Web Services,
Mashups, & QueryPath
Drupal Camp WI, 2009

Matt Butcher
First web app: 1995
About a dozen languages
Five books, dozens of articles
Milkshake problem

2009
2004

What We’ll Cover
• QueryPath: What it is and how it works.
• Web services and QueryPath
• QueryPath in Drupal
• Mashing Stuff Up

A PHP library designed to make working with
XML, HTML, and HTTP
simple, powerful, and robust

What are people doing
with QueryPath?

Designer/Developer
Dilemma
• Designers create HTML
that is pixel perfect
• Developers are charged
with taking design and
turning it into a web
tool.
• But developers don’t
have the designer’s
skillset.

TweetyPants.com

Bridge Layers
• Data silos are bad, repositories are good
• Import and export
• Information is shared using XML

Parsing ODT Files
<?php
require 'QueryPath/QueryPath.php';
$odt = 'zip://o.odt#content.xml';
foreach(qp($odt, 'text|h') as $i) {
print $i->text() . \"\\n\";
}

Web Services
Flickr, YouTube, Amazon, Twitter, e-
Commerce providers, Calias,
OpenAmplify, DBPedia,
MusicBrainz, Technorati...
REST, SOAP, XML-RPC, Linked
Data, SPARQL...

Simplicity

The Task
Find all
<a></a>
tags who have
the ancestor
<div></div>

The DOM API
• At least seventeen
classes, each with dozens
of methods.
• Complex data structure.
• Checkered history in
PHP.
• VERY powerful.

SimpleXML
• One class, about a dozen
functions and methods.
• Turns XML into basic
objects.
• Makes easy stuff easy,
and makes everything
else insanely hard.
Same size as DOM
Example

SAX / Expat
Same size,
fewer features
• Event based.
• Write your own parser
handler.
• One per XML format.
• Only reliable “legacy”
library.

QueryPath
• Compact library.
• Functions are short and
mnemonic.
[This space intentionally left blank ]
• The power of DOM, but
simpler than SimpleXML
• (Shhh... don’t tell, but it’s
built on the DOM.)

Anatomy of a
QueryPath

Powerful

The Features
• Query a document • Access remote data
• With XPath • Extensions for...
• CSS selectors • Advanced XML
manipulation (XSLT,
• Move around inside the XSD, PI)
document
• SQL database access
• Modify the document
• Templates
• Access local files

CSS 3 Selectors
Source: “Using the QueryPath PHP Library.” Matt Butcher. IBM developerWorks. Mar. 28, 2009
Use CSS Selectors (like in stylesheets) or XPath queries

Traversing an
HTML or XML
Document
There are over a dozen
functions for traversing a
document.
These are similar to jQuery’s
traversal functions.

Manipulating a
Document
• Get and set text,
elements,
attributes, etc.
• Move, clone,
delete.
• Build arbitrary
XML or HTML.

Work with local or
remote sources
• HTML • SPARQL
• SVG images • SOAP
• RSS or Atom • Open Office docs
• Flickr • DBPedia
• Twitter • MusicBrainz
• RDF/Linked Data • ...

Extensibility
• One library cannot
provide everything.
• But it can provide an
extension mechanism.
• Developers can integrate
their own code easily.
• You provide the kitchen
sink.

Built-in Extensions
• QPDB: QueryPath SQL Database layer
• QPTPL: Template support for QueryPath
• QPXML: Extensions for serious XML
hacking
• More...

Twitter Search
Ten Lines of Code

Drupal Module

The Kewpie Demo
• QueryPath module
• QP Cache module
• Amplify module
• QP Services module

Demos
Instant Portal video:
http://www.youtube.com/watch?v=GBBKPIva1tM
Twitter Rating (TweetyPants):
http://tweetypants.com

Learn More
• QueryPath.org
• Technosophos.com
• IBM developerWorks
• Drupal.org/project/...
• querypath
• amplify
• qpservices

Questions?
Matt Butcher
http://twitter.com/technosophos
http://technosophos.com