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Re: Famous web services with apparent serious XML schema error

• To: <xml-dev@l...>
• Subject: Re: Famous web services with apparent serious XML schema errors
• From: "Bob Cunnings" <cunnings@w...>
• Date: Sat, 11 Jan 2003 19:34:15 -0700
• References: <042a01c2b9d3$abb3cac0$af00a8c0@jmg>

Hi,

> I'm working on an application that needs to be able to read and rely on
the
> XML Schema information contained in or referenced from web service
> descriptions (WSDL), since it is supposed to be able to dynamically
interact
> with any web service so specified.  While this is possible with many web
> services, it seems that developers of these descriptions sometimes
propagate
> a common set of what I believe to be erroneous schema constructs and
usages.
> The the schemas are
> a.  invalid
> b.  fail to define the types that were intended
> and the instances returned from the web services are invalid with respect
to
> the schemas.
>
> The common errors (if I am not confused!) are:
>
> 1.  Using the http://schemas.xmlsoap.org/soap/encoding/ namespace (the URL
> can be dereferenced to get the schema) and referring to its types without
an
> <import> in the schema.  The schema thus will not be accepted by a schema
> validator.

Yes, it's common.

> 2.  Definition of array types based on the soap encoding, like this:
> <xsd:complexType name="AuthorArray">
>     <xsd:complexContent>
>      <xsd:restriction base="soapenc:Array">
>       <xsd:attribute ref="soapenc:arrayType"
wsdl:arrayType="xsd:string[]"/>
>      </xsd:restriction>
>     </xsd:complexContent>
> This derivation fails to copy the unchanged content from soapenc:Array
> (basically a repeating <any>), so instead of defining a homogeous array,
it
> specifies empty content..[1]  Xerces tells me so when I hand it an
instance:
>

This manner of  "derivation" is found in the WSDL 1.1 spec. See bullet three
under:

http://www.w3.org/TR/wsdl#_types

and look at examples such as Example 5. An often cited critique of this can
be found within:

http://www.capescience.com/articles/commonerrors/index.shtml

This has been the cause of quite a bit of debate in the past on various
lists. The consensus by implementors of WSDL processors seems to be to adopt
it as given in the WSDL 1.1 spec for until something better comes along. The
argument was that the definition for a SOAP encoded array wasn't to be used
for validation. A typical expression of this pov is found at:

http://groups.yahoo.com/group/soapbuilders/message/5855

RC

• References:
  • Famous web services with apparent serious XML schema errors
    • From: "Jeff Greif" <jgreif@a...>

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