REQUIRES specification <...> ;

REQ specification <...> ;

activity = (resource <, ...>)

where activity represents a single activity or a list of activities. Likewise resource represents a single resource or a list of resources.

The REQUIRES statement defines the potential activity assignments with respect to the pool of resources. If an activity is not defined, the REQUIRES statement implicitly defines the activity. The order of appearance of the ACTIVITY and REQUIRES statements and ACTIVITY dataset affect the DET strategy. For example, to specify that activity A requires resource R, you would need the following statements:

   activity A;
   resource R;
   requires A = (R);

Sometimes, the assignment might not be established in advance and there might be a set of possible alternates that can satisfy the requirements of an activity. This can be defined by multiple resource specifications separated by commas. For example, to specify that the requirements of activity A could be satisfied by either R1, R2, or R3, you would need the following statements:

   activity A;
   resource R1 R2 R3;
   requires A = (R1, R2, R3);

It is also possible that an activity might require more than one resource simultaneously. The specification is similar, the only difference being that the simultaneous requirement is specified without any commas separating them.

For example, the following statements specify that activity A and B requires resources R1 and R2 simultaneously or resources R3 and R4 simultaneously:

   activity A B;
   resource (R1-R4);
   requires (A B) = ((R1 R2), (R3 R4));