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Re: Proposal for hierarchical fault codes

From: Martin Gudgin <marting@develop.com>
Date: Tue, 6 Nov 2001 22:03:14 -0000
Message-ID: <003001c1670e$d6d215e0$977ba8c0@greyarea>
To: "Jacek Kopecky" <jacek@systinet.com>
Cc: "XML Protocol Discussion" <xml-dist-app@w3.org>




----- Original Message -----
From: "Jacek Kopecky" <jacek@systinet.com>
To: "Martin Gudgin" <marting@develop.com>
Cc: "XML Protocol Discussion" <xml-dist-app@w3.org>
Sent: Tuesday, November 06, 2001 9:22 AM
Subject: Re: Proposal for hierarchical fault codes


> Gudge,
>  Is there a possibility to make it the following way?
>
> <soap:Fault xmlns:soap='http://www.w3.org/2001/09/soap-envelope' >
>   <faultcode>
>     soap:Receiver
>     <faultcode xmlns:app='http://example.org/apps'>
>       app:SomeError
>     </faultcode>
>   </faultcode>
> </soap:Fault>
>
>  I admit I don't know XML Schema enough to know the answer
> myself.
>  This way would be backwards compatible in the simple cases of no
> nested faultcodes.

I did consider the approach you suggest. I rejected it because there is (
currently ) no way to assign a type to the text content of <faultcode> in
such a design. That is, there is no way to say that the text must be a
QName. This is a problem/design choice regarding mixed content in XML
Schema.


>  If this is not possible, I think I'd slightly prefer the
> attribute way as well, because I don't see us ever needing to add
> structure to the value of faultcode, or additional attributes.

I agree, QName plus the nesting capability certainly seems like
extensibility enough.

> We're keeping the detail element, aren't we? 8-)

Yes.

>  Anyway, if enough people feel the element way is necessary, so
> be it, I guess. 8-)
>  Thanks for putting this together. 8-)

My pleasure

Gudge


>
>                    Jacek Kopecky
>
>                    Senior Architect, Systinet (formerly Idoox)
>                    http://www.systinet.com/
>
>
>
> On Mon, 5 Nov 2001, Martin Gudgin wrote:
>
>  >
>  > Here are two proposals for hierarchical fault structures. There are
provided
>  > in response to issue 130[1] which is about the current hierarchical
fault
>  > code structure in SOAP. SOAP currently uses a 'dotted' notation for
>  > hierarchical fault codes, specifically for the Client and Server
'classes'
>  > of fault. This proposal asserts that it is better to use the
hierarchical
>  > nature of XML to build such fault codes rather than requiring
applications
>  > to micro-parse element content. Other advantages include;
>  >
>  > 1. because each faultcode is a QName, there is much better support for
>  > ensuring that applications do not define identical fault codes.
>  >
>  > 2. applications recieving such faults are not required to understand
every
>  > fault code, they can interpret the higher levels of fault and ignore
the
>  > more nested fault codes if they do not understand them. This should
make
>  > processing faults more straightforward as an application can just look
at
>  > the highest level faultcode to begin with then decide whether it wants
to
>  > 'drill down' into the more nested information.
>  >
>  > In addition issue 143[2] requires a resolution of the names
Client/Server.
>  > This proposal suggests that 'Sender' be substituted for 'Client' and
>  > 'Receiver' be substituted for 'Server'. Hence the examples below use
>  > 'soap:Receiver'
>  >
>  >
>  >
>  > This first example puts the value of the faultcode in a child element
with a
>  > local name of 'value';
>  >
>  > <soap:Fault xmlns:soap='http://www.w3.org/2001/09/soap-envelope' >
>  >   <faultcode>
>  >     <value>soap:Reciever</value>
>  >     <faultcode>
>  >       <value xmlns:app='http://example.org/apps' >app:SomeError</value>
>  >     </faultcode>
>  >   </faultcode>
>  > </soap:Fault>
>  >
>  > The schema description looks like this;
>  >
>  > <xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'
>  >            xmlns:tns='http://www.w3.org/2001/09/soap-envelope'
>  >            targetNamespace='http://www.w3.org/2001/09/soap-envelope' >
>  >
>  >   <xs:complexType name='faultcodeType' >
>  >     <xs:sequence>
>  >       <xs:element name='value' type='xsd:QName' />
>  >       <xs:element name='faultcode' type='tns:faultcodeType'
minOccurs='0' />
>  >     </xs:sequence>
>  >   </xs:complexType>
>  >
>  > </xs:schema>
>  >
>  >
>  >
>  >
>  > This second example puts the value of the fault code in an attribute
with a
>  > localname of 'value';
>  >
>  > <soap:Fault xmlns:soap='http://www.w3.org/2001/09/soap-envelope' >
>  >   <faultcode value='soap:Reciever' >
>  >     <faultcode xmlns:app='http://example.org/apps'
value='app:SomeError' />
>  >   </faultcode>
>  > </soap:Fault>
>  >
>  >
>  > The schema description looks like this;
>  >
>  > <xs:schema xmlns:xs='http://www.w3.org/2001/XMLSchema'
>  >            xmlns:tns='http://www.w3.org/2001/09/soap-envelope'
>  >            targetNamespace='http://www.w3.org/2001/09/soap-envelope' >
>  >
>  >   <xs:complexType name='faultcodeType' >
>  >     <xs:sequence>
>  >       <xs:element name='faultcode' type='tns:faultcodeType'
minOccurs='0' />
>  >     </xs:sequence>
>  >     <xs:attribute name='value' type='xsd:QName' use='required' />
>  >   </xs:complexType>
>  >
>  > </xs:schema>
>  >
>  >
>  > I have a mild preference for the latter approach.
>  >
>  >
>  > Comments, flames, etc to the usual address
>  >
>  > Martin Gudgin
>  > DevelopMentor
>  > http://www.develop.co.uk
>  >
>  >
>  > [1] http://www.w3.org/2000/xp/Group/xmlp-issues.html#x130
>  > [2] http://www.w3.org/2000/xp/Group/xmlp-issues.html#x143
>  >
>
Received on Tuesday, 6 November 2001 17:04:04 GMT

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