How to write a code in BI Publisher to have Parent, Child and grand child data in a in a single reco

How to write a code in BI Publisher to have Parent, Child and grand child data in a in a single record set?

We have a requirement where we need to implement a report similar to the Combined DataStream Report of Actuate.

I have a Parent BC(P1),Child BC having values(C1,C2),and grandchild having values(G11,G12,G21,G22)

I need a report to implement a output like

P1C1G11
P1C1G12
P1C2G21
P1C2G22

Eg.Take the case of Order,Line Items and Line Item Attributes

Please let me know how can we implement the same, since there is no information available in Siebel bookshelf also regarding the same.