This example demonstrates intersections.

In order to buy rockets from Acme, you must be BOTH a preferred customer
AND a WarnerBros character. In this example, the following query will be
successful:

    Acme.buy_rockets <-?- Coyote

The following query will fail (because Batman does not have the
attribute WarnerBros.character):

    Acme.buy_rockets <-?- Batman

Acme.buy_rockets <- Acme.preferred_customer & WarnerBros.character
Acme.preferred_customer <- Coyote
Acme.preferred_customer <- Batman
WarnerBrothers.character <- Coyote

creddy --generate --cn Acme

creddy --generate --cn WarnerBros

creddy --generate --cn Coyote

creddy --generate --cn Batman

creddy --attribute \
       --issuer Acme_ID.pem --key Acme_private.pem --role buy_rockets \
       --subject-cert Acme_ID.pem --subject-role preferred_customer \
       --subject-cert WarnerBros_ID.pem --subject-role character \
       --out Acme_buy_rockets__Acme_preferred_customer_and_WarnerBros_character_attr.der

creddy --attribute \
       --issuer Acme_ID.pem --key Acme_private.pem --role preferred_customer \
       --subject-cert Coyote_ID.pem \
       --out Acme_preferred_customer__Coyote_attr.der

creddy --attribute \
       --issuer Acme_ID.pem --key Acme_private.pem --role preferred_customer \
       --subject-cert Batman_ID.pem \
       --out Acme_preferred_customer__Batman_attr.der

creddy --attribute \
       --issuer WarnerBros_ID.pem --key WarnerBros_private.pem --role character \
       --subject-cert Coyote_ID.pem \
       --out WarnerBros_character__Coyote_attr.der