40,061 research outputs found
Flexible Invariants Through Semantic Collaboration
Modular reasoning about class invariants is challenging in the presence of
dependencies among collaborating objects that need to maintain global
consistency. This paper presents semantic collaboration: a novel methodology to
specify and reason about class invariants of sequential object-oriented
programs, which models dependencies between collaborating objects by semantic
means. Combined with a simple ownership mechanism and useful default schemes,
semantic collaboration achieves the flexibility necessary to reason about
complicated inter-object dependencies but requires limited annotation burden
when applied to standard specification patterns. The methodology is implemented
in AutoProof, our program verifier for the Eiffel programming language (but it
is applicable to any language supporting some form of representation
invariants). An evaluation on several challenge problems proposed in the
literature demonstrates that it can handle a variety of idiomatic collaboration
patterns, and is more widely applicable than the existing invariant
methodologies.Comment: 22 page
Free composition instead of language dictatorship
Historically, programming languages have been—benevolent—dictators: reducing all possible semantics to specific ones offered by a few built-in language constructs. Over the years, some programming languages have freed the programmers from the restrictions to use only built-in libraries, built-in data types, and builtin type-checking rules. Even though—arguably—such freedom could lead to anarchy, or people shooting themselves in the foot, the contrary tends to be the case: a language that does not allow for extensibility is depriving software engineers of the ability to construct proper abstractions and to structure software in the most optimal way. Therefore the software becomes less structured and maintainable than would be possible if the software engineer could express the behavior of the program with the most appropriate abstractions. The idea proposed by this paper is to move composition from built-in language constructs to programmable, first-class abstractions in a language. We discuss several prototypes of the Co-op language, which show that it is possible, with a relatively simple model, to express a wide range of compositions as first-class concepts
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