Playground page for the XML Course

For practical exercises, the XML software is installed in the IFI CIP Pool.

XML examples
XML tools
XHTML
XPath
XQuery
XSLT
XML schema
SQL/XML
RDF
tomcat/Web Services

XML Tools and Links

Browsing, editing

Browsing: Use mozilla/firefox: for looking at XML instances.
XML instances that are not HTML/XHTML are presented by their XML structure - then you can click subtrees to open or close.
Editing: kxmleditor.

Validation, Navigation, Exploration

xmllint
- xmllint -loaddtd -valid --noblanks -noout filename validates a given file against the DTD given in its DocTypeDecl (--noblanks ignores ignorable (indentation) whitespace, which would not be allowed in non-mixed contents).
- xmllint -noout -schema schemafilename file.xml validates a given file against an XML Schema.
- xmllint can also be used for actually navigating inside an XML instance:
  - call xmllint -loaddtd -shell filename.
    Then, the following commands are allowed:
  - validate does a (somewhat sloppy) validation.
  - pwd gives the current path.
  - cat outputs the current node in ASCII.
  - cat xpath-expr ouputs the result of evaluating the xpath-expr wrt. the current node.
  - cd xpath-expr navigates to the node addressed by xpath-expr bezeichneten Knoten. xpath-expr must result in a single node.
  - du xpath-expr lists the contents of the current node.
  - dir xpath-expr gives nodetype and attributes.
  - try the following example session:
```
          xmllint -shell mondial-europe.xml
          pwd
          cat //country
          cat //country/name
          cat //country[name="Germany"]
          cd //country[name="Germany"]
          pwd
          cd province[9]
          du
          cat name
          dir
          cd id('cty-Germany-Hannover')
          cat
          pwd
```
- with saxon (see Section on XQuery) call saxonXQ -dtd:on -s:filename xpath/xquery expression filename.
```
    saxonXQ -dtd:on -s:mondial.xml bla.xq
   
```

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XHTML

XHTML 1.0/HTML 4.01 is described at http://www.w3.org/TR/html/.
DTDs of XHTML 1.0 for downloading can be found here.

Usually, the DTD on the W3C server is referenced by

    <!DOCTYPE html PUBLIC
       "-//W3C//DTD XHTML 1.0 Strict//EN"
       "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

Note that this DTD associates a namespace with XHTML documents via

        <!ELEMENT html (head, body)>
        <!ATTLIST html
          xmlns       %URI;          #FIXED 'http://www.w3.org/1999/xhtml'
        >

(see comments on querying XHTML below for the consequences of this).

The W3C provides a validator that checks the validity of HTML/XHTML documents and reports problems.
Here is an example XHTML document (that validated in early 2002).
HTML documents can be transformed (more or less ...) to XHTML by tidy html-filename > out-filename

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XPath

Parts of XPath are also supported by xmllint (see above).
XPath queries can be executed using several tools:

(as a subset of XQuery) using the XQuery/XSLT-Demo WebService (against publicly available XML instances); see below for XQuery, or
using saxonXQ (again, as a subset of XQuery, for more information, see next section).
Here, the document must be given explicitly by doc('filename'); it is possible to access either documents in the local filesystem or anywhere on the Web.
Example for usage of saxonXQ:
```
     saxonXQ "{doc('/afs/informatik.uni-goettingen.de/course/xml-lecture/Mondial/mondial.xml')//country/name}"
     saxonXQ "{doc('http://www.dbis.informatik.uni-goettingen.de/Mondial/mondial.xml')//country/name}"
```

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XQuery

W3C documents:

XQuery 3.0 (8.4.2014)
XPath and XQuery Operators and Functions 3.0 (8.4.2014)
General information about XQuery, amongst other things a list of implementations.

