[fdo-internals] New RFC posted

[Thomas Knoell]

Hi Frank

The FdoFunctionDefinition allows a provider to define a set of supported
expression functions. The list is accessible as part of the expression
capabilities that can be retrieved from a connection. The idea behind
this new property is to allow for a consumer of the list to sort them
according to their class. This may help presenting them in a user
defined UI as similar functions can be grouped. It is also part for the
re-engineering of the expression engine.

As you pointed out, the implementation of this enhancement will not
require any changes to current providers if they select not to use this
enhanced feature.

I'll update the RFC to include the information.

Thanks

  Thomas


-----Original Message-----
From: fdo-internals-bounces at lists.osgeo.org
[mailto:fdo-internals-bounces at lists.osgeo.org] On Behalf Of Frank
Warmerdam (External)
Sent: Tuesday, July 17, 2007 3:37 PM
To: FDO Internals Mail List
Subject: Re: [fdo-internals] New RFC posted

Thomas Knoell wrote:
> Hi,
> 
>  
> 
> A new RFC (*/FDO RFC 5/*) to enhance the FDO API for a function 
> definition has been posted. Please review the RFC and let me know if 
> additional information is required to make a final decision on the
RFC.

Folks,

For those who might like to know before digging into this RFC, it adds
a means to classify FdoFunctionDefinitions, for instance as Aggregate,
Conversion, Date, Math, Numeric, String or Unknown.  The RFC can be
directly accessed at:

   http://trac.osgeo.org/fdo/wiki/FDORfc5

Thomas, can you comment on the rationale and use of this new
classification
system?  I'm also embarrassed to admit I don't know anything about the
role
of these FdoFunctionDefinitions.  Are these functions that can be
applied in
expressions on attributes of features for attribute filters?

I'm pleased to see that the change adds a defaulted parameters, and so
presumably doesn't require changes in providers or most other code.  I
do
think think it is worth mentioning that this is an ABI change, and
(presumably)
that it will be introduced into FDO Trunk.

I'd be +0 on the RFC if we had started voting.

Best regards,
-- 
---------------------------------------+--------------------------------
------
I set the clouds in motion - turn up   | Frank Warmerdam,
warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo,
http://osgeo.org

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