IT420: Database Management and Organization XML 21 April 2006 Adina Crăiniceanu

Kroenke, Database Processing 2 Overview  From HTML to XML  DTDs  Transforming XML: XSLT

Kroenke, Database Processing 3 Introduction  Database processing and document processing need each other  Database processing needs document processing for transmitting/ expressing database views  Document processing needs database processing for storing and manipulating data  Internet expansion made the need obvious

Kroenke, Database Processing 4 XML  XML: Extensible Markup Language, developed in early 1990s  Hybrid of document processing and database processing  It provides a standardized yet customizable way to describe the content of documents  A recommendation from the W3C  XML = data + structure  XML generated by applications  XML consumed by applications  Easy access: across platforms, organizations

Kroenke, Database Processing 5 XML What is this? What does it mean? Madison HTML: How to display information on a browser. HTML: no “semantic” information, i.e. no meaning ascribed to tags

Kroenke, Database Processing 6 XML: Semantic information Madison Madison Madison, U of Wisc Madison, James (JMU)

Kroenke, Database Processing 7 XML vs. HTML  XML is better than HTML because It provides a clear separation between document  structure  content  materialization  It is standardized but allows for extension by developers  XML tags represent the semantics of their data

Kroenke, Database Processing 8 Why is XML important with regard to databases?  XML provides a standardized way to describe, validate, and materialize any database view.  Share information between disparate systems  Materialize data anyway you want  Display data on web  Display data on sales-person computer  Display data on mobile device

Kroenke, Database Processing 9 How does XML work? Three Primary Components to XML  Data has a structure  Document Type Declarations (DTDs)  XML Schemas can be used to describe the content of XML documents  Data has content  XML document  Data has materializations  Extensible Style Language: Transformations (XSLT)

Kroenke, Database Processing 10 If we want to share information is structure important?  Structure provides meaning …. What is the meaning of this bit stream?? The bit stream has meaning if we assign structure

Kroenke, Database Processing 11 Example: XML DTD & Document

Kroenke, Database Processing 12 XML DTD  XML document consists of two sections:  Document Type Declaration (DTD)  The DTD begins with DOCTYPE  Document data  XML documents could be  Type-valid if the document conforms to its DTD  Well-formed and not be type-valid, because  It violates the structure of its DTD  It has no DTD  DTD may be stored externally so many documents can be validated against the same DTD

Kroenke, Database Processing 13 Create XML Documents from Relational DB Data  Most RDBMS can output data in XML format  MySQL: mysql –u root --xml  For SQL Server:  SELECT... FOR XML RAW | AUTO, ELEMENTS | EXPLICIT

Kroenke, Database Processing 14 Lab exercise  Restore some database in MySQL  Open MySQL command line using  mysql –u root --xml

Kroenke, Database Processing 15 XSLT  XSLT, or the Extensible Style Language may be used to materialize (transform) XML documents using XSL document  From XML documents into HTML or into XML in another format  XSLT is a declarative transformation language  XSLT uses stylesheets to indicate how to transform the elements of the XML document into another format

Kroenke, Database Processing 16 Example: External DTD

Kroenke, Database Processing 17 Example: XML Document

Kroenke, Database Processing 18 Example: XML Document Michelle Correlli 1824 East 7th Avenue Suite 700 Memphis TN Lynda Jaynes 2 Elm Street New York City NY

Kroenke, Database Processing 19 XSL Stylesheet for CustomerList

Kroenke, Database Processing 20 Example: XML  Browser

Kroenke, Database Processing 21 Show XSL document example CustomerList.xml

Kroenke, Database Processing 22 XML Review  STRUCTURE: DTD or XML Schema  CONTENT: XML document  MATERIALIZATIONS: XSL document

Kroenke, Database Processing 23 Sharing Data: Transparency XML data XSL Trans Validate DTD Database Raw data Validate DTD XSL Trans XML data Database Raw data Business A Business B Agreed upon structure SHARE

Kroenke, Database Processing 24 Example XML Industry Standards  Accounting  Extensible Financial Reporting Markup Language (XFRML)  Architecture and Construction  Architecture, Engineering, and Construction XML (aecXML)  Automotive  Automotive Industry Action Group (AIAG)  XML for the Automotive Industry (SAE J2008)  Banking  Banking Industry Technology Secretariat (BITS)  Bank Internet Payment System (BIPS)  Electronic Data Interchange  Data Interchange Standards Association (DISA)  XML/EDI Group

Kroenke, Database Processing 25 What About XML Queries?  Xpath  A single-document language for “path expressions”  Not unlike regular expressions on tags  E.g. /Contract/*/UnitPrice, /Contract//UnitPrice, etc.  XSLT  XPath plus a language for formatting output  XQuery

Kroenke, Database Processing 26 Conclusions  XML: The new universal data exchange format  Unlike HTML, XML = data + semantics  STRUCTURE: DTD or XML Schema  CONTENT: XML document  MATERIALIZATIONS: XSL document  More flexible than relational model  More difficult to query – research