Many to many mapping matrix issue

Hi there. I have a data table which contains mappings of topics to categories, e.g:

  Y Z
A Yes  
B Yes Yes

Where'Yes' indicates the topic belongs to the category.

I want to unwind this table to a list of pairs of topics and categories like this:

Topic Category
A Y
B Y
B Z

And possibly call a REST service for every pair. I'm not quite sure how to go about this in Knime, will I need to use workflow and loops?

The unpivoting node can do this.
 

Thanks Iris, that worked a treat. I'd looked at unpivot but passed over it.

Even better, with Skip rows containing missing cells ticked I don't even have to filter the resulting table. :-)