5.1. Web

In this lecture we look at...
[Section notes PDF 133Kb]

5.1.01. Databases for the Internet

Path from DB to User
Information flow
Data formats (OO)
Format transitions
Limitations/channel
The Future

5.1.02. OO

Object orientated approach

Consistent/optimised development model
Good approximation of real world
Closer link to mini-world

Java and PHP
DB persistence
UML

5.1.03. Java and PHP in context

Java

JSP (server-side)
Javascript (client-side)

PHP

Server side only

JSON or XML

Object communication

Ideal scenario

Java – load times

5.1.04. In a perfect world

Homogenous data format/data model
DB stores objects instead
Objects transferred

Robust
Lightweight
Fast
Consistent (more later in Transactions)
Caching

5.1.05. In the real world

Heterogenous data model
Object translation/wrappers
Different languages features at different layers
Minimal subset of OO functionality available end-to-end
Going to look at information flow/functionality provided

5.1.06. User

Limitations of being human

short term memory
long term familiarity

language of the Internet

hypertext linking
form filling

Advantages of being human

impatience, no waiting
wants instant response

5.1.07. Browser

Http requests
Forms

Post
Get

Form fields

By name, by ID
Hidden

Javascript/DOM tree

5.1.08. Internet

Communication medium
Good for transferring data
Not good for transforming data
e.g. Light in air
e.g. Signal over CAT5e/UTP cable

5.1.09. Web server

Straight HTML pages
Dynamic HTML pages

PHP example
JSP example

As above with RDBMS integration

PHP PDO example

As above with Objects

PHP DBDO example

5.1.10. load, edit, submit, act timeline

5.1.11. href click, versus form post

Protocol stack
Basic up-down
Shortcuts
Browser cache
Web server

assembled page cache
php object cache

DB optimised queries

5.1.12. Examples from the web