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WS-I BP1.0 Recommendations On WSDL1.1. Kevin Liu October 2003. Objectives. Provide background information for Issue 72 What’s value of BP1.0 wrt BP1.0 BP1.0 constraints on use of WSDL1.1 BP1.0 clarifications on use of WSDL1.1 Conformance to BP1.0 Impacts on BPEL - discussion. What

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Presentation Transcript
objectives
Objectives
  • Provide background information for Issue 72
    • What’s value of BP1.0 wrt BP1.0
    • BP1.0 constraints on use of WSDL1.1
    • BP1.0 clarifications on use of WSDL1.1
    • Conformance to BP1.0
    • Impacts on BPEL - discussion
background wsdl1 1 basics
What

A portType describes the abstract interface of the Web service

Each contained operation can have an input, an output and a number of faultmessages

Background: WSDL1.1 Basics

part

*

message

*

0..1

0..1

fault

output

input

*

*

*

portType

operation

*

  • How
    • A binding specifies exactly one protocol for the operations of a portType

*

1

*

binding

1

  • Where
    • A port defines the Web service endpoint by specifying a single network address

*

service

port

*

background wsdl 1 1 a simplified example

XML Schema

What

how

Where

Background: WSDL 1.1 – A simplifiedExample

<definitions name="StockQuote“ …>

<types>

<schema ...> <complexType name="TimePeriod">

<element name="startTime"type="xsd:timeInstant"/> ...

</complexType> </schema>

</types>

<message name="GetTradePricesInput">

<part name="tickerSymbol" type="xsd:string"/> ...

</message>...

<portType name="StockQuotePortType">

<operation name="GetLastTradePrice">

<input message="tns:GetTradePricesInput"/><output message="tns:GetTradePricesOutput"/>

</operation>

</portType>

<binding name="StockQuoteSoapBinding" type="tns:StockQuotePortType">

<soap:binding style="rpc" transport="http://schemas.xmlsoap.org/soap/http"/>

<operation name="GetTradePrices"> <soap:operation soapAction="..."/>

<input> <soap:body use="encoded" ... encodingStyle="..."/></input> ...

</operation>

</binding>

<service name="StockQuoteService">

<port name="StockQuotePort" binding="tns:StockQuoteBinding">

<soap:address location="http://example.com/stockquote"/>

</port>

</service>

</definitions>

what s the value of bp1 0 wrt wsdl1 1
What’s the value of BP1.0 wrt WSDL1.1?
  • BP1.0 aims at interoperability
    • It’s the result of resolving 344 interoperability issues reported by 100+ WS-I members
    • It provides 161 recommendations about using its selected specifications, majority focuses on the use of WSDL1.1
  • WSDL1.1 contains many errors, ambiguities, and inconsistencies (among the spec text, examples, and schemas)
    • BP1.0 provides clarifications, correction, examples and guidance to improve the usability and interoperability of WSDL1.1
  • WSDL1.1 allows multiple mechanisms to do same thing while many of the mechanisms are underspecified and causes interoperability problems. BP1.0 recommends the mostly adopted mechanism
    • XML schema as type system + soap over http as binding
  • BP1.0 contains 72 recommendations on WSDL1.1 (details to follow)
    • Constraints
    • Guidance
bp1 0 constraints on web services description
BP1.0 Constraints on Web services description
  • BP1.0 assigns WSDL1.1 as one of the mandatory mechanisms for describing a Web Service
    • A service must be described using WSDL, UDDI, or both
  • BP1.0 constraints on use of WSDL1.1
    • XML1.0 is mandated for WSDL definitions
    • XML schema is the only conformant type system
    • SOAP over HTTP is the only conformant binding
    • Disallow operation overloading - operation name must be unique within a portType
    • Disallow out-bound operations
    • Disallows (soap) encoding
      • No @use=“encoded” in wsdl bindings
      • No @encodingStyle in soap messages
bp1 0 clarifications on wsdl1 1
BP1.0 Clarifications on WSDL1.1
  • BP1.0 provides clarifications and guidance on the use of the following WSDL1.1 (details to follow)
    • Dedicated schema files
    • Ordering of top WSDL1.1 elements
    • wsdl:import vs. xsd:import
    • wsdl:[email protected] vs. @element
    • XML namespaces
    • Faults description
    • Use of RPC style
which wsdl1 1 schema files to use
Which WSDL1.1 schema files to use?
  • WSDL1.1 schemas in the appendix of the spec is out of date, and inconsistent with the spec in many cases
  • Earlier experimental projects have provided updates to the schemas. WS-I has made a snapshot of the updated schemas available in the following URIs
    • WSDL schema:
      • http://schemas.xmlsoap.org/wsdl/2003-02-11.xsd
      • Note this schema allows extension to portType
    • SOAP Binding schema:
      • http://schemas.xmlsoap.org/wsdl/soap/2003-02-11.xsd
  • A WSDL1.1 definition must be valid with the above schemas to claim BP1.0 conformant
  • Who is responsible for validating WSDL1.1 definition against the above schemas?
    • It’s the responsibility of the WSDL author to assure it’s schema validated
    • Consumers of the WSDL may be more tolerant if they choose to
order of wsdl elements
Order of WSDL elements
  • WSDL1.1 spec and its appended WSDL1.1 schema are inconsistent about what are the appropriate order of the top WSDL1.1 elements
  • BP1.0 provides the following guidance:
    • If present, the wsdl:import element must precede all other wsdl elements except wsdl:documentation
    • If present, wsdl:type must precede all other elements except wsdl:documentation and wsdl:import
    • The order of all other elements are not important, but in general it should be in the following order
      • documentation
      • import
      • types
      • message
      • portType
      • binding
      • service
wsdl import vs xsd import
wsdl:import vs. xsd:import
  • WSDL1.1 uses import mechanism to allow flexible authoring
    • Different sections of a WSDL definition can be defined in separate files and then imported into another WSDL file
    • wsdl:import is modeled after xsd:import, but the WSDL1.1 spec doesn’t provide any explanation about how it should be used
      • It’s interpreted differently by different vendor and causes interoperability problems
  • BP1.0 provides the following guidance:
    • wsdl:import can only be used to import other wsdl files
      • The imported definition can either in the same namespace, or in a different namespace than the importing definition
      • Namespace coercion is disallowed. The imported wsdl must be referenced with the same namespace as defined by its targetNamespace
      • The location attribute is required and so must not be empty, but its value should only be treated as a hint to the wsdl processor
    • xsd:import can only be used to import XML schema definitions
      • It can only be used in the <types> section
      • It should follow the same rules as specified in xml schema
example wsdl import vs xsd import
Example – wsdl:import vs xsd:import

