CIT3100 – Internet Programming III Web Applications Lesson 1 (28 Sep 05) Fernando J. Maymí

Agenda for tonight Introductions  Who we are, and  What do we want to be when we grow up? World-Wide Web Communications Web Application Development User Interface Design

How the World Wide Web Communicates

Hyper-Text Transfer Protocol Defined in RFC 2616 (for version 1.1) Encapsulated in a TCP segment Request/response message protocol  Command  Blank line  Header fields  Blank line  Message GET /file.html HTTP/1.1 Host: HTTP/ OK Content-Type: text/html...

Internet Web Client Web Server Simple HTTP Request GET HTTP/1.1HTTP/ OK Content-Type: text/html... HTTP/ OK Content-Type: img/gif /9j/4AAQSkZJRgABAQAAAQABAAD/2w BDAAgGBgcGBQgHBwcJCQgKDBQND... GET img/happyface.gif HTTP/1.1 Hello

Client-Side Scripting Client scripts are interpreted by the web browser Client scripts can:  Alter the appearance of the document  Validate form fields  Perform general computational tasks Client scripts can be embedded or attached

Internet Web Client Web Server HTTP With JavaScript GET /hello.html HTTP/1.1HTTP/ OK Content-Type: text/html <!-- alert(“Welcome to my world”) -->... The client browser parses the HTML, finds the script and executes it locally JS

Server-Side Scripting Server scripts are interpreted by the web server Common languages are  PHP  ASP  JSP  Perl Server scripts produce HTTP data

Internet Web Client Web Server HTTP on Demand GET /hello.php HTTP/1.1HTTP/ OK Content-Type: text/html The web server blindly passes the output to the client 1. Web server loads the script from its file system 2. Web server passes the script to the interpreter 3. The interpreter runs the script and passes its output to the web server

3-Tier Architectures 3 Tiers are:  Web Client  Web Server  Database Server Essential for scalability Enhances security

Internet Web Client Web Server Data-driven HTTP Request Items GET items.php HTTP/1.1HTTP/ OK Content-Type: text/html Items Widget $50. SELECT name, price FROM items Database Server Widget,50.0 Nails,0.05 Bolts,0.10 PHP Engine

Your Turn… Download and install the Paros proxy  Setup your browser to use it as a proxy Enable trapping of both requests and responses Visit your favorite web site and see what happens

Web Application Development

Project Phases Planning  Why build the system? Analysis  Who, what, when, where will the system be? Design  How will the system work? Implementation  System delivery

Identifying business value Analyze feasibility Develop work plan Staff the project Control and direct project Planning

Analysis Information gathering Process modeling Data modeling Analysis

Physical design Architectural design Interface design Database and file design Program design Design

Construction Installation Implementation

Processes and Deliverables ProcessProduct Planning Analysis Design Implementation Project Plan System Proposal System Specification New System and Maintenance Plan

Designing the User Interface

Principles of UI Design Layout Content awareness Aesthetics User experience Consistency Minimal user effort

Layout The screen is often divided into three boxes  Navigation area (top)  Status area (bottom)  Work area (middle) Information can be presented in multiple areas Like areas should be grouped together

Layout (cont’d) Areas and information should minimize user movement from one to another Ideally, areas will remain consistent in  Size  Shape  Placement for entering data  Reports presenting retrieved data

Layout Example 1

Layout Example 2

Content Awareness All interfaces should have titles Menus should show  where you are  where you came from to get there It should be clear what information is within each area Fields and field labels should be selected carefully Use dates and version numbers to aid system users

Aesthetics Interfaces need to be functional and inviting to use Avoid squeezing in too much, particularly for novice users Design text carefully  Be aware of font and size  Avoid using all capital letters

Aesthetics (cont’d) Colors and patterns should be used carefully  Test quality of colors by trying the interface on a black/white monitor  Use colors to separate or categorize items

User Experience How easy is the program to learn? How easy is the program to use for the expert? Consider adding shortcuts for the expert Where there is low employee turnover, some training can lessen the impact of less precise interfaces

Consistency Enables users to predict what will happen Reduces learning curve Considers items within an application and across applications Pertains to many different levels  Navigation controls  Terminology  Report and form design

Minimize Effort Three clicks rule  Users should be able to go from the start or main menu of a system to the information or action they want in no more than three mouse clicks or three keystrokes

UI Design Process

Use Scenario Development An outline of steps to perform work Presented in a simple narrative Document the most common cases so interface designs will be easy to use for those situations

UI Structure Design Window navigation diagram (WND)  Shows how all screens, forms, and reports are related  Shows how user moves from one to another  Like a state diagram for the user interface Boxes represent components Arrows represent transitions Stereotypes show interface type  Remember the diagram represents what will be shown to the user, NOT what the system is doing to make it work!

WND Example

Your Turn… Develop the WND for the Online Banking system