3,951 research outputs found
Logical relations for coherence of effect subtyping
A coercion semantics of a programming language with subtyping is typically
defined on typing derivations rather than on typing judgments. To avoid
semantic ambiguity, such a semantics is expected to be coherent, i.e.,
independent of the typing derivation for a given typing judgment. In this
article we present heterogeneous, biorthogonal, step-indexed logical relations
for establishing the coherence of coercion semantics of programming languages
with subtyping. To illustrate the effectiveness of the proof method, we develop
a proof of coherence of a type-directed, selective CPS translation from a typed
call-by-value lambda calculus with delimited continuations and control-effect
subtyping. The article is accompanied by a Coq formalization that relies on a
novel shallow embedding of a logic for reasoning about step-indexing
Object orientation without extending Z
The good news of this paper is that without extending Z,
we can elegantly specify object-oriented systems, including encapsulation,
inheritance and subtype polymorphism (dynamic dispatch). The
bad news is that this specification style is rather different to normal
Z specifications, more abstract and axiomatic, which means that it is
not so well supported by current Z tools such as animators. It also enforces
behavioural subtyping, unlike most object-oriented programming
languages. This paper explains the proposed style, with examples, and
discusses its advantages and disadvantages
Uniqueness Typing for Resource Management in Message-Passing Concurrency
We view channels as the main form of resources in a message-passing
programming paradigm. These channels need to be carefully managed in settings
where resources are scarce. To study this problem, we extend the pi-calculus
with primitives for channel allocation and deallocation and allow channels to
be reused to communicate values of different types. Inevitably, the added
expressiveness increases the possibilities for runtime errors. We define a
substructural type system which combines uniqueness typing and affine typing to
reject these ill-behaved programs
A Type Language for Calendars
Time and calendars play an important role in databases,
on the Semantic Web, as well as in mobile computing. Temporal data
and calendars require (specific) modeling and processing tools. CaTTS
is a type language for calendar definitions using which one can model
and process temporal and calendric data. CaTTS is based on a "theory
reasoning" approach for efficiency reasons. This article addresses type
checking temporal and calendric data and constraints. A thesis underlying
CaTTS is that types and type checking are as useful and desirable
with calendric data types as with other data types. Types enable
(meaningful) annotation of data. Type checking enhances efficiency and
consistency of programming and modeling languages like database and
Web query languages
Practical Datatype Specializations with Phantom Types and Recursion Schemes
Datatype specialization is a form of subtyping that captures program
invariants on data structures that are expressed using the convenient and
intuitive datatype notation. Of particular interest are structural invariants
such as well-formedness. We investigate the use of phantom types for describing
datatype specializations. We show that it is possible to express
statically-checked specializations within the type system of Standard ML. We
also show that this can be done in a way that does not lose useful programming
facilities such as pattern matching in case expressions.Comment: 25 pages. Appeared in the Proc. of the 2005 ACM SIGPLAN Workshop on
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