<definitions ... xmlns:wsdl =“http://schemas.xmlsoap.org/wsdl/”

xmlns:test1 = “http://example.com/stockquote/test1”

xmlns:test2 = “http://example.com/stockquote/test2”>

<wsdl:import namespace=“http://example.com/stockquote/test1” location="http://example.com/stockquote/stockquote.wsdl"/>

<wsdl:types>

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

<xsd:import namespace=“http://example.com/stockquote/test2” schemaLocation="http://example.com/stockquote/stockquote.xsd"/>

</xsd:schema>

</wsd:types>

</definitions>

wsdl part@element vs wsdl part@type
wsdl:[email protected] vs. wsdl:[email protected]
  • WSDL:part has two exclusive attributes – element or type
    • One can use the “element” attribute to reference an XSD global element. e.g.

<message name="GetTradePricesInput"><part name=“purchaseOrder" element=“tns:purchaseOrder"/> ...

</message>

    • Or use “type” to reference an XSD simple or complex type. E.g. <message name="GetTradePricesInput"><part name="tickerSymbol" type="xsd:string"/> ...

</message>

    • The choice of “type” vs “element” has significant impact on soap binding definition, and in turn on the soap message
how to handle fault
How to handle fault?
  • Do you have to specify all faults in your WSDL? NO
    • A WSDL should, but not required to, include all known faults
    • Soap faults can appear as body fault or header fault
  • What is the “style” of soapbind:fault or soapbind:headerfault?
    • “RPC” is only appliable to soapbind:body
    • Headers, headerfaults, and faults are always “document” style
    • They can only refer to a wsdl:part that has been defined using the “element” attribute
  • What are the right fault code to use?
    • “VersionMismatch”, and “MustUnderstand” should be first checked
    • If the recipient receives a soap message that is inconsistent with its WSDL, it should generate a soap:Fault with a fault code of “Client”
use of xml namespaces
Use of xml namespaces
  • <xsd:schema> contained in the <wsdl:types> must have a target namespace attribute with a valid and non-null value
    • One exception: when xsd:import is its only child
  • The targetNamespace of a WSDL definition and the targetNamespace of its contained schema maybe the same – they are in different symbol spaces
use of rpc style
Use of RPC style
  • Many of BP1.0 recommendations are related to the use of RPC style
    • Already covered some in the slides for [email protected] use and namespace use
    • Example follows
example a rpc style wsdl1 1 definition
Example - A RPC style WSDL1.1 definition

In the case of RPC, the resulting soap message is described as a mix of wsdl constructs and xsd constructs.

