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Simulations in Coalgebra
 THEOR. COMP. SCI
, 2003
"... A new approach to simulations is proposed within the theory of coalgebras by taking a notion of order on a functor as primitive. Such an order forms a basic building block for a "lax relation lifting", or "relator" as used by other authors. Simulations appear as coalgebras of thi ..."
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A new approach to simulations is proposed within the theory of coalgebras by taking a notion of order on a functor as primitive. Such an order forms a basic building block for a "lax relation lifting", or "relator" as used by other authors. Simulations appear as coalgebras of this lifted functor, and similarity as greatest simulation. Twoway similarity is then similarity in both directions. In general, it is different from bisimilarity (in the usual coalgebraic sense), but a su#cient condition is formulated (and illustrated) to ensure that bisimilarity and twoway similarity coincide. Also, suitable conditions are identified which ensures that similarity on a final coalgebra forms an (algebraic) dcpo structure. This involves a close investigation of the iterated applications F (#) and F (1) of a functor F with an order to the initial and final sets.
Proof Principles for Datatypes with Iterated Recursion
, 1997
"... . Data types like trees which are finitely branching and of (possibly) infinite depth are described by iterating initial algebras and terminal coalgebras. We study proof principles for such data types in the context of categorical logic, following and extending the approach of [14, 15]. The technica ..."
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Cited by 17 (3 self)
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. Data types like trees which are finitely branching and of (possibly) infinite depth are described by iterating initial algebras and terminal coalgebras. We study proof principles for such data types in the context of categorical logic, following and extending the approach of [14, 15]. The technical contribution of this paper involves a description of initial algebras and terminal coalgebras in total categories of fibrations for lifted "datafunctors". These lifted functors are used to formulate our proof principles. We test these principles by proving some elementary results for four kinds of trees (with finite or infinite breadth or depth) using the proof tool pvs. 1 Introduction Algebras and coalgebras are of wellestablished importance in computer science, notably in the theory of datatypes, where especially initial algebras and terminal coalgebras play a distinguished role. Over the past decade there is more and more interest in the logic associated with initial algebras and ter...
A methodology for proving control systems with Lustre and PVS
, 1999
"... In this paper, we intend to show how to use the synchronous dataflow language Lustre, combined with the PVS proof system in deriving provablycorrect (distributed) control programs. We hopefully illustrate, based on a railway emergency braking system example, the features of our approach  asynchr ..."
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Cited by 9 (1 self)
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In this paper, we intend to show how to use the synchronous dataflow language Lustre, combined with the PVS proof system in deriving provablycorrect (distributed) control programs. We hopefully illustrate, based on a railway emergency braking system example, the features of our approach  asynchronous periodic programs with nearly the same period, communicating by sampling  equational reasoning which leaves to the Lustre compiler the task of scheduling computations  no distinction between control programs and physical environments which are sampled in the same way. This allows us to provide "elementary " proofs based on difference equations instead of differential ones which require more involved PVS formalization. 1 Introduction Control systems form an important class of critical computer systems: it is in this domain that some of the most critical applications can be found, for instance in civil aircrafts, ground transportation, nuclear power etc. Thus, a lot of activity ha...
Total correctness refinement for sequential reactive systems
 In proceedings of TPHOLs 2000. (13th International Conference on Theorem Proving in Higher Order Logics), number 1869 in LNCS
, 2000
"... Abstract. We introduce a coinductivelydefined refinement relation on sequential nondeterministic reactive systems that guarantees total correctness. It allows the more refined system to both have less nondeterminism in its outputs and to accept more inputs than the less refined system. Data reifi ..."
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Cited by 3 (0 self)
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Abstract. We introduce a coinductivelydefined refinement relation on sequential nondeterministic reactive systems that guarantees total correctness. It allows the more refined system to both have less nondeterminism in its outputs and to accept more inputs than the less refined system. Data reification in VDM is a special case of this refinement. Systems are considered at what we have called fine and medium levels of granularity. At the finegrain level, a system’s internal computational steps are described. The finegrain level abstracts to a mediumgrain level where only input/output and termination behaviour is described. The refinement relation applies to medium grain systems. The main technical result of the paper is the proof that refinement is respected by contexts constructed from fine grain systems. In other words, we show that refinement is a precongruence. The development has been mechanized in PVS to support its use in case studies. 1
(中山大 学 计算机科学系,广 东 广 州 510275) A Survey on the Coalgebraic Methods in Computer Science
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Towards a Customizable PVS
, 2000
"... PVS is a stateoftheart theoremproving tool developed by SRI International. It is used inavariety of academic and realworld applications by NASA and ICASE researchers, for whom tool customization and extensibility are becoming increasingly important issues. This paper shows, by referring to past ..."
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PVS is a stateoftheart theoremproving tool developed by SRI International. It is used inavariety of academic and realworld applications by NASA and ICASE researchers, for whom tool customization and extensibility are becoming increasingly important issues. This paper shows, by referring to past experiences with several projects and case studies, that the customization features currently offered by PVS are often insufficient. It also suggests several improvements regarding PVS's customization in the short run and regarding its extensibility in the long run.
The NASA STI Program Office provides
, 2001
"... Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the l ..."
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Since its founding, NASA has been dedicated to the advancement of aeronautics and space science. The NASA Scientific and Technical Information (STI) Program Office plays a key part in helping NASA maintain this important role. The NASA STI Program Office is operated by Langley Research Center, the lead center for NASA's scientific and technical information.
A PVS Proof Obligation Generator for Lustre Programs
 Universite ParisSud
, 2000
"... . This paper presents a tool for proving safety properties of ..."