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CIT3100 – Internet Programming III Web Applications Lesson 1 (28 Sep 05) Fernando J. Maymí [email protected] 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 HTTP/1.1 GET /file.html 200 OKHTTP/1.1 <CR><LF> Host: www.google.com Content-Type: text/html <CR><LF> <html><body>...</html> Simple HTTP Request Internet Web Server Web Client GET HTTP/1.1 HTTP/1.1 200 OK Content-Type: text/html <html><body> <img src=“img/happyface.gif”> ...</body></html> GET img/happyface.gif HTTP/1.1 HTTP/1.1 200 OK Content-Type: img/gif /9j/4AAQSkZJRgABAQAAAQABAAD/2w BDAAgGBgcGBQgHBwcJCQgKDBQND... 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 HTTP With JavaScript Internet Web Server Web Client GET /hello.html HTTP/1.1 HTTP/1.1 200 OK Content-Type: text/html <html><head> <script language=“JavaScript”> <!-alert(“Welcome to my world”) --> </script> </head><body>...</body></html> 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 HTTP on Demand Internet Web Client GET /hello.php HTTP/1.1 1. Web server loads the script from its file system Web Server 2. Web server passes the script to the interpreter 3. The interpreter runs the script and passes its output to the web server HTTP/1.1 200 OK Content-Type: text/html <html><body> <img src=“img/happyface.gif”> ...</body></html> 4. The web server blindly passes the output to the client 3-Tier Architectures 3 Tiers are: Web Client Web Server Database Server Essential for scalability Enhances security Data-driven HTTP Request Items Internet Web Server Web Client GET items.php HTTP/1.1 PHP Engine HTTP/1.1 200 OK Content-Type: text/html <html><body><h1>Items</h1><tab le><tr><td>Widget</td><td>$50. Database Server SELECT name, price FROM items Widget,50.0 Nails,0.05 Bolts,0.10 Your Turn… Download and install the Paros proxy http://www.parosproxy.org/download.shtml 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 Planning Identifying business value Analyze feasibility Develop work plan Staff the project Control and direct project Analysis Analysis Information gathering Process modeling Data modeling Design Physical design Architectural design Interface design Database and file design Program design Implementation Construction Installation Processes and Deliverables Process Product Planning Project Plan Analysis System Proposal Design Implementation 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
