abstraction of mapogcsos.c common ogc bits

[Kralidis,Tom [Burlington]]

Hi,

In mapogcsos.c, there exists a function called msSOSException, which
basically returns an exception.

In reality, the exception is as per the OWS Common Specification
(http://www.opengeospatial.org/standards/common) 1.0.0, taking arguments
from the SOS specific error.

Future OGC specifications (including all the OWSs supported by
MapServer) must obey the OWS Common Specification.  Having said this, it
would be a good idea to begin to build this as OWS specs merge to OWS
Common.  Defining a set of msOWSCommon functions would mean simply
calling them in future code of supporting OGC Web Services (i.e. WFS
1.1.0 is already there, in addition to the forthcoming SOS 1.0.0.

What do people think about a generic mapowscommon.c / mapowscommon.h

This file would be a set of routines to cover the OWS Common
Specification, and return XML objects which adhere to OWS Common.

The one immediate issue I would see is how these routines return
objects.

With the exception of SOS, all of the other code for OGC XML is returned
as some sort of msIO_printf.  SOS uses libxml2 to make things happen.

Maybe Assefa/others can provide comments on using libxml2 compared to
msIO_printf for XML.  If it were up to me, I'd go with doing things the
libxml2 way, as msIO_printf can be quite error prone for XML output and
well formedness.  This would of course mean that any future development
of OGC stuff in MapServer would be best to align with the libxml2 way of
doing things.

Comments here?

..Tom