Projects and work orders

Hi All,

I have a requirement to come up with a report related to PS module.

the requirement is like this:

I have to report actual cost information for a given project, work order, WBS elements,

Activities and sub activities for each cost element (material, labor etc).

in SBC I am able to find cost information at Project, WBS element, activities and sub-activities in one Datasource.

and cost information at work order level in other data source.

I need to understand and establish a link between work orders and projects, how they are related and what linking is the linking object.

Any help from expert who worked in PS/PM/CO modules.

regards

Ram