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OrderSorted Algebra I: Equational Deduction for Multiple Inheritance, Overloading, Exceptions and Partial Operations
 Theoretical Computer Science
, 1992
"... This paper generalizes manysorted algebra (hereafter, MSA) to ordersorted algebra (hereafter, OSA) by allowing a partial ordering relation on the set of sorts. This supports abstract data types with multiple inheritance (in roughly the sense of objectoriented programming), several forms of pol ..."
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Cited by 208 (33 self)
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This paper generalizes manysorted algebra (hereafter, MSA) to ordersorted algebra (hereafter, OSA) by allowing a partial ordering relation on the set of sorts. This supports abstract data types with multiple inheritance (in roughly the sense of objectoriented programming), several forms of polymorphism and overloading, partial operations (as total on equationally defined subsorts), exception handling, and an operational semantics based on term rewriting. We give the basic algebraic constructions for OSA, including quotient, image, product and term algebra, and we prove their basic properties, including Quotient, Homomorphism, and Initiality Theorems. The paper's major mathematical results include a notion of OSA deduction, a Completeness Theorem for it, and an OSA Birkhoff Variety Theorem. We also develop conditional OSA, including Initiality, Completeness, and McKinseyMalcev Quasivariety Theorems, and we reduce OSA to (conditional) MSA, which allows lifting many known MSA results to OSA. Retracts, which intuitively are left inverses to subsort inclusions, provide relatively inexpensive runtime error handling. We show that it is safe to add retracts to any OSA signature, in the sense that it gives rise to a conservative extension. A final section compares and contrasts many different approaches to OSA. This paper also includes several examples demonstrating the flexibility and applicability of OSA, including some standard benchmarks like STACK and LIST, as well as a much more substantial example, the number hierarchy from the naturals up to the quaternions.
Completion of Rewrite Systems with Membership Constraints Part II: Constraint Solving
 J. Symbolic Computation
, 1992
"... this paper is to show how to solve the constraints that are involved in the deduction mechanism of the first part. This may be interesting in its own since this provides with a unification algorithm for an ordersorted logic with context variables and can be read independently of the first part. Thi ..."
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Cited by 66 (2 self)
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this paper is to show how to solve the constraints that are involved in the deduction mechanism of the first part. This may be interesting in its own since this provides with a unification algorithm for an ordersorted logic with context variables and can be read independently of the first part. This can also be compared with unification of term schemes of various kind (Chen & Hsiang, 1991; Salzer, 1992; Comon, 1995; R. Galbav'y and M. Hermann, 1992). Indeed,
Building Equational Proving Tools by Reflection in Rewriting Logic
 In Cafe: An IndustrialStrength Algebraic Formal Method
, 1998
"... This paper explains the design and use of two equational proving tools, namely an inductive theorem prover  to prove theorems about equational specifications with an initial algebra semantics  and a ChurchRosser checkerto check whether such specifications satisfy the ChurchRosser property. ..."
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Cited by 38 (19 self)
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This paper explains the design and use of two equational proving tools, namely an inductive theorem prover  to prove theorems about equational specifications with an initial algebra semantics  and a ChurchRosser checkerto check whether such specifications satisfy the ChurchRosser property. These tools can be used to prove properties of ordersorted equational specifications in Cafe [11] and of membership equational logic specifications in Maude [7, 6]. The tools have been written entirely in Maude and are in fact executable specifications in rewriting logic of the formal inference systems that they implement.
A Core Language for Rewriting
 Electronic Notes in Theoretical Computer Science
, 1998
"... System S is a calculus providing the basic abstractions of term rewriting: matching and building terms, term traversal, combining computations and handling failure. The calculus forms a core language for implementation of a wide variety of rewriting languages, or more generally, languages for specif ..."
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Cited by 24 (8 self)
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System S is a calculus providing the basic abstractions of term rewriting: matching and building terms, term traversal, combining computations and handling failure. The calculus forms a core language for implementation of a wide variety of rewriting languages, or more generally, languages for specifying tree transformations. In this paper we showhow a conventional rewriting language based on conditional term rewriting can be implemented straightforwardly in System S. Subsequently we show how this implementation can be extended with features such as matching conditions, negative conditions, default rules, nonstrictness annotations and alternativeevaluation strategies. 1 Introduction Term rewriting is a theoretically wellde#ned paradigm that consists of reducing a term to normal form with respect to a set of rewrite rules #12,5,1#. However, in practical instantiations of this paradigm a wide variety of features are added to this basic paradigm. This has resulted in the design and impl...
Operational termination of membership equational programs. the ordersorted way
, 2008
"... Our main goal is automating termination proofs for programs in rewritingbased languages with features such as: (i) expressive type structures, (ii) conditional rules, (iii) matching modulo axioms, and (iv) contextsensitive rewriting. Specifically, we present a new operational termination method for ..."
