XML PowerPoint

View PowerPoint Presentation

XML as a Document Exchange Format
Tom Loukas
AMS Center for Advanced Technologies
September 26th, 2001

Why XML?

• To exchange data you must speak a common language
  
• XML is well on its way to becoming that language
  
  • Flexible self-describing language
    
  • Worldwide sanctioning bodies
    
  • Supported by most major software vendors
    
  • Already adopted by many industries

What is XML?

• Extensible Markup Language
  
• Structured language using tags to describe data elements with a document
  
• Designed to facilitate data exchange over the internet
  
• Version 1.0 of spec released in 1998 by World Wide Web Consortium (W3C)
  
• Many additions to spec since then

Some Design Goals for XML

• Straightforward use over the Internet
  
• Support a wide variety of applications
  
• Ease of programmatic processing
  
• XML documents should be human-legible and reasonably clear
  
• XML documents shall be easy to create

Sample XML Document

<purchaseOrder orderDate="1999-10-20">
<shipTo country="US">
<name>Alice Smith</name>
<street>123 Maple Street</street>
<city>Mill Valley</city>
<state>CA</state>
<zip>90952</zip>
</shipTo>
<items>
<item partNum="872-AA">
<productName>Lawnmower</productName>
<quantity>1</quantity>
<price>148.95</price>
</item>

Sample XML Document (continued)

<item partNum="926-AA">
<productName>Baby Monitor</productName>
<quantity>1</quantity>
<price>39.98</price>
<shipDate>1999-05-21</shipDate>
</item>
</items>
</purchaseOrder>
XML Document Definition - DTD
n Part of XML version 1.0
n Used to specify structure of an XML document
- Element names, element structure, attribute names, valid value lists
n Can be embedded within the XML document or specified via a location reference (e.g. a URL)
n Uses non-XML syntax and lacks ability to specify data types

Sample XML DTD

<!DOCTYPE purchaseOrder [
<!ELEMENT purchaseOrder (shipTo, Items) >
<!ATTLIST purchaseOrder orderDate CDATA #REQUIRED >
<!ELEMENT shipTo (name, street, city, state, zip) >
<!ATTLIST shipTo country CDATA #REQUIRED >
<!ELEMENT name (#PCDATA) >
<!ELEMENT street (#PCDATA) >
<!ELEMENT city (#PCDATA) >
<!ELEMENT state (#PCDATA) >
<!ELEMENT zip (#PCDATA) >
<!ELEMENT Items (item+) >
<!ELEMENT item (productName, quantity, USPrice) >
<!ATTLIST item partNum CDATA #REQUIRED >
<!ELEMENT productname (#PCDATA) >
<!ELEMENT quantity (#PCDATA) >
<!ELEMENT USPrice (#PCDATA) >

XML Document Definition - Schema

• Created to address failings of original DTD specification
  
• Support for data typing
  
• Enables more rigorous validation
  
• Uses XML syntax
  
• Finally became part of official spec in May 2001

Sample XML Schema

Sample XML Schema (continued)
Definition of the USAddress complex type

<xsd:complexType name="USAddress">
<xsd:sequence>
<xsd:element name="name" type="xsd:string"/>
<xsd:element name="street" type="xsd:string"/>
<xsd:element name="city" type="xsd:string"/>
<xsd:element name="state" type="xsd:string"/>
<xsd:element name="zip" type="xsd:decimal"/>
</xsd:sequence
<xsd:attribute name="country" type="xsd:NMTOKEN" fixed="US"/>
</xsd:complexType>

Sample XML Schema (continued)
Definition of the USAddress complex type

<xsd:complexType name="Items">
<xsd:sequence>
<xsd:element name="item" minOccurs="0"
maxOccurs="unbounded">
<xsd:complexType>
<xsd:sequence>
<xsd:element name="productName" type="xsd:string"/>
<xsd:element name="quantity">
<xsd:simpleType>
<xsd:restriction base="xsd:positiveInteger">
<xsd:maxExclusive value="100"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>

Sample XML Schema (continued)
…more child elements of the "item" element …..

<xsd:element name="USPrice" type="xsd:decimal"/>
<xsd:element name="shipDate" type="xsd:date"
minOccurs="0"/>
</xsd:sequence>
<xsd:attribute name="partNum" type="xsd:string" use="required"/>
</xsd:complexType
</xsd:element>
</xsd:sequence
</xsd:complexType>

Manipulating XML Documents

• Parsing
  
  • DOM (Document Object Model) Parsers
    
  • SAX (Simple API for XML) Parsers
    
• Translating
  
  • XSLT processors
    
  • XML Mapping tools
    
  • Custom code
    
• Editing
  
  • Text editors
    
  • Third party tools (e.g. XML Spy)
    
• Storage and retrieval
  
  • Store as large text or binary object in an RDBMS
    
  • Map XML elements to columns of relational tables
    
• Use specialized XML data store (e.g eXelon)

Major Uses of XML

• Data and document exchanges (A2A, B2B, G2B, G2G)
  
• As a metadata format
  
• XLANG for process definitions (Microsoft)
  
• XMI for metadata exchange
  
• Separating content from presentation
  
• Emerging Web Services Paradigm
  
  • Business functions accessible over the web via widely used protocols
  • Developing Standards
    
    • SOAP: Invoking web services
      
    • WSDL: Describing web services
      
    • Others: UDDI, WSFL, ….
      

Sample Web Service invocation using SOAP and HTTP

HTTP/1.1 200 OK.Content-Type: text/xml; charset="utf-8". Content-Length: nnnn.
<SOAP-ENV:Envelope.xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/". SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/"/>.
<SOAP-ENV:Body>.<m:GetLastTradePriceResponse xmlns:m="Some-URI">
<Price>34.5</Price>.</m:GetLastTradePriceResponse>.
</SOAP-ENV:Body>
</SOAP-ENV:Envelope>

Benefits of XML

• Industry support
  
• IBM, Microsoft, Oracle, …..
  
• Ariba, Commerceone, webMethods, ...
  
• SAP, Baan, Siebel, Peoplesoft, AMS, ….
  
• Human readable
  
• Self describing
  
• New elements can be added readily

The Other Side of the Coin

• Parsing overhead
  
• Tag data and text format result in increased network utilization

XML Standards and Initiatives

• XML specification itself - W3C
  
• Industry-specific XML vocabularies
  
• FpML Financial Products Markup Language
  
• Vendor driven XML standards
  
• cXML and xCBL
  
• Open standards initiatives
  
• ebXML
  
• Government XML initiatives
  
• xml.gov

• Document types
  
• Document structure and content
  
• Document processing flow and rules
  

Organization A	Transmit order	Organization B
	Acknowledge receipt of order
	Provide estimated ship date
	Acknowledge receipt of ship date info
	Indicate order shipped
	Acknowledge receipt of shipping confirmation
	Payment notification
	Acknowledge payment notification

Other processing considerations

• Transport protocols and security
  
• Error handling procedures
  

Standards Administration

Some things to consider:

• Who will participate in developing and maintaining the standards?
  
• Where will the standard specifications reside? (schemas, process definitions, etc)
  
• What process will be used for approval consensus?
  
• How will change requests be administered?
  
• Others …...