handlers in normal OS
BRs run in the background, listening for interrupts generated by other apps
An application may have one or more BR‟s to handle interrupts.
Examples of interrupts:
- Incoming phone call
- User changed language setting
- Battery is low
- User has transited from one time zone to different one
Android components: Content providers
Content providers make some subset of an application‟s data available
to other apps when requested
Content providers are the only mechanism for apps to share data.
Android application process
Process can be multi-threaded Android apps do not have a C-style “main”.
Activities, services, broadcast receivers: activated by messages called intents.
Content providers: activated by special objects called ContentResolvers.
Depending on the state of the application, and the user‟s actions, the app
may start (or terminate) some activity, or service, etc.
Before Android can start an application component, it must know
the name, location, and input types of the component The manifest
Notepad app
(partial manifest)
…
…
…
Views in Android
Most activities will present a „view‟ to the user, either to display some
graphics, or to get some user-input.
Thus each activity can create (instances) of one or more views. Each
view has some graphical objects that either fill the complete screen,
or a part of the screen.
Each object in a view, i.e. the layout, is also described in XML
Notepad app
Android app development: summary
The basic steps of developing an android app:
- Develop UML class diagrams, activity diagrams, use-case diagrams …
- Identify the activities, services, …
- For each activity, decide the GUI and design it, store as resources.
- Use the IDE (e.g. Eclipse), and program the Java code for each class
- Test & debug the code using the android emulator
- Upload the code on the mobile device.
Brief concluding remarks
Mobile Operating Systems are in some ways similar to desktop OS,
but there are several differences in details, and in usage.
Mobile app development process is almost similar to normal app development,
but issues such as compiled code size, memory usage and algorithm efficiency
are much more important.
Several modern mobile OS‟s are using xml as an integral part the programming
language – e.g. Android (manifest, view layout), Palm Pre OS, …
References and Further Reading
Mobile OS wikipedia
Google android developer site
Next: Project completion, Exam!
Case study: Hangman-style – „Save the bird‟ game
We consider a game similar to the popular „Hangman‟ game, with the
main difference being in the graphics (6 wrong guesses shark eats bird)