At least one of minimum, optimum, or maximum IPD must be specified on table - XSL-FO Apache FOP

I am writing an XSL stylesheet for XSL-FO transfomration to create a PDF, with tables, using Apache FOP library. I have succeeded in getting PDF document with data. But having some issues with the layout. The following lines are getting printed t开发者_如何学运维o my Netbeans IDE console, while creating PDF.

[ERROR] At least one of minimum, optimum, or maximum IPD must be specified on table.
[INFO] area contents overflows area in line

My table cell contents are getting overlapped due to this. I want to know what IPD is and how to set it. I am a beginner in using XSL-FO and so any help is highly appreciated.