XML Schema Patterns for Databinding

W3C XML Schema Patterns for Databinding Paul Downey, BT Chair, XML Schema Patterns for Databinding Working Group XML 2006, December 5th 2006

XML Schema ?

Validation XML Schema Post XML Schema Schema Instance Validation Processor Infoset

Description XML Schema XML Sender Instance Receiver

Types xs:string xs:int XML tns:Address foo:PurchaseOrder

Databinding ?

Databinding Abstraction Model XML

Model • Java • Database • Annotated DOM • JSON • PHP serialisation • XML • Whatever

Why Describe ?

Duck Typing XML ?

Force Array <opt> { <name>value</name> name => ‘value’ </opt> } { <opt> name => [ <name>value1</name> ‘value1’, <name>value2</name> ‘value2’ </opt> ] }

Static Typing { int accountNo; long ammount; string name; }

What’s wrong with Databinding ?

“State of the Art” • reject valid XML Schema documents • reject valid XML instance documents • content of valid XML instance documents often unavailable in model

Impedance Mismatch >< OO

Circles, Triangles, Rectangles XML 2003 http://www.idealliance.org/papers/dx_xml03/papers/06-02-01/06-02-01.html

I ! Mixed Content text <O/> text <O> text </O>

Don’t Databind? • XSLT • DOM • LINQ • E4X • XJ • etc

Abstraction Scale Objects Infoset XML Bits Typed DOM Text DOM Templating

They Don’t Like XML!

Abstraction ?

XML Schema is Big .. • Lot’s of ways to describe the concrete • Lot’s of ways to represent the abstract

Partial Implementations “Our tool doesn’t support xs:foo. Change your schema.” * vendor

So begins .. “The Barf Dance”

it’s not so much that schema sucks ...

or that databinding tools suck ...

it’s that all databinding tools suck differently

W3C Working Group ?

WS-I • Basic Proﬁle • XML Schema Work Plan Working Group

W3C Workshop XML Schema 1.0 User Experiences

Discussion

Don’t Just Change Schema! … 300,000+ developers use XSD … There is tremendous value in XML Schema. Don't just change it… Soumitra Sengupta, Microsoft

Discussion Topics • versioning • proﬁles and patterns of use • code generation (v) validation • Unique Particle Attribution (UPA) • XML Schema 1.1 • test suite

W3C XML Schema Patterns for Databinding Working Group !

Deliverables • W3C Recommendation for Basic Patterns • W3C Recommendation for Advanced Patterns • Test Suite • Mechanism to Detect patterns

Out of Scope: • Proﬁle of Schema • Language Speciﬁc Detail

Patterns !

AnyURIElement .//xs:element/@type[resolve-QName(.,..) = xs:QName('xs:anyURI')] <xs:element name=\"anyURIElement\" type=\"xs:anyURI\" /> http://www.w3.org/2002/ws/databinding/patterns/6/09/AnyURIElement

ElementMinOccurs0 MaxOccursUnbounded .//xs:element[@minOccurs = '0' and @maxOccurs = 'unbounded']/ (@minOccurs, @maxOccurs) http://www.w3.org/2002/ws/databinding/patterns/6/09/ElementMinOccurs0MaxOccursUnbounded

SequenceSingle RepeatedElement .//xs:sequence[count(xs:element) = 1]/ xs:element[@maxOccurs = 'unbounded']/ (., @maxOccurs) Overlapping! http://www.w3.org/2002/ws/databinding/patterns/6/09/SequenceSingleRepeatedElement

StringEnumerationType .//xs:simpleType/xs:restriction[ @base/resolve-QName(.,..) = xs:QName('xs:string') and xs:enumeration]/ (., @base, xs:enumeration/(., @value)) <xs:simpleType name=\"Beatle\"> <xs:restriction base=\"xs:string\"> <xs:enumeration value=\"John\" /> <xs:enumeration value=\"Paul\" /> <xs:enumeration value=\"George\" /> <xs:enumeration value=\"Ringo\" /> </xs:restriction> http://www.w3.org/2002/ws/databinding/patterns/6/09/StringEnumerationType

SOAP Encoded Array ./xs:complexType[@name]/xs:complexContent/ xs:restriction[ @base/resolve-QName(.,..) = xs:QName ('soap11enc:Array')]/ xs:attribute[(@ref/resolve-QName(.,..) = xs:QName('soap11enc:arrayType')) and @wsdl11:arrayType]/ (../.., ../(., @base), ., @ref, @wsdl11:arrayType) http://www.w3.org/2002/ws/databinding/patterns/6/09/SOAPEncodedArray

Palatability ?

Value Judgement • xs:any becomes XMLElement • xs:anyURI becomes String • xs:decimal becomes String

Examples !

ElementMinOccurs0 MaxOccursUnbounded <xs:element name=\"durationList\" type=\"ex:DurationList\" /> <xs:complexType name=\"DurationList\"> <xs:sequence> <xs:element name=\"durationValue\" type=\"xs:short\" ! ! ! ! ! minOccurs=\"0\" maxOccurs=\"unbounded\" /> </xs:sequence> </xs:complexType> http://www.w3.org/2002/ws/databinding/examples/6/09/ElementMinOccurs0MaxOccursUnbounded

Example Descriptions • ComplexTypeSequenceExtension.xsd • echoComplexTypeSequenceExtension.xsd • echoComplexTypeSequenceExtension.wsdl • echoComplexTypeSequenceExtension-wsdl20.wsdl

Example Instances • ElementMinOccurs0MaxOccursUnbounded-01.xml • echoElementMinOccurs0MaxOccursUnbounded-01.xml • echoElementMinOccurs0MaxOccursUnbounded-01-soap11.xml • echoElementMinOccurs0MaxOccursUnbounded-01-soap12.xml

Test Suite Example Description Instance Model Toolkit Output

Test Reports

Patterns Detector !

Patterns Detector XML Patterns Schema Detector (URIs)

Buckets !

Basic Patterns • known to work with “state of the art” implementations • they’re, um, very Basic Publishers of Schemas Take Note!

TargetNamespace .[@targetNamespace]/ (., @targetNamespace) An [XML Schema 1.0] document conforming to this speciﬁcation MUST deﬁne a targetNamespace whose value is an absolute URI. † http://www.w3.org/2002/ws/databinding/patterns/6/09/TargetNamespace

“State of the Art” ?

SLIPPERY SLOPE

Value Judgement • new tools arrive • old tools become defunct • some tools are very lame • we can’t test every tool “Bring out your implementations”

Advanced Patterns • exhibited by real schemata • they’re, um, not very interoperable Developers of Implementations Take Note!

Not Advanced ?

SLIPPERY SLOPE

Value Judgement • XML Schema is big • Coverage or Possible to Databind? • always another Schema “Bring out your schemata”

Patterns in the Wild

Build Your Own Bucket • List Patterns your schemas use • List Patterns your toolkit supports • Analyse schemas “in the wild”

XML Schema Patterns for Databinding

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