Let's say I want to use WRS to let the users see several statics reports and graphics. Each of them are unique and updated each month.
I don't want to create infomaps.
Can I create as many SP than I have reports and graphics and call them within WRS without to create an InfoMap for that ? I mean with "within WRS" that each report created by one SP will be call in one "cell" of a report page.
If you use Stored Processes (SP) then you do not need to define Information Maps. That is one way to design your WRS reports. Remember that when the user clicks 'View Report' that each SP will then execute, and if you have input parameters set, the users will have to provide their choices for the input parameters before they will see the report.
Of course, if this is some kind of monthly or regular report, then perhaps you will not need to prompt them for input parameters.
However, one benefit of having Information Maps is that if your users wanted to filter on one group over another for a graph or report -- in an adhoc way -- they could do this if the WRS report was created from an Info Map. But with an SP, they do not have any interactivity or interface to the graph or the report itself except through the input parameters.
I'd recommend a few test reports to see whether the users prefer the SP version of the report or the Info Map based version of the report.
An OLAP cube does need an information map for WRS. You build the info map and define the particular "slices" of the cube that will populate the report. Then when the user opens up WRS and picks that info map as the data source, the relevant slices will get pulled into the report.