Used in this course:

The saxon lightweight tool:
The following aliases should be set in the file .bashrc:
```
alias saxonXQ='java -cp /afs/informatik.uni-goettingen.de/group/dbis/public/saxon/saxon9.jar net.sf.saxon.Query'
```
```
alias saxonXSL='java -cp /afs/informatik.uni-goettingen.de/group/dbis/public/saxon/saxon9.jar net.sf.saxon.Transform' 
```
Call saxonXQ filename.xq to execute an XQuery (or XPath query) from a file. The query in filename.xq must address a document by using the
doc('filename.xml or url') function.
Here, filename.xml is a name of a file in the local file system, saxonXQ also accepts urls for addressing documents from the web.
In order to call saxonXQ for a local file, additionally the option "-s" can be used:
```
saxonXQ -s:/afs/informatik.uni-goettingen.de/course/xml-lecture/Mondial/mondial.xml filename.xq
```
Thus, it is not necessary to specify the document in the query file. This can also be specified as an alias:
```
alias saxonXQMondial='saxonXQ -s:/afs/informatik.uni-goettingen.de/course/xml-lecture/Mondial/mondial.xml'
```
Command line for XQuery options (see here for complete list)
- !indent=yes (bash: \!indent=yes) for indented output
- -update:on for (saxonEE required)
Download: Download Saxon, unpack it, set CLASSPATH accordingly, set aliases for saxon-XQuery and saxon-XSL accordingly.
The XQuery/XSLT-Demo WebService. This WebService also uses Saxon internally.

The WebService is also available for local installations for Download and for copying in the CIP Pool at
/afs/informatik.uni-goettingen.de/course/xml-lecture/XML-Tools/xquery-demo.war
It can be used with any standard web application server, e.g. tomcat (see installation).

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XSLT Stylesheets

The main use for XSLT stylesheets is the transformation fom XML to XML or to HTML (see also below).

saxon (supports XSLT 2.0):
call saxonXSL xml-file stylesheet.xsl
In order to install it yourself: download Saxon, unpack it, set CLASSPATH accordingly, set aliases for saxon-XQuery and saxon-XSL accordingly.
The XQuery/XSLT-Demo WebService. This WebService also uses Saxon internally.
xalan (implements XPath/XSLT 1.0):
xalan -xsl stylesheet.xsl -in xml-input
xsltproc (belongs to the XSLT library for Gnome):
xsltproc stylesheet.xsl xml-input
xsltproc −−debug stylesheet.xsl xml-input produces a "sax-style" depth-first traversal of the input tree.

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Transformation Stylesheets

if a stylesheet is given in the document header, most browsers do not show the XML source, but directly apply the stylesheet and show the result:
mondial-with-stylesheet.xml is processed by mondial-simple.xsl that shows a table of the countries. If you execute "view page source" in your browser, you see the original XML file.
redirected-input.xsl is a stylesheet that gets its input from another file. Try this out by viewing dummy.xml in your browser: viewing this file starts redirected-input.xsl that in course states a query against mondial-europe.xml.
other example stylesheets can be found in /afs/informatik.uni-goettingen.de/course/xml-lecture/XSLT:
- orgs-and-members.xsl (XML to HTML)
- redirected-output.xsl (generates two new XML instances from one)

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XMLSchema

Example: mondial.xsd, can also be found here:

/afs/informatik.uni-goettingen.de/course/xml-lecture/Mondial/mondial.xsd

SQC (XML Schema Quality Checker) checks the quality of a schema (i.e. validates it against the XML Schema Specification) (i.e., it does not validate a document against an XML Schema).
- move to cd /afs/informatik.uni-goettingen.de/course/xml-lecture/XML-Tools/SQC and then call ./SQC.sh any-xsd-filename.xsd.
xmllint can be used for XML Schema validation:
xmllint -noout -schema <schemafilename> <file.xml>
Saxon EE supports XML Schema. Download evaluation license and saxon EE version from http://www.saxonica.com.
Call java -cp path-to-saxon9ee.jar com.saxonica.Validate -xsd:xsd-filename xml-filename.
```
java -cp ~dbis/XML-Tools/saxon/saxon9ee.jar com.saxonica.Validate -xsd:mondial.xsd mondial.xml
```

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SQL/XML under Oracle

SQL Web interface (in addition to the Mondial tables, the tables mondial, countryXML, cityXML used on the slides exist)
an online documentation can be found here.

