web-based applications are often
multitier applications that divide functionality into separate tiers
tiers of web-based applications typically reside on
separate computers
bottom tier: aka and purpose
- data tier or info tier
- maintains application’s data
middle tier
implements business logic, controller logic and presentation logic to control interactions between application’s clients and its data
business logic in the middle tier
enforces business rules and ensures that data is reliable before the server application updates the database or presents data to users
business rules
dictate how clients can and cannot access application data, and how applications process data
top tier/client tier
application’s user interface
in response to user actions, the _______ interacts with the _______ to make requests and to retrieve data from _________. ________ then displays data retrieved for the user.
client tier, middle tier, information tier, client tier
the top tier is ______ + ex
static or dynamically generated content rendered by the browser (front-end)
- HTML, CSS, JavaScript, jQuery
logic tier is an _____ + ex
application server for dynamic content processing and generation (middleware)
- Python, PHP, Java EE, ASP.NET
data tier is a ________ + ex
DBMS that manages and provides access to the data (back-end)
- mySql, Sql Server, Oracle, DB2
client-side scripting can
- validate user input
- interact with browser
- enhance web pages
- add client/server communication between a browser and a web server
limitations of client-side scripting
- browser or scripting host must support scripting language and capabilities
- sensitive info (passwords) cannot be stored or validated on the client
- placing large amounts of Java on the client can cause security issues
server-side scripting languages have a
wider range of programmatic capabilities
limitations of server-side scripting
- increased demand for computing resources on the server
- increased network traffic
- dependent on a network connection
to request documents from web servers,
users must know the hostnames on which the web server software resides
users can request documents from
local web servers or remote web servers
local web servers can be accessed through the name
localhost
localhost
a hostname that references local machine and normally translates to IP address 127.0.0.1 (aka loopback address)
remote web server can be accessed by
domain name (which is translated to IP address by Domain Name Servers) or an IP address
