XML as a Document Exchange Format

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International Business and Technology Consultants

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>

Element tags

Attributes

Data


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>

Element tags

Attributes

Data


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

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

<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">

<xsd:element name="purchaseOrder" type="PurchaseOrderType"/>

<xsd:complexType name="PurchaseOrderType">

<xsd:sequence>

<xsd:element name="shipTo" type="USAddress"/>

<xsd:element name="items" type="Items"/>

</xsd:sequence>

<xsd:attribute name="orderDate" type="xsd:date"/>

</xsd:complexType>


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>



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>



…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

POST /StockQuote HTTP/1.1Host: www.stockquoteserver.comContent-Type: text/xml; charset="utf-8"Content-Length: nnnnSOAPAction: "Some-URI"

<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:GetLastTradePrice xmlns:m="Some-URI"> <symbol>DIS</symbol> </m:GetLastTradePrice> </SOAP-ENV:Body> </SOAP-ENV:Envelope>


Sample Web Service response

HTTP/1.1 200 OKContent-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


Establishing XML standards for data exchange

Document types Document structure and content Document processing flow and rules


Document processing flow and rules

Organization A Organization B

Transmit order

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 …...


Thank you