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RDF/OWL

The W3C RDF Validator validates and visualizes RDF documents (given in RDF/XML format).
a collection of OWL ontologies

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Note: tomcat is not a full-fledged Web Server (like the Apache Web Server), but a Web Servlet Container with a simple Web Server. It does not host (plain HTML) Web pages, but Web Services. Tomcat can be run in an Apache Web Server to have both together. Here, we deal with tomcat only.

Students can install tomcat on their computers at home, and even install/run it in their accounts on the computers in the CIP Pool:

Download Apache tomcat here,
unpack it in your home directory (it will create a directory tomcatX-Y-Z/), rename the directory just to "tomcat" (or put a softlink by ln -s tomcatX-Y-Z tomcat),
first test:
cd tomcat/bin
./startup.sh
look into the logfile: tail -f ~/tomcat/logs/catalina.out
tomcat is now accessible on port 8080:
Browser: localhost:8080 should show an empty page (while e.g. localhost:8081 says "not found")
copy e.g. the XQuery/XSLT Demo Servlet (download) into tomcat's webapps directory:
cp /afs/informatik.uni-goettingen.de/course/xml-lecture/XML-Tools/xquery-demo.war tomcat/webapps/
cd tomcat/bin
./shutdown.sh don't forget this. Running tomcat twice crashes. If you forget it, down and up, until it works again.
./startup.sh will unpack the .war automatically.
Watch the logfile: tail -f ~/tomcat/logs/catalina.out
Browser: localhost:8080/xquery-demo ... and there it is!
Own servlets are not developped inside tomcat, but anywhere (e.g. using eclipse).
Go to your home directory (or wherever you maintain your source codes) and get the ServletDemo (download):
cp /afs/informatik.uni-goettingen.de/course/xml-lecture/servletdemo.zip .
unzip servletdemo.zip
cd servletdemo
there is an ant-file "build.xml" in it. (by the way, ant is written in XML, but now we just want to use it).
Set the CATALINA_HOME environment variable to your tomcat. You can do this by adding
export CATALINA_HOME="/home/YOURNAME/tomcat"
(note: a relative path ~/tomcat will NOT work)
to your .bashrc file, or simply (temporarily) by executing that command now.
Run the build.xml with the deploy target:
ant deploy and it copies its executable into tomcat/webapps.
cd tomcat/bin
./shutdown.sh
./startup.sh
Watch the logfile: tail -f ~/tomcat/logs/catalina.out
Browser: localhost:8080/servletdemo ... and there it is!
note: you did not even yet need to edit the configuration file in tomcat/conf/server.xml. If the servlet name is the same as the source code name in the webapps, it is found automatically.
For Web Service communication between different computers in the CIP Pool, Tomcats running on other computers in the CIP Pool can be addressed by cip0XX.cip.loc:8080.
You can also run two tomcats on the same computer by installing another one in a directory tomcat2/. Set the Connector port of the second one to 8081, and its shutdown port (by default set to 8005) to 8006 in its tomcat2/conf/server.xml.

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Playground page for the XML Course

Table of contents

XML Examples

Data-centric XML: The Mondial XML database

Text-oriented XML: Shakespeare's Plays

Mixed Text- and Database-oriented XML: DBIS publication list

XML Tools and Links

Browsing, editing

Validation, Navigation, Exploration

XHTML

XPath

XQuery

XSLT Stylesheets

Transformation Stylesheets

XMLSchema

SQL/XML under Oracle

RDF/OWL

Tomcat/Web Services