David Cooper and Susan Stepney.
Segregation with Communication.

In Jonathan P. Bowen, Steve Dunne, Andy Galloway, Steve King, editors, ZB2000: First International Conference of B and Z Users, York, UK, August 2000 . LNCS 1878:451--470. Springer, 2000.

Abstract:

We have developed a general definition of segregation in the context of Z system specifications. This definition is general enough to allow multi-way communications between otherwise segregated parties along defined channels. We have an abstract definition of segregation in terms of the traces allowed by systems, a concrete style of specification to ensure segregation (a generalisation of promotion that we call multi-promotion ) and a proof that unconstrained multi-promotion is a sufficient condition to ensure segregation.

More on the

@inproceedings(SS-ZB2000a,
  author = "David Cooper and Susan Stepney",
  title = "Segregation with Communication",
  pages = "451--470",
  crossref = "ZB-00"
)

@proceedings(ZB2000,
  title = "ZB2000: First International Conference of B and Z Users,
           York, UK, August 2000",
  booktitle = "ZB2000: First International Conference of B and Z Users,
               York, UK, August 2000",
  editor = "Jonathan P. Bowen and Steve Dunne and Andy Galloway and Steve King",
  series = "LNCS",
  volume = 1878,
  publisher = "Springer",
  year = 2000
)