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Cited by 21 (9 self)
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Our main goal is automating termination proofs for programs in rewritingbased languages with features such as: (i) expressive type structures, (ii) conditional rules, (iii) matching modulo axioms, and (iv) contextsensitive rewriting. Specifically, we present a new operational termination method for membership equational programs with features (i)(iv) that can be applied to programs in membership equational logic (MEL). The method first transforms a MEL program into a simpler, yet semantically equivalent, conditional ordersorted (OS) program. Subsequent trasformations make the OSprogram unconditonal, and, finally, unsorted. In particular, we extend and generalize to this richer setting an ordersorted termination technique for unconditional OS programs proposed by Ölveczky and Lysne. An important advantage of our method is that it minimizes the use of conditional rules and produces simpler transformed programs whose termination is often easier to prove automatically.
A Logical Semantics for ObjectOriented Databases
 In Proc. International SIGMOD Conference on Management of Data
, 1993
"... Although the mathematical foundations of relational databases are very well established, the state of affairs for objectoriented databases is much less satisfactory. We propose a semantic foundation for objectoriented databases based on a simple logic of change called rewriting logic, and a langua ..."
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Cited by 19 (2 self)
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Although the mathematical foundations of relational databases are very well established, the state of affairs for objectoriented databases is much less satisfactory. We propose a semantic foundation for objectoriented databases based on a simple logic of change called rewriting logic, and a language called MaudeLog that is based on that logic. Some key advantages of our approach include its logical nature, its simplicity without any need for higherorder features, the fact that dynamic aspects are directly addressed, the rigorous integration of userdefinable algebraic data types within the framework, the existence of initial models, and the integration of query, update, and programming aspects within a single declarative language. 1 Introduction Although the mathematical foundations of relational databases are very well established, the state of affairs for objectoriented databases is much less satisfactory. This is unfortunate, because objectoriented databases seem to have impor...
How to Transform Canonical Decreasing CTRSs into Equivalent Canonical TRSs
 In Proceedings of the 4th International Workshop on Conditional Term Rewriting Systems
, 1994
"... We prove constructively that the class of groundconfluent and decreasing conditional term rewriting systems (CTRSs) (without extra variables) coincides with the class of orthogonal and terminating, unconditional term rewriting systems (TRSs). TRSs being included in CTRSs, this result follows from a ..."
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Cited by 9 (0 self)
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We prove constructively that the class of groundconfluent and decreasing conditional term rewriting systems (CTRSs) (without extra variables) coincides with the class of orthogonal and terminating, unconditional term rewriting systems (TRSs). TRSs being included in CTRSs, this result follows from a transformation from any groundconfluent and decreasing CTRS specifying a computable function f into a TRS with the mentioned properties for f . The generated TRS is ordersorted, but we outline a similar transformation yielding an unsorted TRS.
Termination Modulo Combinations of Equational Theories
"... Abstract. Rewriting with rules R modulo axioms E is a widely used technique in both rulebased programming languages and in automated deduction. Termination methods for rewriting systems modulo specific axioms E (e.g., associativitycommutativity) are known. However, much less seems to be known abou ..."
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Cited by 6 (5 self)
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Abstract. Rewriting with rules R modulo axioms E is a widely used technique in both rulebased programming languages and in automated deduction. Termination methods for rewriting systems modulo specific axioms E (e.g., associativitycommutativity) are known. However, much less seems to be known about termination methods that can be modular in the set E of axioms. In fact, current termination tools and proof methods cannot be applied to commonly occurring combinations of axioms that fall outside their scope. This work proposes a modular termination proof method based on semantics and terminationpreserving transformations that can reduce the proof of termination of rules R modulo E to an equivalent proof of termination of the transformed rules modulo a typically much simpler set B of axioms. Our method is based on the notion of variants of a term recently proposed by Comon and Delaune. We illustrate its practical usefulness by considering the very common case in which E is an arbitrary combination of associativity, commutativity, left and rightidentity axioms for various function symbols. 1
Stretching First Order Equational Logic: Proofs with Partiality, Subtypes and Retracts
 Proceedings, Workshop on First Order Theorem Proving
, 1998
"... It is widely recognized that equational logic is simple, (relatively) decidable, and (relatively) easily mechanized. But it is also widely thought that equational logic has limited applicability because it cannot handle subtypes or partial functions. We show that a modest stretch of equational logic ..."
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Cited by 5 (2 self)
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It is widely recognized that equational logic is simple, (relatively) decidable, and (relatively) easily mechanized. But it is also widely thought that equational logic has limited applicability because it cannot handle subtypes or partial functions. We show that a modest stretch of equational logic effectively handles these features. Space limits preclude a full theoretical treatment, so we often sketch, motivate and exemplify.