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

Schema

Processor

XML

Instance

XML

Schema

Post

Schema

Validation

Infoset

Description

SenderXML

Instance

XML

Schema

Receiver

Types

XML

xs:string

xs:int

foo:PurchaseOrder

tns:Address

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></opt>

<opt> <name>value1</name> <name>value2</name></opt>

{ name => ‘value’}

{ name => [ ‘value1’, ‘value2’ ]}

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

XML

Text

InfosetObjects

DOMTypedDOM

Bits

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

“The Barf Dance”

So begins ..

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 WorkshopXML 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')]

http://www.w3.org/2002/ws/databinding/patterns/6/09/AnyURIElement

<xs:element name="anyURIElement"

type="xs:anyURI" />

ElementMinOccurs0MaxOccursUnbounded

.//xs:element[@minOccurs = '0' and @maxOccurs = 'unbounded']/ (@minOccurs, @maxOccurs)

http://www.w3.org/2002/ws/databinding/patterns/6/09/ElementMinOccurs0MaxOccursUnbounded

SequenceSingleRepeatedElement

.//xs:sequence[count(xs:element) = 1]/ xs:element[@maxOccurs = 'unbounded']/ (., @maxOccurs)

http://www.w3.org/2002/ws/databinding/patterns/6/09/SequenceSingleRepeatedElement

Overlapping!

StringEnumerationType

.//xs:simpleType/xs:restriction[ @base/resolve-QName(.,..) = xs:QName('xs:string') and xs:enumeration]/ (., @base, xs:enumeration/(., @value))

http://www.w3.org/2002/ws/databinding/patterns/6/09/StringEnumerationType

<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>

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

!

ElementMinOccurs0MaxOccursUnbounded

<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

Toolkit

Output

Example

Description

Instance

Model

Test Reports

Patterns Detector

!

Patterns Detector

DetectorPatterns

(URIs)XML

Schema

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)

http://www.w3.org/2002/ws/databinding/patterns/6/09/TargetNamespace

An [XML Schema 1.0] document conforming to this

specification MUST define a targetNamespace whose

value is an absolute URI. †

“State of the Art”

?

SLIPPERY SLOPE

Value Judgement

“Bring out your implementations”

• new tools arrive

• old tools become defunct

• some tools are very lame

• we can’t test every tool

Advanced Patterns

• exhibited by real schemata

• they’re, um, not very interoperable

Developers of Implementations Take Note!

Not Advanced

?

SLIPPERY SLOPE

Value Judgement

“Bring out your schemata”

• XML Schema is big

• Coverage or Possible to Databind?

• always another Schema

Patterns in the Wild

Build Your Own Bucket

• List Patterns your schemas use

• List Patterns your toolkit supports

• Analyse schemas “in the wild”

Other Topics

?

DocumentConformance

ImplementationConformance

WS-I Basic Profile

• Detector works on WSDL 1.1

• Composable with Basic Profile 1.1

Annotations

• Tools Generate them

• Useful for “round tripping”

• No-one is submitting them

Versioning

• Concrete patterns exist

• They’re all Advanced

XML Schema 1.1 is the answer?

Progress

?

Schedule

Participants

• BT

• Health Level 7

• National Association of Convenience Stores (NACS)

• Origo Services Limited

• SAP AG

• WSO2

• Invited Expert: Priscilla Walmsley

... and that’s It!

We Need Your Help!

www.w3.org/2002/ws/databinding

How You Can Help

• Participate in the Working Group

• Encourage your vendor of choice to participate

• Contribute to the test suite

• Contribute your Schemata

www.w3.org/2002/ws/databinding

Thank you! Any Questions

?www.w3.org/2002/ws/databinding