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 Examples

The small "books" example (books.xml, books.dtd) of the lecture is available in the directory

/afs/informatik.uni-goettingen.de/course/xml-lecture/XML-DTD

Data-centric XML: The Mondial XML database

In the course, a nested XML version of the Mondial database is used.

XML instance "mondial.xml"
- excerpt: europe "mondial-europe.xml"
DTD "mondial.dtd"
XML Schema "mondial.xsd"

You find also all Mondial XML files in the directory /afs/informatik.uni-goettingen.de/course/xml-lecture/Mondial

Text-oriented XML: Shakespeare's Plays

A more text-oriented example uses Shakespeare's plays by John Bosak.
The files (XML and DTD) are installed at /afs/informatik.uni-goettingen.de/course/xml-lecture/Shakespeare/ .

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

The following files are available in the directory

/afs/informatik.uni-goettingen.de/course/xml-lecture/XML-DTD

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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 Unicode.
  - 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 -qs:. -s:filename.xml.

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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 saxon (the technical details for saxon are described below):
```
     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)

Used in this course:

The saxon lightweight tool:
- Usage of the installed saxon stuff in the IFI CIP pool:
  - set the following aliases in the file .bashrc:
```
  export $DBISPATH=/afs/informatik.uni-goettingen.de/user/d/dbisuser/XML-Tools
  export SAXON11CLASSPATH=$DBISPATH/saxon/saxon-he-11.4.jar:$DBISPATH/XMLResolver/xmlresolver-4.5.1.jar:$DBISPATH/XMLResolver/xmlresolver-4.5.1-data.jar
  alias saxonXQ='java -cp $SAXON11CLASSPATH net.sf.saxon.Query'
  alias saxonXSL='java -cp $SAXON11CLASSPATH net.sf.saxon.Transform'
  alias saxonValid='java -cp $SAXON11CLASSPATH net.sf.saxon.Query -qs:. -dtd:on '
```
  - Call saxonValid -s:filename.xml for validating an XML file that contains a DTD reference.
  - 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 XML source 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'
```
  - Further command line for XQuery options (see here for complete list)
    - !indent=yes (bash: \!indent=yes) for indented output
    - -update:on for (saxonEE required)
- Download Saxon
  - Download Saxon, unpack it.
  - it contains a saxon-he-x.y.z.jar. This is the main jar.
  - For resolving entities, URI DTD references (e.g., the W3C XHTML DTDs that are actually not accessible under their DTD URIs, see course slides for details), a Resolver is needed. This may be also useful for other XML applications.
    - The unzipped downloaded saxon package created a lib directory just beneath its jar, which contains:
      - xmlresolver-v.w.x.jar: the jar containing the resolver itself
      - xmlresolver-data-v.w.x.jar: supporting data, e.g. the W3C XHTML DTDs
    - alternatively, you can download the current version from the XMLResolver project.
  - set your CLASSPATH accordingly, set aliases for saxon-XQuery and saxon-XSL accordingly as described above.
- 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) (the technical details for saxon are described above):
  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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Tomcat/Web Services
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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Table of contents

Data-centric XML: The Mondial XML database

Text-oriented XML: Shakespeare's Plays

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

Browsing, editing

Validation, Navigation, Exploration

Transformation Stylesheets