3,621 research outputs found
Bridging the gap between design and implementation of components libraries
Object-oriented design is usually driven by three main reusability principles:
step-by-step design, design for reuse and design with reuse. However, these
principles are just partially
applied to the subsequent object-oriented implementation, often due to efficienc
y
constraints, yielding to a gap between design and implementation. In this paper
we provide a solution for bridging this gap for a concrete framework, the one of
designing and implementing container-like component libraries, such as STL, Booc
h
Components, etc. Our approach is based on a new design pattern together with its
corresponding implementation. The proposal enhances the same principles that
drive the design process: step-by--step implementation (adding just what is
needed in every step), implementation with reuse (component implementations are
reused while library implementation
progresses and component hierarchies grow) and implementation for reuse
(intermediate component implementations can be reused in many different points o
f
the hierarchy). We use our approach in two different manners: for building a
brand-new container-like
component library, and for reengineering an existing one, Booch Components in
Ada95.Postprint (published version
Improving design and implementation of OO container-like component libraries
Object-oriented design is usually driven by three main reusability
principles: step-by-step design, design for reuse and design with reuse.
However, these principles tend to be just partially applied to the
subsequent object-oriented implementation, often because they conflict
with other quality criteria (remarkably, efficiency). So, there is a gap
between design and implementation: due to these conflicts developers use
to give up design level abstractions during the implementation. In this
paper we present a framework for bridging this gap for a concrete
domain, the design and implementation of object-oriented container-like
component libraries, such as JCF, STL, Booch Components, LEDA, etc. At
the core of the framework we propose a new design pattern called
emph{Shortcut} together with its corresponding implementation. The
Shortcut pattern, introduced in a generic base class container, provides
a secure and efficient access to items in a container decoupled from the
implementation details of concrete containers. Shortcut enhances
applying the same principles that drive the design process to the
implementation process of these libraries: step-by-step implementation,
implementation with reuse and implementation for reuse without
penalising other quality criteria. Our framework not only supports the
design and implementation of new libraries but also the reengineering of
existing ones to overcome some of their drawbacks. We show by a case
study, reengineering the Booch Components in Ada95, the application and
benefits of our framework.Postprint (published version
Adding efficient and reliable access paths to the JCF
The Java Collections Framework (JCF) is the standard Java library for
representing and manipulating collections (i.e., objects that represent
a group of objects, such as sets, lists, etc.). Although JCF provides
adequate functionality for many purposes, it does not offer any
mechanism for accessing directly the objects stored in collections
apart from the standard Java references. This absence is a crucial
functionality exhibited by many other widespread Java and non-Java
collection libraries. In this paper, we carry out a reengineering
process on the JCF to add this kind of alternative access paths, which
we give the name of shortcuts. This process relies on a framework
called Shortcut-Based Framework, which has been defined as library-
independent. We present this framework and then we show how it may be
tailored to the specific case of the JCF. The resulting JCF with
shortcuts library is fully compatible with the original one (i.e.,
programs using the original JCF are not required to be modified), and
exhibits good behaviour with respect to efficiency, reliability and
internal quality. As an additional benefit of the framework, we mention
that it can be applied to other collection libraries, as we have done
before with an Ada95 one.Postprint (published version
Shortcuts: abstract "pointers''
In this work we present the specification and the implementation
of a new abstract data type (ADT) called STORE. This new ADT allows
the storage of a given collection of elements offering an abstract
mechanism that supplies a direct access to them, alternative to the
method defined by the standard operations of usual ADTs. The interest
of the new mechanism stems from the efficiency of pointers, while
avoiding the loss of modularity that usually occurs when pointers
are used. The implementation of the operations offered by the new
ADT is done by derivation from the equational specification. The
representation chosen for the implementation of the new ADT makes
the efficiency previously mentioned possible, even when the
representation strategy requires the movement of the elements.Postprint (published version
Who Learns Better Bayesian Network Structures: Accuracy and Speed of Structure Learning Algorithms
Three classes of algorithms to learn the structure of Bayesian networks from
data are common in the literature: constraint-based algorithms, which use
conditional independence tests to learn the dependence structure of the data;
score-based algorithms, which use goodness-of-fit scores as objective functions
to maximise; and hybrid algorithms that combine both approaches.
Constraint-based and score-based algorithms have been shown to learn the same
structures when conditional independence and goodness of fit are both assessed
using entropy and the topological ordering of the network is known (Cowell,
2001).
In this paper, we investigate how these three classes of algorithms perform
outside the assumptions above in terms of speed and accuracy of network
reconstruction for both discrete and Gaussian Bayesian networks. We approach
this question by recognising that structure learning is defined by the
combination of a statistical criterion and an algorithm that determines how the
criterion is applied to the data. Removing the confounding effect of different
choices for the statistical criterion, we find using both simulated and
real-world complex data that constraint-based algorithms are often less
accurate than score-based algorithms, but are seldom faster (even at large
sample sizes); and that hybrid algorithms are neither faster nor more accurate
than constraint-based algorithms. This suggests that commonly held beliefs on
structure learning in the literature are strongly influenced by the choice of
particular statistical criteria rather than just by the properties of the
algorithms themselves.Comment: 27 pages, 8 figure
Nebrija, Cerezo y Sedeño como editores de los "Libri minores": tres actitudes filológicas diferentes
Ciberacoso: propuesta de intervención
Treball Final del Màster Universitari en Intervenció i Mediació Familiar (Pla de 2014). Codi: SBD016. Curs acadèmic 2014-201
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