1. XML Databases
by Sebastian Graf
Hier beginnt mein toller Vortrag

2. Table of Contents XML Database Overview XML Database Example XPath
XML-QL
XQuery
Storing of XML Databases
Relational DB vs. XML
XML based Systems
Hier sieht man gerade das Inhaltsverzeichnis. Echt jetzt.

3. XML Database Overview XML DB Navigation in Tree Tree structure
Think in nodes & axes
Navigation in Tree
XPath
Tree structure  contrast to SQL where relations are basic
Big difference between SQL & XML  SQL says what should be selected, but not how ( Oracle,DB2)
Very important in the navigation  XPath

4. XML Database Example <europe>
<country car_code = D memberships = org-eu org-nato …>
<name>Germany</name>
<capital>Berlin</capital>
<poulation> </population>
<country code>de</country code>
<bundesland>
<name>NRW</name>
<capital>Düsseldorf</captial>
<population> </population>
</bundesland>
</country>
</europe>
As every XML File, a XML Database has a root  europe
Elemets in country cannot have childs could also be written as childs  Design Feature
2 Capitals !!!  no problem because they are on different hirachy level

5. XPath Describes how to process XML items
logical path to a node (location path)
Provides abstraction for XML languages
XSLT
XPointer
XQuery
XPath is a language that describes a way to locate and process items in Extensible Markup Language
XSLT  Extensible Stylesheet Language Transformations
XPointer  XPointer is a language for locating data within a XML document based on properties such as location within the document, character content, and attribute values

6. XPath /europe/country/name Selects all names
With predecessor „country“
With predecessor „europe“
Addressing like in the Unix Filesystem
/europe/country/name selects all nodes „name“ that have a predecessor (father) country which has a father europe

7. XPath examples /europe/country[population > 50 000 000]
 All countries with population >
 All car_codes of Europe
/europe/country[name = Germany]//capital
 All captials in Germany

8. XPath Conclusion XPath offers basics navigation and selection features
However it is no complete XML Query Language
No joins possible

9. Table of Contents XML Database Overview XML Database Example XPath
XML-QL
XQuery
Storing of XML Databases
Relational DB vs. XML
XML based Systems

10. XML-QL Early proposal for XML Query language Structure:
<Selection part> <construction part>
WHERE #### IN #### CONSTRUCT ####
Result : XML Document
Selection Part : conditions for finding
Construction Part : way of creating an XML document
Structure : like SQL : select #### from #### where #### only the other way round

11. XML-QL Example
WHERE <country car_code=$id> <name>$name</> </> IN “…/europe.xml“ CONSTRUCT <country car_code=$id name=$name</>
<result> <country car_code=“D” name=“Germany”></> <country car_code=“F” name=“France”></> ….. </result>
$id und $name are bonded to the car_code attribute and the content of the name element
For every variable bounding a new country element ist created

12. XQuery XQuery should extend functionality of XML-QL
Design was related to SQL
XQueries are of the form : FOR ### LET ### WHERE ### RETURN ###  FLWR or Flower
Also possible: FOR-IN (FLWR) WHERE … (FLWR) … RETURN … (FLWR)…
Extended to XML-QL  joins are possible
Like XML-QL, Xquery returns a XML decument
The basic structure cann be enhanced by putting more variables into the FOR and LET parts
Where gives conditions  like in SQL
Return produces XML document
Nested queries are possible

13. XQuery example
Task : find all countires, that have a population > and have at least 10 cities
FOR $c IN document(„europe.xml“) // country
LET $cities := $c // city
WHERE > AND count($cities) > 10
RETURN <bigcountry population =
{$cities}
</bigcountry>
$c runs over all country elements.
For every „$c“ the variable $cities is connected to all cities of $c

14. XQuery Join example
Task : find all pairs of countires and cities, that have the same name
FOR $country IN //country, $city IN //city
WHERE $country/name/text() = $city/name/text()
RETURN <pair name={$country/name/text()}
This is a nested query

15. XQuery – what is missing?
No data manipulation in version 1.0
Raw Data has to be accessed for data manipulation
Planned for later versions:
Delete
Rename
Insert
Replace
What does this mean? Data can only be manipulated, by directly accessing the raw data

16. Table of Contents XML Database Overview XML Database Example XPath
XML-QL
XQuery
Storing of XML Databases
Relational DB vs. XML
XML based Systems

17. Storing of XML Databases
First Approach : one CLOB
Whole Database stored as value
Very easy to implement
SQL statements cannot be used for query
Second Approach : transformation
Transformation to Relations
SQL statements can be used
High transformation effort
Relational Databases!!
A Character Large OBject (CLOB) is a varying-length string, measured in bytes, that can be up to 2 gigabytes long. A CLOB is used to store large single-byte character set data such as documents. A CLOB is considered to be a character string.

18. Relational DB vs. XML The SilkRoute Xperanto
Automatic transformation : relations  XML
Predefined DTD
Xperanto
Mapping of relational Database to XML
Adds XML functionality to DB2

19. XML based Systems (B2B) Software AG eXcelon Tamino
XML platform
Storing
Development
Integreation
eXcelon
Query interface for XPath
Software AG  Tamino XML platform
Storing
Development
Integreation

20. More about XML databases
Web & Datenbanken
dpunkt.verlag
by Erhard Rahm & Gottfried Vossen
ISBN :
BA Library : INF G

21. Thanks for your attention
THE END
Thanks for your attention