Folks,
In some ways, I'm glad I was on vacation while much of this debate
raged!! ;-)
Comments below.....
Jean-Sebastien Delfino wrote:
[A] What we have right now, standard SCA extensions and tuscany
extensions sharing the standard SCA namespace
(B) What IMO is a more correct use of XML namespaces, standard SCA
extensions in the standard SCA namespace, and Tuscany extensions in a
Tuscany namespace
[C] What an application developer could write if we allowed namespaces
to be omitted
......
Now here are a few "side effects" :)
Option [A]
- I cannot validate this composite against the standard SCA schemas
(it'll show errors in my XSD aware XML editor) our Tuscany extensions
violate the standard SCA namespace
- I have one less namespace and prefix declaration to care about
Option [B]
- I can validate this composite against the standard SCA schemas, as the
Tuscany extensions match the xsd:any namespace="##other" extensibility
points in the SCA schema
- I have one more namespace and prefix declaration to write covering the
Tuscany extensions
Option [C]
- I don't need to worry about namespaces, which are usually long and
error prone, writing the composite is simpler
- I cannot validate this composite against the standard SCA schemas as
it does not declare namespaces
My preference is to do both:
- [B], be correct with respect to our usage of XML schema, to make
people who care about XML schema validation and use XML schema tools happy
- and [C] allow people who don't like namespaces to not have to write them
Why do I like [C] as well? Here are a few examples:
<html>
<body>
Hello! I can write XML without namespaces, isn't that nice?
</body>
</html>
An axis2.xml configuration file
http://svn.apache.org/repos/asf/incubator/tuscany/java/sca/modules/binding-ws-axis2/src/main/resources/org/apache/tuscany/sca/binding/axis2/engine/config/axis2.xml
An MS WCF configuration
http://msdn2.microsoft.com/en-us/library/ms735103.aspx
A Tomcat server.xml file
http://tomcat.apache.org/tomcat-6.0-doc/default-servlet.html
All work without namespaces...
Let me tackle them in reverse order (the more debateable first....)
C) Yes, this is indeed simpler. No namespaces is wonderful. (PS I will
declare here that I am no fan of XML, so less XML always keeps me happy)
The downside of this is that it "assumes" that you know all the valid
XML in advance, if any validation is going to be done. I suppose that
you have options:
- 1. Don't worry about validation at all.
- 2. Do validation and have some non-namespace way of knowing all the
XSDs that contribute.
The problem really hits when you start to build SCA Assemblies using
tooling that is not part of Tuscany. The SOA Tools project at Eclipse
comes to mind. We may come up with some approach for Tuscany, but can
that also be used for the SOA Tools project?
Namespaces may be ugly but at least they represent a standard that all
can use....
B) This is the SCA spec approach. I'd recommend at least supporting
this even if other techniques are also allowed.
A) Is really problematic. It implies hacking the XSDs defined by the
SCA specs. How will anyone know when they have violated the spec XSDs
that form part of the Portability conformance that is part of the value
of SCA (ie build and run my stuff on Tuscany and the same stuff should
work on Oracle's runtime, if I stick to the stuff defined in the SCA
specs...).
A will also imply the existence of at least 2 sets of "SCA XSDs" - the
spec ones and the Tuscany ones. How will anyone know which one they've
got in their hands....?
So:
A) -1 not a good place to be
B) +1 its the standard
C) +0.5 I can envisage this as +1 if it is an optional setting that a
user can knowingly choose to use - as long as it is clear what they lose
Yours, Mike.
PS The Microsoft WCF config works without a namespace since I think it
is not extensible, unlike SCA which allows all kinds of extension.
PS 2 If anyone can think of a better way for SCA to handle its
extensibility, that will allow us to drop namespaces, the spec team will
be all ears. The spec group debated the use of namespaces at some
length before adopting the current spec definition (and I was one of
those trying to keep namespaces out of it....).
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