Internet Applications

Spring 2008

Review

• Last week– XHTML, Webservers

This week

• Tech-topic presentations - XML/RSS

• Introduction to programming

XML DC record<?xml version=“1.0” encoding=“UTF-8”?><!DOCTYPE qualifiedDublinCore PUBLIC '-//OCLC//DTD QDC v.1//EN'> <qualifiedDublinCore>

<Creator>Alliance of Baptists</Creator><Title>Alliance of Baptists Records, 1987 - 2001</Title><Source/><Language>en</Language><Coverage>2.1 linear feet</Coverage><Description>[Lots of text omitted]<Description><Rights>Collection is open.</Rights><Subject>Alliance of Baptists</Subject><Subject>Southern Baptist Alliance</Subject><Contributor/><Publisher>Z. Smith Reynolds Library, Wake Forest University</Publisher><Type>text/xml</Type><Relation>Alan P. Neely Papers, Z. Smith Reynolds Library, Relation><Identifier>http://zsr.wfu.edu/collections/digital/ead/allianceofbaptists.xml</Identifier>

</qualifiedDublinCore>

Encoding Schemes (XML)

• Required syntax– Document type declaration

• <!DOCTYPE food SYSTEM "food.dtd"> • Optional but useful

– Processing instruction• <?xml version="1.0"?>

– Elements• <elementname></elementname> notation• All elements must be closed <ex></ex> or <ex/>

– Attributes• <element attribute=“attributevalue”/>• Attributes must be enclosed in “”

– Text• <ex>fieldcontent</ex>

Encoding Schemes (XML) - 2

• File attributes– Elements are repeatable (if allowed by

DTD/Schema)– An XML file can contain multiple “records” – Certain characters like need to be

represented by escape sequences:• & = &amp;• &lt; = <• &gt; = >

Encoding Schemes (XML) - 3

<?xml version="1.0"?> <rss version="2.0">

<channel> <title>Sample RSS File</title><link>http://urltofile.xml</link> <description>This is a sample</description> <language>en-us</language> <pubDate>Tue, 10 Jun 2003 04:00:00 GMT</pubDate> <item>…</item><item>…</item><item>…</item><item>…</item>

</channel>

</rss>

XML Components

• XML data model definition– Document Type Definitions (DTD)– XML Schema– Application Profiles

• XSL processing instructions– Transformation to new format– Powerful enough to serve as a simple

application development platform

RSS Example<?xml version="1.0" encoding="UTF-8"?><rss version="2.0"><channel>

<title>NYT > Media and Advertising</title><link>http://www.nytimes.com/pages/business/media/index.html?partner=rssnyt</link><lastBuildDate>Tue, 26 Feb 2008 13:05:01 GMT</lastBuildDate>

<item><title>Nielsen Looks Beyond TV, and Hits Roadblocks</title><description>Nielsen wants households to let it eavesdrop on Web surfing and cellphone

use, but it is finding it a tough sell.</description><author>LOUISE STORY</author><guid isPermaLink="false">http://www.nytimes.com/2008/02/26/business/media/

26nielsen.html</guid><pubDate>Tue, 26 Feb 2008 12:46:15 GMT</pubDate></item>

</channel></rss>

http://cyber.law.harvard.edu/rss/rss.html

DOM Example

•A Hierarchy of elements

•Family based inheritance

•Parent

•Child

•Sibling

•Element access by name

•document.getElementById("You")

Programming

• Definitions

• Concepts

• A programming framework

Definitions

• Programming Language• “A formal language used to write instructions that can be

translated into machine language and then executed by a computer.” (definitions)

• Scripting Language• Run-time (does not require compilation)• Restricted context (requires a specific environment)• Functional / Object oriented • Definitions

• Compiler / Interpreter• A program that builds and executes a program.

Compilers create a self-executable file, interpreters read a text script at run-time

Programming approaches

• Logical/structural programming• Stream of consciousness• Starts at line 1

• Procedural programming• Uses functions, sub-functions, subroutines• Encapsulation, modularization

• Object-oriented programming• Further encapsulation• Uses concepts of inheritance, modularity

The programming process

• Analyze the problem• What do you want your program to do?• What are your users expecting, what data do you have?

