Tω as a Stable Universal Domain

  • Authors:
  • Haoran Zhao;Hui Kou

  • Affiliations:
  • -;-

  • Venue:
  • Electronic Notes in Theoretical Computer Science (ENTCS)
  • Year:
  • 2014

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Abstract

In the seventies, G. Plotkin noticed that T^@w, the cartesian product of @w copies of the 3 elements flat domain of Boolean, is a universal domain, where ''universal'' means that the retracts of T^@w in Scott's continuous semantics are exactly all the @wCC-domains, which with Scott continuous functions form a cartesian closed category. As usual ''@w'' is for ''countably based'', and here ''CC'' is for ''conditionally complete'', which essentially means that any subset which is pairwise bounded has an upper bound. Since T^@w is also an @wDI-domain (an important structure in the stable domain theory), a problem arises naturally: Is T^@w a universal domain for Berry's stable semantics? The aim of this paper is to answer this question. We investigate the properties of stable retracts and introduce a new domain named a conditionally complete DI-domain (a CCDI-domain for short). We show that, (1) a dcpo is a stable retract of T^@w if and only if it is an @wCCDI-domain; (2) the category of @wCCDI-domain (resp. CCDI-domains) with stable functions is cartesian closed. So, the problem above has an affirmative answer.