274 research outputs found
A Data Transformation System for Biological Data Sources
Scientific data of importance to biologists in the Human Genome Project resides not only in conventional databases, but in structured files maintained in a number of different formats (e.g. ASN.1 and ACE) as well a.s sequence analysis packages (e.g. BLAST and FASTA). These formats and packages contain a number of data types not found in conventional databases, such as lists and variants, and may be deeply nested. We present in this paper techniques for querying and transforming such data, and illustrate their use in a prototype system developed in conjunction with the Human Genome Center for Chromosome 22. We also describe optimizations performed by the system, a crucial issue for bulk data
Relational Parametricity for Computational Effects
According to Strachey, a polymorphic program is parametric if it applies a
uniform algorithm independently of the type instantiations at which it is
applied. The notion of relational parametricity, introduced by Reynolds, is one
possible mathematical formulation of this idea. Relational parametricity
provides a powerful tool for establishing data abstraction properties, proving
equivalences of datatypes, and establishing equalities of programs. Such
properties have been well studied in a pure functional setting. Many programs,
however, exhibit computational effects, and are not accounted for by the
standard theory of relational parametricity. In this paper, we develop a
foundational framework for extending the notion of relational parametricity to
programming languages with effects.Comment: 31 pages, appears in Logical Methods in Computer Scienc
Facilitating modular property-preserving extensions of programming languages
We will explore an approach to modular programming language descriptions and extensions in a denotational style.
Based on a language core, language features are added stepwise on the core. Language features can be described
separated from each other in a self-contained, orthogonal way. We present an extension semantics framework consisting
of mechanisms to adapt semantics of a basic language to new structural requirements in an extended language
preserving the behaviour of programs of the basic language. Common templates of extension are provided. These
can be collected in extension libraries accessible to and extendible by language designers. Mechanisms to extend
these libraries are provided. A notation for describing language features embedding these semantics extensions is
presented
Coinductive Resumption Monads: Guarded Iterative and Guarded Elgot
We introduce a new notion of "guarded Elgot monad", that is a monad equipped with a form of iteration. It requires every guarded morphism to have a specified fixpoint, and classical equational laws of iteration to be satisfied. This notion includes Elgot monads, but also further examples of partial non-unique iteration, emerging in the semantics of processes under infinite trace equivalence.
We recall the construction of the "coinductive resumption monad" from a monad and endofunctor, that is used for modelling programs up to bisimilarity. We characterize this construction via a universal property: if the given monad is guarded Elgot, then the coinductive resumption monad is the guarded Elgot monad that freely extends it by the given endofunctor
Lifting homotopy T-algebra maps to strict maps
The settings for homotopical algebra---categories such as simplicial groups,
simplicial rings, spaces, ring spectra, etc.---are often
equivalent to categories of algebras over some monad or triple . In such
cases, is acting on a nice simplicial model category in such a way that
descends to a monad on the homotopy category and defines a category of homotopy
-algebras. In this setting there is a forgetful functor from the homotopy
category of -algebras to the category of homotopy -algebras.
Under suitable hypotheses we provide an obstruction theory, in the form of a
Bousfield-Kan spectral sequence, for lifting a homotopy -algebra map to a
strict map of -algebras. Once we have a map of -algebras to serve as a
basepoint, the spectral sequence computes the homotopy groups of the space of
-algebra maps and the edge homomorphism on is the aforementioned
forgetful functor. We discuss a variety of settings in which the required
hypotheses are satisfied, including monads arising from algebraic theories and
operads. We also give sufficient conditions for the -term to be calculable
in terms of Quillen cohomology groups.
We provide worked examples in -spaces, -spectra, rational
algebras, and algebras. Explicit calculations, connected to rational
unstable homotopy theory, show that the forgetful functor from the homotopy
category of ring spectra to the category of ring spectra
is generally neither full nor faithful. We also apply a result of the second
named author and Nick Kuhn to compute the homotopy type of the space
.Comment: 45 pages. Substantial revision. To appear in Advances in Mathematic
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