  • <definitions … targetNamespace=“http://example.org/bar/” xmlns:foo=“http://example.org/foo/” xmlns:bar=“http://example.org/bar/” >
  • <types>
  • <xsd:schema targetNamespace="http://example.org/foo/" xmlns:tns="http://example.org/foo/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" elementFormDefault="qualified“ attributeFormDefault="unqualified">
      • <xsd:complexType name="fooType">
      • <xsd:sequence>
      • <xsd:element ref="tns:bar"/>
      • <xsd:element ref="tns:baf"/>
      • </xsd:sequence>
      • </xsd:complexType>
      • <xsd:element name="bar" type="xsd:string"/>
      • <xsd:element name="baf" type="xsd:integer"/>
  • </xsd:schema>
  • </types>
  • <message name="BarMsg">
  • <part name="BarAccessor" type="foo:fooType"/>
  • </message>
  • <portType name="BarPortType">
  • <operation name="BarOperation">
  • <input message="bar:BarMsg"/>
  • </operation>
  • </portType>
  • <binding name="BarSOAPBinding" type="bar:BarPortType">
  • <soapbind:binding transport="http://schemas.xmlsoap.org/soap/http/" style="rpc"/>
  • <operation name="BarOperation">
  • <input message="bar:BarMsg">
  • <soapbind:body use="literal" namespace="http://example.org/bar/"/>
  • </input>
  • </operation>
  • </binding>

used as the definition of part accessor children

used as the name of the part accessor

used as the name of the operation wrapper

used as the namespace of the operation wrapper

example the resulting soap message
Example – the resulting soap message
  • <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:foo="http://example.org/foo/">
  • <s:Header/>
  • <s:Body> <m:BarOperation xmlns:m="http://example.org/bar/"> <BarAccessor> <foo:bar>String</foo:bar> <foo:baf>0</foo:baf> </BarAccessor> </m:BarOperation>
  • </s:Body>
  • </s:Envelope>

Operation wrapper has the same name of the wsdl:operation, and it takes the ns value from soapbind:[email protected] in its wsdl definition

Children of part accessor have their namespace from their schema definition

Part accessor has the same name as the wsdl:[email protected], and it must not have any namespace

conformance to bp1 0
Conformance to BP1.0
  • BP1.0 has a well-defined scope which is decided by its underlying specifications.
    • Conformance is only relevant within its
    • BP1.0 covers WSDL1.1, SOAP1.1, UDDI 2.0 and a few other related specs
  • BP1.0 conformance is based on three kinds of artifacts
    • MESSAGE – the soap message
    • DESCRIPTION – the wsdl definition
    • REGDATA – the uddi registry elements
    • A conformant artifact has to meet all requirements targeted for that artifact
  • For DESCRIPTION, conformance can be claimed for the following elements of WSDL1.1
    • Port
    • Binding
    • portType
      • Operation
      • Message
  • Conformance is not about the overall WSDL definition. e.g. A WSDL definition may contain a conformant binding and multiple non-conformant bindings
how can i claim conformance to bp1 0
How can I claim conformance to BP1.0?
  • WS-I provides testing tools which can be used to check conformance of a target artifact, such as a SOAP message
  • WS-I defines a schema for wsi:Claim element which can be used to advertise conformance to a profile in different ways
    • WSDL top elements( e.g. wsdl:port, wsdl:binding, etc)
    • SOAP message header
    • UDDI tModel
  • For Example,

<wsdl:service name="MyService" >

        • <wsdl:port name="MyPort" binding="tns:MyBinding" >
        • <wsdl:documentation>
        • <wsi:Claim conformsTo="http://ws-i.org/profiles/basic/1.0" /> </wsdl:documentation>
        • <soapbind:address location="http://example.org/myservice/myport" />
        • </wsdl:port>

</wsdl:service>

discussion bp1 0 impact on wsdl1 1
Discussion – BP1.0 Impact On WSDL1.1
  • BP1.0 provides many valuable clarifications on use of WSDL1.1. These clarifications should be reflected in all WSDL examples in BPEL spec
  • The following BP1.0 constraints affect portType definitions and should be considered for BPEL
    • XML1.0 is mandated for WSDL definitions - OK
    • XML schema is the only conformant type system - OK
    • Disallow operation overloading - operation name must be unique within a portType – should be enforced
    • Disallow out-bound operations – OK
  • The following constraints are for bindings, there is no direct conflicts with BPEL
    • SOAP over HTTP is the only conformant binding –OK, we only provide conformant portType definition, bindings are up to the services implementers.
    • Disallows (soap) encoding – OK, same as above
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