• Plan program flow/logic • What steps need to occur, in what order?• Useful tools include Step-Form, flowcharts, and

pseudocode

• Code the program• Create variables, routines, functions

• Compile/run the program• Test, verify• Release

Algorithms

• “An effective procedure for solving a problem in a finite number of steps.”

• Sample Algorithm for an email form (Step Form)– Begin

• If form data is present then continue processing– Get data from form (Subject, note, etc)– If the subject doesn’t contain bad stuff then continue

processing» Write subject, note to email function» Send email» If Email sent successfully then tell user that it did,

otherwise output the error code

– End

Algorithm elements

• Processes / Sequences• Actions are ordered according to need

• Decision making / Selection• If...Then...Else

– If today is Friday then go home early– If username = mitcheet then allow access

• Repetition / Iteration / Looping• While

– While the database returns data, print it out

• Foreach– For Each piece of data returned, write it to a file

• Variables• Placeholders for information to be used by program• Often “initialized” with specific values (such as 0”

Creating an Algorithm

• Investigate– Identify a specific process

• (sending email)– Identify the major decisions

• (presence of data, appropriateness of data)– Identify the loops

• What needs to happen several times?– Identify variables

• Lay out the algorithm– Design a sequence of steps incorporating the decisions from

step 1. Make changes as necessary• Refine algorithm

– Implement changes noticed during run-through– Group processes, variables

Decision making

• Single-Alternative / unary outcome– If then

• Dual-Alternative / binary outcome– If then else

• Multi-Alternative /x-ary outcome– If then elsif elsif elsif– Switch case statements

• Switch case1: case2: default:

Flowchart Examples

• Start / End

• Data

• Decision Making

• A process

Pseudo code• Input/output

– Input, Read, Display

• Iteration– Repeat Until, Dowhile /end dowhile, for/end for

• Decision– If <condition> then <statement> else– If <> then <> elsif <> elsif <> endif

• Processing– Add(+), subtract(-), compute, compare (<,=,>), set

• Subroutines (functions/sub-functions)– Use to define sub processes:

• EMAILTHIS: – Input email, subject, note– Send email– Set send result to output variable X– return X

• Include in your pseudo code with a call statement– Call EMAILTHIS (email, subject, note)

PHP Overview

• Standard PHP Syntax review– Structure, operators,

• Constructs needed for today– Variables

• Scalar, Arrays, Objects

– Output• Echo

– Loops• Foreach, for($i)

– Built-in Functions• DomXML functions

Language elements (Syntax)

• Syntax – grammar, order, structure of program– PHP syntax example

<? PHPFunction () { stuff }$variablename;End of Line markers (;)//comments

?>

– Syntax has to be perfect!– PHP is case specific

Standard PHP program<html stuff.....>

<?php //Beginning element

Example statement; //Use a semicolon to end lines

$myvalue; //A scalar variable

$myarray[1]; //An array with value 1 returned

$myObjectref->function() //A function in an object

$myvalue = “hello”; //Variable Assignment

echo (“stuff”); //A standard PHP Function

?> //Ending Element

<html stuff.....>

Variables

• Text – Strings

• Numbers– Integers (whole numbers)– Floating point – (decimal numbers)

• Boolean– True/False

Variables – single value

• Scalars – Single value variables– Strings - $username = “mitcheet”– Numbers $cost = 55.00– Boolean $ready = True

Variables – multiple values

• Arrays – Multi-value variables – Grouped in numerical order

• $email[1] = “mitcheet@unc.edu”• $email[2] = “burrohj@unc.edu”

– Grouped with text• $email[1][“username”] = “mitcheet@wfu.edu”• $email[1][“realName”] = “Erik Mitchell”

– General syntax• $email = array ( key=>value, key=>value)• Arrays can be nested (think hierarchy)

Objects

• Objects components– Methods (Functions)– Fields (Variables)

• PHP syntax for objects– $myObjectReference->fieldvalue– $myObjectReference->objectFunction()

• DomXML Example– $dom = domxml_open_file("http://....xml");– $rsstag = $dom->get_elements_by_tagname("rss");

PHP Variable Operators

http://www.w3schools.com/php/php_operators.asp

PHP Comparison Operators

http://www.w3schools.com/php/php_operators.asp

Variable scope

• Depending on where you initialize a variable, impacts what functions can use it– A variable initialized at the beginning of

your file is “global”– A variable initialized within a function is

limited to the function.

