[Pig-user] Converting an inner bag

I have a simple schema that contains an inner bag. What I need to
essentially do is that for each tuple in the inner bag, I need to create a
new tuple in a new outer bag. This is easier shown than explained! Consider
the following schema and data:

DESCRIBE A;
A: {id: chararray, items: {item: chararray}}

DUMP A;
(a1, {(i1), (i2), (i3)})
(a2, {(i1), (i2), (i3)})

This needs to turn into some relation, I that looks like:

DESCRIBE I;
I: {id: chararray, item: chararray}

DUMP I;
(a1, i1)
(a1, i2)
(a1, i3)
(a2, i1)
(a2, i2)
(a2, i3)

...so that I can then do a join with another relation X against the item
field from I.

Any ideas? Hope that description made sense.

Many thanks,

Josh