Problems about the Spectrum Data Model from the view of a Web Service programmer

[Guy Rixon]

On Thu, 14 Sep 2006, Dobos, Laszlo wrote:

> * 1. XML serialization puts the value of the fields between opening and
> closing tags. It's okay for an XML document, but SOAP (the web services XML
> protocoll) can deserialize _only strings_ if they're written between the
> tags and other attributes are also specified at the same time. The correct
> way to store values is in elements, like
>
> 	<Wavelength>
> 		<Unit>nm</Unit>
> 		<Value>700</Value>
> 	</Wavelength>
>
> or store in attributes, like
>
> 	<Wavelength Unit="nm" Value="700" />
>
> But the following is not correct:
>
> 	<Wavelength Unit="nm">700</Wavelength>
>
> We should keep in mind that even though this third version looks nicer in a
> text editor, XML is nor for reading by humans, but for using in web
> services, so I suggest to follow the SOAP standard instead of making good
> looking documents.

>From where do you get this ruling?  I've just looked up the W3C recommendation
for SOAP 1.2 (http://www.w3.org/TR/soap12-part1/#soapbodyel) and it says
(section 5.3.1):

"All child element information items of the SOAP Body element information
item:

SHOULD have a [namespace name] property which has a value, that is the name of
the element SHOULD be namespace qualified.

Note:

Namespace qualified elements tend to produce messages whose interpretation is
less ambiguous than those with unqualified elements. The use of unqualified
elements is therefore discouraged.

MAY have any number of character information item children. Child character
information items whose character code is amongst the white space characters
as defined by XML 1.0 [XML 1.0] are considered significant.

MAY have any number of element information item children. Such element
information items MAY be namespace qualified.

MAY have zero or more attribute information items in its [attributes]
property. Among these MAY be the following, which has special significance for
SOAP processing:

encodingStyle attribute information item (see 5.1.1 SOAP encodingStyle
Attribute)."

I.e. any mix of text, attribute and element content is allowed. Which SOAP
standard are you looking at?

If you meant that mixes of element and attribute children are not allowed in
rpc/encoded style (I don't know whether this is true), then let's not worry
about that, because rpc/encoded is deprecated (in the WS-I basic profile and
therefore in the IVOA Basic Profile for SOAP) and we shouldn't use it.

If you meant that .NET doesn't support mixed content, then we can consider
accomodating such a broken toolkit (as we do by using "wrapped"
document/literal in other services), but it's not obvious that we should do
so.

If you meant that the WS-I basic profile has a ruling against mixed content,
then we should take that seriously.

Please clarify.

Guy Rixon 				        gtr at ast.cam.ac.uk
Institute of Astronomy   	                Tel: +44-1223-337542
Madingley Road, Cambridge, UK, CB3 0HA		Fax: +44-1223-337523