PHP Output functions

• echo ‘my output text’;– You can use ‘ or “ but they have special

meaning

• echo ‘my output’.$variable.’my output’– Use the . To concatenate strings

• Debugging output– print_r ($complexvariable)

• Prints a user readable array/object

Exercise 1

• Sample Program– http://www.ils.unc.edu/~mitcheet/class_7ex

ercises/class7_ex1.txt– Type in this program– Upload to Ruby– Run and look at sourcecode– Try to create an echo statement that

outputs specific values of the variable• echo $associativeArrayVariable[‘title’]

Looping

• Definition• Loop structures allow re-execution of instructions with

multiple sets of data

• Examples• Writing records from a database query onto a webpage• Calculating cost, discounts, shipping on items in a

shopping cart• Comparing values to make decisions

• Benefits• declare logic and operational statements once & re-use• Loops are the building blocks of structured programming• Use a ‘main’ loop to control the program

Loop structures

• Components• Loop control variable

– the variable that keeps changing ($i for example)

• Sentinel value– the value which signals the end of the loop

• Loop control structures– Do while, While, for, foreach

• Examplefor($i=1; $i<=100; $i++) {

echo “hello world! <br/>”;

}

for() { } Control structure$i = 1 Variable declaration$i < 100 Limit declaration$i++ Increment declarationecho “”; operational statement

Nesting

• Use a mix of flow-control and decision making functions to create complex processes

• If -> then -> else

• Switch -> case -> default

• For -> next

• Do -> while

Functions

• Definition– “A sequence of instructions for performing a

specific task” (freedictionary)• Benefits

– Modularization/Abstraction– Code re-use– Variable management (global, local)– Easier to troubleshoot and maintain

• Key concepts– Global variables vs local variables– Parameters– Returned values

PHP Functions

• Examples– Phpinfo(), for(), foreach(), echo.......

• Contents– Name, Parameters, operations, return values

function myFunctionName (parameters)

{

parameters;

operations;

return variables;

}

Declaration

{

Parameters passed to functionOperations (calculate, lookup, etc)Return values to rest of program

}

The XMLParse object

• SimpleXML– Standard in PHP5, but we are using PHP4 – Today, we are relying on some extra code to make

things simple!

• What it does– Reads in an XML file and breaks the DOM into an

array of variables– Provides us methods to access XML values

• http://www.criticaldevelopment.net/xml/doc.php

XMLParse Example<?php

// Include the code that makes simplexml workrequire('./php_4_simplexml.php');

//Get the XML document loaded into a variable$xml = file_get_contents('http://www.nytimes.com/services/xml/rss/nyt/Music.xml');

//Set up the parser object$parser = new XMLParser($xml);

//Work the magic...$parser->Parse();

//Echo the plot of the first <movie>echo $parser->document->rss[0]->channel[0]->title[0]->tagData;

//Echo the plot of each <item> titleforeach($parser->document->channel[0]->item as $item)

{echo $item->title[0]->tagData;}

?>

XMLParse Example (2)

• Mixed array/object syntax– $parser->document->channel[0]->item

• Available functions for an object– tagData – tagParents – tagChildren – tagAttrs – tagName

Exercise 2

• In this example, we will create a simplexml object and process some data– Get the SimpleXML file and and upload it to

your webspace– Write the simplexml example program

Exercise 3 / homework

• Today we will add RSS feed parsing functionality to our webpage from last week– Create a program outline using

pseudocode/flowcharting– Using the XMLParse functions, write the program

in php– Program requirements

• Use XMLParse or another solution (DOMXML is much more complicated but uses only embedded php functions)

• Your program should be able to output multiple RSS feeds (looping).

• Your program should only show the first 10 elements of the feed and provide a link to view more

Next week

• Technology Topics CSS/XSLT

• More on PHP