EOOLT 2007 – Proceedings of the 1st International Workshop on Equation-Based Object-Oriented Languages and Tools

Computer aided modeling and simulation of complex systems, using components from multiple application domains, such as electrical, mechanical, hydraulic, control, etc., have in recent years witness0065d a significant growth of interest. In the last decade, novel equation-based object-oriented (EOO) modeling languages, (e.g. Mode- lica, gPROMS, and VHDL-AMS) based on acausal modeling using equations have appeared. Using such languages, it has become possible to model complex systems covering multiple application domains at a high level of abstraction through reusable model components. The interest in EOO languages and tools is rapidly growing in the industry because of their increasing importance in modeling, simulation, and specification of complex systems. There exist several different EOO language communities today that grew out of different application areas (multi-body system dynamics, electronic circuit simula- tion, chemical process engineering). The members of these disparate communities rarely talk to each other in spite of the similarities of their modeling and simulation needs. The EOOLT workshop series aims at bringing these different communities together to discuss their common needs and goals as well as the algorithms and tools that best support them. Despite the short deadlines and the fact that this is a new not very established workshop series, there was a good response to the call-for-papers. Thirteen papers and one presentation were accepted to the workshop program. All papers were subject to reviews by the program committee, and are present in these electronic proceedings. The workshop program started with a welcome and introduction to the area of equa- tion-based object-oriented languages, followed by paper presentations and discussion sessions after presentations of each set of related papers. On behalf of the program committee, the Program Chairmen would like to thank all those who submitted papers to EOOLT'2007. Special thanks go to David Broman who created the web page and helped with organization of the workshop. Many thanks to the program committee for reviewing the papers. EOOLT'2007 was hosted by the Technical University of Berlin, in conjunction with the ECOOP'2007 conference

A SAT-based System for Consistent Query Answering

An inconsistent database is a database that violates one or more integrity constraints, such as functional dependencies. Consistent Query Answering is a rigorous and principled approach to the semantics of queries posed against inconsistent databases. The consistent answers to a query on an inconsistent database is the intersection of the answers to the query on every repair, i.e., on every consistent database that differs from the given inconsistent one in a minimal way. Computing the consistent answers of a fixed conjunctive query on a given inconsistent database can be a coNP-hard problem, even though every fixed conjunctive query is efficiently computable on a given consistent database. We designed, implemented, and evaluated CAvSAT, a SAT-based system for consistent query answering. CAvSAT leverages a set of natural reductions from the complement of consistent query answering to SAT and to Weighted MaxSAT. The system is capable of handling unions of conjunctive queries and arbitrary denial constraints, which include functional dependencies as a special case. We report results from experiments evaluating CAvSAT on both synthetic and real-world databases. These results provide evidence that a SAT-based approach can give rise to a comprehensive and scalable system for consistent query answering.Comment: 25 pages including appendix, to appear in the 22nd International Conference on Theory and Applications of Satisfiability Testin

Constraint Functional Logic Programming over Finite Domains.

Abstract In this paper, we present our proposal to Constraint Functional Logic Programming over Finite Domains (CFLP (FD) ) with a lazy functional logic programming language which seamlessly embodies finite domain (FD) constraints. This proposal increases the expressiveness and power of constraint logic programming over finite domains (CLP (FD) ) by combining functional and relational notation, curried expressions, higher-order functions, patterns, partial applications, non-determinism, lazy evaluation, logical variables, types, domain variables, constraint composition, and finite domain constraints. We describe the syntax of the language, its type discipline, and its declarative and operational semantics. We also describe TOY(FD), an implementation for CFLP (FD) , and a comparison of our approach with respect to CLP (FD) from a programming point of view, showing the new features we introduce. And, finally, we show a performance analysis which demonstrates that our implementation is competitive with respect to existing CLP (FD) systems and that clearly outperforms the closer approach to CFLP (FD)

