IELM 511: Information System design

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10 Δεκ 2013 (πριν από 3 χρόνια και 6 μήνες)

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IELM 511: Information System design

Introduction

Part 1. ISD for well structured data


relational and other DBMS

Part 2. ISD for systems with non
-
uniformly structured data

Part III:
(subset of)

Basics of web
-
based IS (www, web2.0, …)

Markup’s, HTML, XML

Design tools for Info Sys: UML

API’s for mobile apps

Security, Cryptography

IS product lifecycles

Algorithm analysis, P, NP, NPC

Info storage (modeling, normalization)

Info retrieval (Relational algebra, Calculus, SQL)

DB integrated API’s

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 I/O systems are quite different from desktop ones


Touch
-
screen based, phone
-
keys based, reduced keyboard
-
based, …

mobile multimedia formats and file formats are different

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

MyApp.apk

java

code

java

code

data

mp3

Resources:


Data, sound files, images

# library calls

aapt


Android apps are
stored in ‘packages’

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.

source: developer.android.com

Android

API



activity

control

loop

Colored ovals: states of the activity


Grey rectangles: callback methods written by developer

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.


source: developer.android.com

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.

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
:

Broadcast

receivers

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

components
:

Content

providers

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.

Android

application

process

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

<?xml version="1.0" encoding="utf
-
8"?>

<manifest package="com.example.android.notepad" …>


<application android:icon="@drawable/app_notes" android:label="@string/app_name" >


<activity android:name="NotesList" android:label="@string/title_notes_list">


<intent
-
filter> <action android:name="android.intent.action.MAIN" />



</intent
-
filter>


<intent
-
filter>


<action android:name="android.intent.action.VIEW" />


<action android:name="android.intent.action.EDIT" />


<action android:name="android.intent.action.PICK" />



</intent
-
filter>





</activity>


</application>

</manifest>


Notepad app

(partial manifest)

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

Views

in

Android

<?xml version="1.0" encoding="utf
-
8"?>

<view xmlns:android="http://schemas.android.com/apk/res/android"


class="com.example.android.notepad.NoteEditor$LinedEditText"


android:id="@+id/note"


android:layout_width="fill_parent"


android:layout_height="fill_parent"


android:background="@android:color/transparent"


android:padding="5dip"


android:scrollbars="vertical"


android:fadingEdge="vertical"


android:gravity="top"


android:textSize="22sp"


android:capitalize="sentences"

/>

Notepad app

(layout of Note
-
Editor)

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.

Android

app

development
:

summary

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, …

Brief

concluding

remarks

References

and

Further

Reading

Next: Project completion, Exam!

Mobile OS wikipedia


Google android developer site

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)