[mapserver-users] ScaleHint

[Daniel Morissette]

Rob Atkinson wrote:
> 
> Yep - ignoring this functionality will definitely make the software less than
> safe to deploy.
> 

Rob,

I'm not sure to understand why deploying a server as it is today would
be unsafe?  Could you please specify the risk?  If there is a problem
(other than the absence of the ScaleHint in the capabilities) I would
like to address it.

Note that in the current implementation if MAXSCALE is exceeded then
the layer is simply not drawn... so if the risk you were expecting was
an overload of hte server then it is not the case.

> Well behaved clients will respect the scale-hint. The mapserver should, IMHO,
> generate an error if the scale hint is exceeded - its not quite as strong as
> that but it really ought to be mandatory behaviour.
> 

I see your point, but I would personally opt for a smoother behavior,
that is: not rendering the layer in the result image if scalehint is
exceeded... the reason being that very simple clients that ignore
scalehint would rather receive a blank image than an error IMHO... and
it is assumed that well behaved clients will *not* request anything
outside of scalehint, so what we do in this case is irrelevant to them.

I haven't found anything in the 1.1.0 spec about what the expected
behavior is when a request outside of scalehint is received... I'll
forward the question to the WMS-Dev list to make sure that what we do in
MapServer is in line with what the others servers do and expect.

-- 
------------------------------------------------------------
 Daniel Morissette               morissette at dmsolutions.ca
 DM Solutions Group              http://www.dmsolutions.ca/
------------------------------------------------------------
  Don't put for tomorrow what you can do today, because if 
      you enjoy it today you can do it again tomorrow.