default value if not specified¶

Multiplicity¶

Each relation has a multiplicity, which represents how many atoms it can include. If you do not include a multiplicity, it’s assumed to be one for individual relations and set for Multirelations.

Reference source (1)

Alloy Documentation

sig Key {}

sig Lock {
  key: Key
  // synonymous with: 
  // key: one Key 
}

sig A, B {}

sig S {
  r: A -> B
  // synonymous with: 
  // r: A set -> set B
}