145 research outputs found
Semantics, Implementation and Pragmatics of Clear, a Program Specification Language
Specifications are necessary for communicating decisions and
intentions and for documenting results at many stages of the program
development process. Informal specifications are typically used
today, but they are imprecise and often ambiguous. Formal
specifications are precise and exact but are more difficult to write
and understand. We present work aimed toward enabling the practical
use of formal specifications in program development, concentrating
on the Clear language for structured algebraic specification.
Two different but equivalent denotational semantics for Clear are
given. One is a version of a semantics due to Burstall and Goguen
with a few corrections, in which the category-theoretic notion of a
colimit is used to define Clear's structuring operations
independently of the underlying 'institution' (logical formalism).
The other semantics defines the same operations by means of
straightforward set-theoretic constructions; it is not institutionindependent
but it can be modified to handle all institutions of
apparent interest.
Both versions of the semantics have been implemented. The settheoretic
implementation is by far the more useful of the two, and
includes a parser and typechecker. An implementation is useful for
detecting syntax and type errors in specifications, and can be used
as a front end for systems which manipulate specifications. Several
large specifications which have been processed by the set-theoretic
implementation are presented.
A semi-automatic theorem prover for Clear built on top of the
Edinburgh LCF system is described. It takes advantage of the
structure of Clear specifications to restrict the available
information to that which seems relevant to proving the theorem at
hand. If the system is unable to prove a theorem automatically the
user can attempt the proof interactively using the high-level
primitives and inference rules provided.
We lay a theoretical foundation for the use of Clear in
systematic program development by investigating a new notion of the
implementation of a specification by a lower-level specification.
This notion extends to handle parameterised specifications. We show
that this implementation relation is transitive and commutes with
Clear's structuring operations under certain conditions. This means
that a large specification can be refined to a program in a gradual
and modular fashion, where the correctness of the individual
refinements guarantees the correctness of the resulting program
Theorem Provers as Libraries -- An Approach to Formally Verifying Functional Programs
Property-directed verification of functional programs tends to take one of two paths. First, is the traditional testing approach, where properties are expressed in the original programming language and checked with a collection of test data. Alternatively, for those desiring a more rigorous approach, properties can be written and checked with a formal tool; typically, an external proof system. This dissertation details a hybrid approach that captures the best of both worlds: the formality of a proof system paired with the native integration of an embedded, domain specific language (EDSL) for testing. At the heart of this hybridization is the titular concept -- a theorem prover as a library. The verification capabilities of this prover, HaskHOL, are introduced to a Haskell development environment as a GHC compiler plugin. Operating at the compiler level provides for a comparatively simpler integration and allows verification to co-exist with the numerous other passes that stand between source code and program
Fifty years of Hoare's Logic
We present a history of Hoare's logic.Comment: 79 pages. To appear in Formal Aspects of Computin
Peer Review of a Formal Verification/Design Proof Methodology
The role of formal verification techniques in system validation was examined. The value and the state of the art of performance proving for fault-tolerant compuers were assessed. The investigation, development, and evaluation of performance proving tools were reviewed. The technical issues related to proof methodologies are examined. The technical issues discussed are summarized
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