XML as a Document Exchange Format

1
XML as a Document Exchange Format

• Tom Loukas
• AMS Center for Advanced Technologies
• September 26th, 2001

2
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

3
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

4
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

5
Sample XML Document

• ltpurchaseOrder orderDate"1999-10-20"gt
• ltshipTo country"US"gt
• ltnamegtAlice Smithlt/namegt
• ltstreetgt123 Maple Streetlt/streetgt
• ltcitygtMill Valleylt/citygt
• ltstategtCAlt/stategt
• ltzipgt90952lt/zipgt
• lt/shipTogt
• ltitemsgt
• ltitem partNum"872-AA"gt
  
• ltproductNamegtLawnmowerlt/productNamegt
• ltquantitygt1lt/quantitygt
• ltpricegt148.95lt/pricegt
• lt/itemgt

Element tags Attributes Data
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Sample XML Document (continued)

• ltitem partNum"926-AA"gt
• ltproductNamegtBaby Monitorlt/productName
  gt
• ltquantitygt1lt/quantitygt
• ltpricegt39.98lt/pricegt
• ltshipDategt1999-05-21lt/shipDategt
• lt/itemgt
• lt/itemsgt
• lt/purchaseOrdergt

Element tags Attributes Data
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XML Document Definition - DTD

• Part of XML version 1.0
• Used to specify structure of an XML document
• Element names, element structure, attribute
  names, valid value lists
• Can be embedded within the XML document or
  specified via a location reference (e.g. a URL)
• Uses non-XML syntax and lacks ability to specify
  data types

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Sample XML DTD

• lt!DOCTYPE purchaseOrder
• lt!ELEMENT purchaseOrder (shipTo, Items) gt
• lt!ATTLIST purchaseOrder orderDate CDATA REQUIRED
  gt
• lt!ELEMENT shipTo (name, street, city, state, zip)
  gt
• lt!ATTLIST shipTo country CDATA REQUIRED gt
• lt!ELEMENT name (PCDATA) gt
• lt!ELEMENT street (PCDATA) gt
• lt!ELEMENT city (PCDATA) gt
• lt!ELEMENT state (PCDATA) gt
• lt!ELEMENT zip (PCDATA) gt
• lt!ELEMENT Items (item) gt
• lt!ELEMENT item (productName, quantity, USPrice) gt
• lt!ATTLIST item partNum CDATA REQUIRED gt
• lt!ELEMENT productname (PCDATA) gt
• lt!ELEMENT quantity (PCDATA) gt
• lt!ELEMENT USPrice (PCDATA) gt

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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

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Sample XML Schema

• ltxsdschema xmlnsxsd"http//www.w3.org/2001/XMLS
  chema"gt
• ltxsdelement name"purchaseOrder"
  type"PurchaseOrderType"/gt
• ltxsdcomplexType name"PurchaseOrderType"gt
• ltxsdsequencegt
• ltxsdelement name"shipTo"
  type"USAddress"/gt
• ltxsdelement name"items"
  type"Items"/gt
• lt/xsdsequencegt
• ltxsdattribute name"orderDate"
  type"xsddate"/gt
• lt/xsdcomplexTypegt

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Sample XML Schema (continued)

• Definition of the USAddress complex type
• ltxsdcomplexType name"USAddress"gt
• ltxsdsequencegt
• ltxsdelement name"name"
  type"xsdstring"/gt
• ltxsdelement name"street"
  type"xsdstring"/gt
• ltxsdelement name"city"
  type"xsdstring"/gt
• ltxsdelement name"state"
  type"xsdstring"/gt
• ltxsdelement name"zip"
  type"xsddecimal"/gt
• lt/xsdsequence
• ltxsdattribute name"country"
  type"xsdNMTOKEN fixed"US"/gt
• lt/xsdcomplexTypegt

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Sample XML Schema (continued)

• Definition of the USAddress complex type
• ltxsdcomplexType name"Items"gt
• ltxsdsequencegt
• ltxsdelement name"item" minOccurs"0
• maxOccurs"unbounded"gt
• ltxsdcomplexTypegt
• ltxsdsequencegt
• ltxsdelement
  name"productName" type"xsdstring"/gt
• ltxsdelement
  name"quantity"gt
• ltxsdsimpleTypegt
• ltxsdrestriction
  base"xsdpositiveInteger"gt
• ltxsdmaxExclusive
  value"100"/gt
• lt/xsdrestrictiongt
• lt/xsdsimpleTypegt
• lt/xsdelementgt

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Sample XML Schema (continued)

• more child elements of the item
  element ..
• ltxsdelement name"USPrice"
  type"xsddecimal"/gt
• ltxsdelement name"shipDate"
  type"xsddate"
• minOccurs"0"/gt
• lt/xsdsequencegt
• ltxsdattribute name"partNum"
  type"xsdstring use"required"/gt
• lt/xsdcomplexType
• lt/xsdelementgt
• lt/xsdsequence
• lt/xsdcomplexTypegt

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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)

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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, .

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Sample Web Service invocation using SOAP and HTTP
POST /StockQuote HTTP/1.1Host
www.stockquoteserver.comContent-Type text/xml
charset"utf-8"Content-Length nnnnSOAPAction
"Some-URI"ltSOAP-ENVEnvelope
xmlnsSOAP-ENV"http//schemas.xmlsoap.org/soap/en
velope/" SOAP-ENVencodingStyle"http//schema
s.xmlsoap.org/soap/encoding/"gt
ltSOAP-ENVBodygt ltmGetLastTradePrice
xmlnsm"Some-URI"gt
ltsymbolgtDISlt/symbolgt lt/mGetLastTradePric
egt lt/SOAP-ENVBodygt lt/SOAP-ENVEnvelopegt
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Sample Web Service response
HTTP/1.1 200 OKContent-Type text/xml
charset"utf-8"Content-Length
nnnnltSOAP-ENVEnvelope xmlnsSOAP-ENV"http/
/schemas.xmlsoap.org/soap/envelope/"
SOAP-ENVencodingStyle"http//schemas.xmlsoap.org
/soap/encoding/"/gt ltSOAP-ENVBodygt
ltmGetLastTradePriceResponse xmlnsm"Some-URI"gt
ltPricegt34.5lt/Pricegt
lt/mGetLastTradePriceResponsegt
lt/SOAP-ENVBodygtlt/SOAP-ENVEnvelopegt
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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

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The Other Side of the Coin

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

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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

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Establishing XML standards for data exchange

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

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Document processing flow and rules
Transmit order
Organization A
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
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Other processing considerations

• Transport protocols and security
• Error handling procedures

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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 ...

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Thank you