SIAP and previews

[Ray Plante]

Hey Anita,

On Thu, 30 Sep 2004, Anita Richards wrote:
> SIAP v1.0 looks very suitable forradio data including 'virtual' images
> which are created on demand from visibility data.  However in Section  3.
> "Image Service Types" I am not sure how to indicate that more than one of
> the subgroups 1-4 might be available from a single archive.  At present 4.
> Pointed Image Archive states that if the archive also contains surveys
> that should be registered separately.  Does this cover the situation where
> you have e.g. virtual images available for a collection of 10' fields of
> view, and 10" ready made images for the centre of each field? 

Each Image Service Type represents a different kind of behavior of the 
SIAP serivce.  If, hypothetically speaking, you had an implementation that 
qualified as being more that one service type, the service input interface 
does not allow the user to specify which behavior (e.g. cutout, 
mosaic--your generation of "virtual" images, static image retrieval).  In 
my mind this is not a bug, but rather a feature.  It allows the same query 
to be sent any SIAP service of any type.  Image generation paramters not 
supported by pointed archive types are ignored.  

Thus, in the SIA model, users that wish to select only certain behaviors
(e.g. cutout types), they filter via service selection with the registry.  
That is, if you want to support both on-the-fly creation of virtual images
(a Mosaic type) and a static image behavior (Atlas or Pointed), then you
register each as separate resources.  Of course, you can use a single
implementation for each one; just include an argument that selects the
image service type behavior in the registered base URL.

> Is there a need for a category 5. Preview or is this covered by 4.? - will
> users realise that they might also be able to look for customised images?

Previews are recognized by their FORMAT being labeled as a graphics image 
types (JPEG, PNG, GIF).  The FORMAT input allows one to select only 
previews.  Thus, I see this as an independent axis to the service type.  
As an example, some cutout services are able to create JPEG previews that 
are made "to order".  

cheers,
Ray