XSLT & XPATH
From Friday
• Everything in XML is machine readable
• Attributes describe elements, so does an
element’s place in the tree (context)
• XML must be
– Well formed (following XML syntax rules)
– Valid (following the rules of the specified DTD[s])
Your resume should look like:
Question
• How can copyright & attribution information
be maintained in mashups?
Using Meta Data in Decisions
Or
Why bother with structured markup?
facilitate (re)usability by others
Image an Article:
Title
creator
Featured image?
body
HTML
RDFa
• Resource Description Framework in [xhtml]
attributes
Down Stream Uses of Structure
Currently, FB guesses at what the
‘featured’ image might be when you
Post a link. Wouldn’t it be better if
tumblr told FB?
Down Stream Uses of Structure
Provenance
Provenance :: where
something came from
… wouldn’t be nice if
tumblr style provenance
Was inter-system
Question
• How can copyright & attribution information
be maintained in mashups?
XSLT & XPATH
• XPATH = XML query language
• XSLT = Translate XML from one schema to
another
– Extensible Stylesheet Language Transformations
• XSLT is nothing without XPATH
XPATH
•
•
•
•
XSLT
CSS (sorta)
jQuery (sorta)
PHP SimpleXML
Get an RSS File
• Example: nytimes.com
• Click on RSS button
– (see the rss being transformed into HTML by the
browser)
• View Source
XPATH Selectors
//
selects the root element
channel
selects the channel element and all of its children
//channel/title
/ moves down the tree and selects the title element
XPATH Selectors
title/..
selects channel
/.
selects the current element (if you're in a loop or
something)
XPATH Selectors (attributes)
@
selects nodes attributes
channel/link/@type
selects the type attribute in link
XPATH Conditionals
go in []
//channel/item[1]
selects the first item
[last()]
[position()<15]
//a[@href="http://www.rpi.edu"]
XPATH Operators & Comparators
+ - * div = < > >= <= or and mod
| is not OR it is used to concatenate sets of
elements
XPATH functions
•
•
•
•
•
•
•
•
position()
last()
abs()
floor()
string-length()
name()
http://www.w3.org/TR/xpath-functions/
http://www.w3schools.com/Xpath/xpath_functio
ns.asp
XPATH
• Get, run, files from:
– http://www.rpi.edu/~gillw3/websys/xslt/files/
• (inspect both, open the RSS file in your
browser)
XSLT
• XSL is XML
• Transforms XML into XML
• We'll transform XML into XHTML
XSLT
• Where does XSLT happen?
– server side:
http://us2.php.net/manual/en/book.xsl.php
– Client side: FF / Safari / IE
add to the top of your xml document
<?xml-stylesheet type="text/xsl" href="trasnform.xsl"?>
XSLT
• Use XPATH to select (and display) element
values
• XSLT value-of
• <xsl:value-of select=" XPATH HERE "/>
• <xsl:value-of select="channel/item[1]/title"/>
XSLT Control Structures
•
•
•
•
•
If
Choose / when / otherwise
for-each
sort
templates
XSLT if
<xsl:if test="creator=‘someone’">
<li>
<xsl:value-of select=“title"/>
</li>
</xsl:if>
XSLT Choose
<xsl:choose>
<xsl:when test=“XPATH">
output
</xsl:when>
<xsl:otherwise>
output
</xsl:otherwise>
</xsl:choose>
May stack many
tests / conditions
XSLT for-each
<xsl:for-each select="xpath here">
<xsl:for-each select="channel/item/">
<li> <xsl:value-of select="title"/> </li>
</xsl:for-each>
XSLT Sort
<xsl:sort select="title"/>
<xsl:for-each select="channel/item/">
<xsl:sort select="title"/>
<xsl:value-of select="title"/>
</xsl:for-each>
• Datatype & order attributes:
http://www.xml.com/pub/a/2002/07/03/transform.html
XSLT Templates
• Template is a container for a chunk of XSLT
• XPATH inside of the template starts where the
match attribute ends
<xsl:template match=“XPATH">
stuff: output & control
</xsl:template>
XSLT Templates
• Templates As Functions
<xsl:template match=“channel/item">
<xsl:call-template name=“item-display"/>
<xsl:param name="title">
value
</xsl:param>
</xsl:call-template>
</xsl:template>
In Class
• Grab this XML feed:
http://events.rpi.edu/webcache/v1.0/xmlDays
/3/list-xml/no--filter.xml
• Using XPATH and XSLT:
– Print out a list of events from the feed
– Put the summary in an <H3>
– Put the description in a <P>
– Include a human readable start time & date