WebBased DSS- Intro to internet & web applications

Model-View-Controller (MVC)

-Model: represents application data & business rules that govern data accessing updates -View: renders the user interface -Controller: interprets user actions & events and maps them into action in the model or the view

URLs (Uniform Resource Locators)

-URIs that start with http:// -contains info that directs a browser to the resource that the user wishes to access

Portable

-allows you to design web pages & applications that run across an enormous range of internet-enabled devices -internet & web programming technologies are designed to be this

Client-Side Scripting limitations

-browser dependency -restricted from arbitrarily accessing the local hardware & file system for security reasons -source code can be viewed by the client -sensitive information should not be on the client side -operations on the client can open web application to security issues

Server-Side Scripting limitations

-consume resources on the server -less efficient than client-side script -increase internet traffic

Multipurpose Internet Mail Extensions (MIME) type (text/html)

-content that the server is transmitting to the browser -specifies data formats (text/plain) -when browser receives this MIME type (image/jpeg), it attempts to display image~ image/jpeg

World Wide Web Consortium (W3C)

-founded by: Tim Berners-Lee -One primary goal: make web universally accessible -standards organization -web technologies standardized by W3C are call Recommendations -Current & forthcoming W3C Reccomdations: HTML5, CSS3, & XML

Examine the components of this URL http://www.deitel.com/books/downloads.html

-http:// == HTTP should be used to obtain resource -www.deitel.com == server's hostname, the name of the web server computer on which the resource resides (this computer is the host) -www.dietel.com == the hostname is translated into IP address -

Web page

-in simplest form is an HTML (HyperText Markup Language) document (with the extension .html or .htm) that describes to a web browser the document's content and structure

GET request

-typically gets or retrieves info from a server or search result based on a user-submitted search term -appends data to the URL (www.google.com/search?q=deitel), the ? separates the query string from rest of URL in a request -limits the query string (everything to right of ?) to a specific number of characters

POST request

-typically posts or sends data to a server -common uses: to send form data or documents to a server -sends form data as part fo the HTTP message, not part of the URL -best for lots of data bc no limit on query string characters -hides submitted data from user by embedding it in HTTP message

Client-Side Scripting

-used to validate user input, to interact with the browser, to enhance web pages, & to add client/server communication between a browser & a web server -uses computing resources of the client

HTTP version numbers

.9,1.0,1.1 (1.1 is most common)

Hypertext markup language endings

.html or .htm

World Wide Web

A collection of interlinked multimedia documents that are stored on the internet and accessed using the HTTP protocol

two most common HTTP request types (aka request methods)

GET & POST GET- gets or retrieves info from server, appends data to the URL POST-posts or sends data to server, sends form data as part of HTTP message, not as part of URL

Internet

Global system of interconnected computer networks; aka network of networks

Hyper Text Transfer Protocol (HTTP)

HTTP

Web servers

Make resources URL directs a user to available to web clients

the word GET in GET/books/downloads.html HTTP/1.1

a HTTP method indicating that the client wishes to obtain a resource from the path name

Middle tier..aka

aka..business logic tier -acts as intermediary between data in the information tier and application's clients -controller logic -business logic -presentation logic

Bottom tier..aka

aka..data tier or information tier -maintains applications data typically in relational database mgt system

Top tier..aka

aka..user interface tier or client tier

Server-side programming

applications that respond to requests from client-side web applications -such as: searching the internet, checking your bank account balance, ordering book from amazon, & ordering concert tickets

multitier applications (n-tier applications

divide functionality into separate tiers (logical groupings of functionality)

business logic

enforces business rules & ensures that data is reliable before the application updates a database or presents data to users

server-side scripting

have wider range of programmatic capabilities than their client side equivalents, more flexibility with this scrip which often generate custom response for clients

URI (Uniform Resource Identifier)

identifies a resource on the internet

Domain Name System (DNS) server

maintains a database of hostnames and their corresponding IP addresses & performs the translations automatically

Web Servers

make such resources available to web clients

Web

one of the services communicated via the internet (email is another example)

controller logic

processes client requests (such as requests to view a product catalog) and retrieves data from the database

presentation logic

processes data from information tier and presents the content to the client

the remainder after the word GET GET/books/downloads.html HTTP/1.1

provides the path name of the resource and the protocol's name & version number

Cache

save on disk, for recently viewed web browsers for quicker reloading

Client-Side programming

technologies are used to build web pages and applications that are run on the client (in the browser on the user's device)

Hyperlinks

when click load a specified web document. HTML documents normally contain these. Can be images, text, webpage, email address, files, etc -when clicked, a web request is sent to a web server