[ome-devel] ome access with c++

[Harry Hochheiser]

Gerhard:

The third parameter to your method call (after the session key and  
the method) is the specification of the fields that are wanted ( for  
proof of this,, look at the definition of getUserState in  
SessionFacade.pm).

The FieldsSpecification is a flexible way to specify exactly which  
components of a complex tree of objects that you want to retrieve in  
a given situation. The OME UserState (implemented in the database in  
the ome_sessions table) contains some basic information (an Id, a  
session-key, started and last accessed timestamps, etc.) along with  
references to items from other tables (group, experimenter, dataset,  
image, project, etc.) The fields specification criteria tells us  
which of the fields that we should retrieve, and which tables we  
should join in to retrieve requested values. In effect, the fields  
specification acts as both a project and a select off of the basic  
table that is requested.

The "." notation specifies the top-level fields that should be  
retrieved: the columns from the table in question. In your example,  
we have a member with name "." and values "id" and "experimenter".  
This indicates that we should get the Id of the user state, and the  
experimenter along with that. If we had wanted (for example) the  
started timestamp as well, we would have specified "started" as an  
additional item in the array.

The other element in the array - "experimenter" specifies the fields  
that we want to retrieve for the experimenter: in this case, just the  
id. We could have asked for the first name or last name of the  
experimenter by adding other fields. underneath experimenter.

This can proceed in an arbitrarily complex fashion by adding dotted  
pair notation for further nesting. Thus, if i had asked for "dataset"  
under the ".", i would have had a top-level member named "dataset",  
which might have had fields like "id" and "owner".  i might then have  
had another top-level entry called "dataset.owner", which would ask  
for "id" "first name", "last name', etc.

This may be a somewhat cryptic set of conventions, but it's very  
flexible and powerful.  if you have any further questions, please ask.

You might also consider looking at some useful notes on the remote  
framework, at http://www.openmicroscopy.org/api/remote/transfer.html

best,

harry







On Oct 12, 2005, at 6:39 AM, gerhard wrote:

> One more question to  XML-RPC:
>
> I have the following code:
>
> <value>getUserState</value></param>
> <param>
> <value>
> <struct>
>       <member><name>experimenter</ 
> name><value><array><data><value>id</value><value>Group</ 
> value><value>FirstName</value><value>LastName</value></data></ 
> array></value></member>
>
>       <member><name>.</ 
> name><value><array><data><value>experimenter</value></data></ 
> array></value></member>
> </struct></value></param>
> </params>
> </methodCall>
>
>
> So if anyone can explain the meaning of the two members in the  
> struct. I
> know that these lines are what I want to get. But especially the  
> second
> member with the point is confusing for me. So if anyone can   
> explain it
> in detail.
>
> Thanks very much
> gerhard
>

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