Semantic methods for functional hybrid modelling

Equation-based modelling languages have become a vital tool in many areas of science and engineering. Functional Hybrid Modelling (FHM) is an approach to equation-based modelling that allows the behaviour of a physical system to be expressed as a modular hierarchy of undirected equations. FHM supports a variety of advanced language features — such as higher-order models and variable system structure — that sets it apart from the majority of other modelling languages. However, the inception of these new features has not been accompanied by the semantic tools required to effectively use and understand them. Specifically, there is a lack of static safety assurances for dynamic models and the semantics of the aforementioned language features are poorly understood. Static safety guarantees are highly desirable as they allow problems that may cause an equation system to become unsolvable to be detected early, during compilation. As a result, the use of static analysis techniques to enforce structural invariants (e.g. that there are the same number of equations as unknowns) is now in use in main-stream equation-based languages like Modelica. Unfortunately, the techniques employed by these languages are somewhat limited, both in their capacity to deal with advanced language features and also by the spectrum of invariants they are able to enforce. Formalising the semantics of equation-based languages is also important. Semantics allow us to better understand what a program is doing during execution, and to prove that this behaviour meets with our expectation. They also allow different implementations of a language to agree with one another, and can be used to demonstrate the correctness of a compiler or interpreter. However, current attempts to formalise such semantics typically fall short of describing advanced features, are not compositional, and/or fail to show correctness. This thesis provides two major contributions to equation-based languages. Firstly, we develop a refined type system for FHM capable of capturing a larger number of structural anomalies than is currently possible with existing methods. Secondly, we construct a compositional semantics for the discrete aspects of FHM, and prove a number of key correctness properties

Semantic methods for functional hybrid modelling

Equation-based modelling languages have become a vital tool in many areas of science and engineering. Functional Hybrid Modelling (FHM) is an approach to equation-based modelling that allows the behaviour of a physical system to be expressed as a modular hierarchy of undirected equations. FHM supports a variety of advanced language features — such as higher-order models and variable system structure — that sets it apart from the majority of other modelling languages. However, the inception of these new features has not been accompanied by the semantic tools required to effectively use and understand them. Specifically, there is a lack of static safety assurances for dynamic models and the semantics of the aforementioned language features are poorly understood. Static safety guarantees are highly desirable as they allow problems that may cause an equation system to become unsolvable to be detected early, during compilation. As a result, the use of static analysis techniques to enforce structural invariants (e.g. that there are the same number of equations as unknowns) is now in use in main-stream equation-based languages like Modelica. Unfortunately, the techniques employed by these languages are somewhat limited, both in their capacity to deal with advanced language features and also by the spectrum of invariants they are able to enforce. Formalising the semantics of equation-based languages is also important. Semantics allow us to better understand what a program is doing during execution, and to prove that this behaviour meets with our expectation. They also allow different implementations of a language to agree with one another, and can be used to demonstrate the correctness of a compiler or interpreter. However, current attempts to formalise such semantics typically fall short of describing advanced features, are not compositional, and/or fail to show correctness. This thesis provides two major contributions to equation-based languages. Firstly, we develop a refined type system for FHM capable of capturing a larger number of structural anomalies than is currently possible with existing methods. Secondly, we construct a compositional semantics for the discrete aspects of FHM, and prove a number of key correctness properties

Characterising Renaming within OCaml’s Module System: Theory and Implementation

We present an abstract, set-theoretic denotational semantics for a significant subset of OCaml and its module system in order to reason about the correctness of renaming value bindings. Our abstract semantics captures information about the binding structure of programs. Crucially for renaming, it also captures information about the relatedness of different declarations that is induced by the use of various different language constructs (e.g. functors, module types and module constraints). Correct renamings are precisely those that preserve this structure. We demonstrate that our semantics allows us to prove various high-level, intuitive properties of renamings. We also show that it is sound with respect to a (domain-theoretic) denotational model of the operational behaviour of programs. This formal framework has been implemented in a prototype refactoring tool for OCaml that performs renamin

Mechanized Reasoning About how Using Functional Programs And Embeddings

Embedding describes the process of encoding a program\u27s syntax and/or semantics in another language---typically a theorem prover in the context of mechanized reasoning. Among different embedding styles, deep embeddings are generally preferred as they enable the most faithful modeling of the original language. However, deep embeddings are also the most complex, and working with them requires additional effort. In light of that, this dissertation aims to draw more attention to alternative styles, namely shallow and mixed embeddings, by studying their use in mechanized reasoning about programs\u27 properties that are related to how . More specifically, I present a simple shallow embedding for reasoning about computation costs of lazy programs, and a class of mixed embeddings that are useful for reasoning about properties of general computation patterns in effectful programs. I show the usefulness of these embedding styles with examples based on real-world applications