1. XML and Databases H.E. Erbs Übersicht Contents: Overview What is XML? Mapping rules - A simple classA simple class - Association of low multiplicityAssociation of low multiplicity - Association of high multiplicityAssociation of high multiplicity - HierachyHierachy Intermediate conclusion XML as a bridge - Exporting from MS-AccessExporting from MS-Access - Importing into FastObjectsImporting into FastObjects The XML reality

2. XML and Databases H.E. Erbs Übersicht XML model XML Database XML: Just an additional path in the data modelling flow chart?

3. XML and Databases H.E. Erbs Übersicht Each XML document (a database?) … is a (long) string (stored in a text file) consists of a header (conc. XML version and character set) (if necessary:) a reference to a structure definition file data (= a mixture of tags and content) Content and all tags (!) can be defined by the user. Structure information can be generated automatically on the basis of the XML documents. (-> first: create data and second: generate the structure)

4. XML and Databases H.E. Erbs Übersicht indicating many; at least one 106222 Kanne 1.20 59.00 1 106222.IMG … <!ELEMENT Produkt (Nummer, Bezeichnung, Groesse, Fassungsvermoegen, Preis, Funktion, Foto)> … … Mapping of a simple class This is the begin tag of an object and here is the corresponding end tag An object The corresponding document type definition (DTD) (a class definition) A set of objects

5. XML and Databases H.E. Erbs Übersicht Mapping of an association of low multiplicity <!ELEMENT Produkt (Nummer, Bezeichnung, Groesse, Fassungsvermoegen, Preis, Funktion, Foto)> Mapping multiplicity 0..*

6. XML and Databases H.E. Erbs Übersicht <xs:element ref="Produkt" minOccurs="0" maxOccurs="unbounded"/> … XML Schema: just another DDL Again: mapping multiplicity 0..*

7. XML and Databases H.E. Erbs Übersicht Mapping of an association of high multiplicity

8. XML and Databases H.E. Erbs Übersicht Krefelder Töpfermarkt … Lichtenberger Adventsmarkt … 106222 … 101222 … 10 20

9. XML and Databases H.E. Erbs Übersicht <!ELEMENT Markt (Bezeichnung, Standort, Oeffnungszeiten, Termin, URL)> <!ATTLIST WirdAngebotenAuf Produkt-Nr IDREF #REQUIRED Markt-Nr IDREF #REQUIRED >

10. XML and Databases H.E. Erbs Übersicht … … <xsl:apply-templates select="/MaerkteUndProdukte/M-P/WirdAngebotenAuf [@Markt-Nr=$MarktRef] "/> … <xsl:apply-templates select="/MaerkteUndProdukte/Produkte/Produkt [@Nr=$ProduktRef] "/> An XSL transformation using an XSLT style sheet

11. XML and Databases H.E. Erbs Übersicht And here is the result (displayed by OPERA browser)

12. XML and Databases H.E. Erbs Übersicht Mapping of a hierachy

13. XML and Databases H.E. Erbs Übersicht Meier Paula 4713 1.1.2002 A client (Kunde) element based on this DTD is as follows: Remark: This mapping rule differs from the corresponding one in The Book.

14. XML and Databases H.E. Erbs Übersicht Whos gonna use these concepts? Nobody. Nowadays data is stored in network or relational databases, but isnt stored in XML databases/documents. So, whats left (for XML)?

15. XML and Databases H.E. Erbs Übersicht XML as a bridge between heterogeneous databases [so-called Message-oriented middleware (MOM) architecture]

16. XML and Databases H.E. Erbs Übersicht Exporting a simple relation as part of an MS-Access database

17. XML and Databases H.E. Erbs Übersicht Importing an XML document into a FastObjects database (screen shot)

18. XML and Databases H.E. Erbs Übersicht Conclusions: 1.The XML path is just another path in data modelling, but it is of no importance in industry. Native XML database systems wont have a commercial future. 2.Import/export of data will be done on an XML basis. All database systems (will) offer interfaces for that basis.

19. XML and Databases H.E. Erbs Übersicht XML- DB XML document Reality Relational Database (e.g. Access) Object- oriented Database (e.g. POET) Network Database (e.g. UDS) The XML reality XML data model