Creating Databases for Web Applications

Work session

Open Source versus Proprietary

important topics

HW: finish* projects. Look at final quiz guide. Final posting.

Final posting

• post your considered, reasoned opinion on Open Source vs proprietary; asp versus php; Access versus MySql; or any related issue.

• Catch up on other postings.

Postings: php vs asp, etc.

• Proprietary can be companies other than Microsoft. For example, Cold Fusion is product of Macromedia (formerly Allaire).

• Keep in mind that there are many topics, functions, relevant standards,etc. in these systems that we did not cover.

Things to consider

• … things to store away in the back of your mind for consideration when building a 'real' Web application.

Performance• Performance of Web sites governed by connection

AND site itself.– presence of large images, other large files, big

consideration.

• Some DBMS provide for stored procedures that carry out a query. Sometimes these can involve parameters. This is a way to improve performance. The function is compiled and not interpreted.

• Some DBMS provide for (extra) index fields besides the primary key. This is another way to improve performance.

Important topics

• multiple (concurrent) users of database– DBMS may handle this. – single table versus multiple tables– transaction concept

• writing/updating across multiple tables

• paging– handling of large[r] recordsets

Important topics, continued• scaling up application

– multiple users; many, many users– larger tables

• maintenance of program– version control– backup

• databases• scripts / code

– data base administrator• data dictionary

– 'quality assurance'• test suite• bug/feature list• investigate how bugs happen

Important topics, continued

• disaster control– backup data stores– backup procedure

• security– hackers– insiders

Note: security protections also help in benign situations: knowing where you need to look and where you don't need to look to uncover problems.

Reminder: Objectsare information + procedures

properties + methodsattributes + operatorsinformation + behavior

… can be defined by you, the programmer. DOM is the Document Object Model used for client side

(for example, document.write( ) ).asp is essentially a set of objects (Request, Response, etc.)

called the intrinsic objects.php support resembles other oo languages more than

JavaScript (maybe more than VBScript?)

php example (partial)class node {var $mparent; var $mfirstchild; var $mnextsib; var

$mname; var $mlocation; }function Node ($parent, $name, $location) {$this->mparent = $parent;$this->mname=$name;$this->mlocation=$location; }function addchild($child) {if isset($firstchild=$this->mfirstchild) {

$firstchild.addsib($child) }else {$this->mfirstchild=$child;} }function addsib($sib) { } }

ends class

constructor method

php example…$newnode = new Node (&$current, 'curley', 'NYC');

invokes a call to the constructor function node, which sets up an instance of a node.

… $current.addchild (&$newnode);this invokes the method of $current that will connect it to

$newnode.Access object properties: … = $current.mlocation;

see next

more php

• inheritance:– class specialcustomer extends customer { }

• overriding– re-use name of method

• reference operator (pointer)– $place = &$node; $place will refer to same thing, not a

copy

• eval ($string); evaluates the contents of $string.

JavaScript OO support• Limited, but can use functions in a var statement and

can name a procedure as a property.– connects data and code

• Neither php nor JavaScript has information hiding mechanisms– This is not for keeping something secret as much as for

catching an error during compilation that would otherwise lead to a logical, runtime error.

• no inheritance support– building objects from other objects to save redundant coding

AND have the system apply the appropriate procedure.

JavaScript OO support: basic

var node = new Object();

node.mname= "curley";

node.addchild=addchild;

a function defined elsewhere

JavaScript example: using constructor

function node (parent, name, location){this.mparent = parent;this.mname = name;this.mlocation = location; this.addchild=addchild;this.addsib = addsib;}

function addchild (child) { }function addsib (sib) { }

this is term for thing being created.

JavaScript example: usage

var person = new node (parent, 'moe','nyc');

parent.addchild(person);

… = person.mlocation;

Benefits of oo

• Encapsulates information and treatment of information to make code either to maintain and to re-use– only one place to check and to modify if you

need to change how you 'add a child' in the previous example.

– catches errors as compilation (syntactic) errors.

Emerging technologies, infrastructure

• broadband• wireless—smaller devices• WAP, XML, XSL, XSLT, WML• Application Service Providers• new/not so new offerings:

– Cold Fusion– asp.net, vb.net, Active X objects (for sale)– Open Source

• php 4.3.6 www.php.net

XML

• Building XML applications with Java– Large[r] applications requiring communication

between components

• Creating User Interfaces– xml and xslt, also wml, VoiceXML

Questions for final quiz

• See guide to final quiz posted online.

• Note: final will be open book, open notes. You do need to study.

Projects

• Prepare to demonstrate and to show your storyboard diagram (and maybe the others diagrams as reminders).

• Prepare hardcopy of diagrams plus choice essay if you needed to do one.

• Send URL of project to me!