Re: finding gems by all of the same authors?

[Olivier Corby]

Hi,

What Gems were written by all of the same authors?
That is, if this Gem was written by Alice and Bob, I want
to find others that were also written only by these two.

You need to check that every author of foo is author of Gem and 
conversely that every author of Gem is author of foo.

Regards,

Olivier



SELECT DISTINCT ?gem
WHERE {
item:foo-1.2.3-x86  spec:author  ?author
?gem                spec:author  ?author

filter(?gem != item:foo-1.2.3-x86)

filter not exists {
  item:foo-1.2.3-x86  spec:author  ?author2
  filter not exists {?gem    spec:author  ?author2}
}

filter not exists {
  ?gem  spec:author  ?author2
  filter not exists {item:foo-1.2.3-x86  spec:author  ?author2}
}
}