6,939 research outputs found
Generic Ownership Types for Java and the Collections Framework
Generic programming has turned out very useful in the development of reusable software. With the Java programming language, genericity is not only meant for reusability, but also for type-safety. Java generics constrain a container object (e.g., list, hash table) to store objects of a pre-specified data type. Nevertheless, safe programming with aliasing (multiple pointers in a program may point to the same object) is still a concern in object-oriented programming language research. A pointing object can mutate the state of the aliased object, reflecting the changes to all of the other pointers (aka aliases) thus affecting their behaviour. As programs grow larger and more complex, such changes in behaviour can be undesirable and difficult to detect and reason about. With respect to container objects, the iterator pattern critically violates encapsulation, allowing aliases to the state (and thereof the components) of its container.
Object ownership is one of the well-researched paradigms in the area of alias management. Ownership types support hierarchical object encapsulation rather than the traditional class-level encapsulation. This thesis introduces an extension of Java 6 with support for ownership types as supplementary generic types. That is, Java generics are extended with the ability of carrying ownership information. This extension provides generic ownership support for all of Java; that is, all major language features are addressed so that programs can safely manage and express their aliasing properties. The resulting language is expressive enough to support common programming idioms, with little programming and runtime overhead. We evaluated the programmability of the language by refactoring a major (the most essential) portion of the Java Collections Framework. We also evaluated the performance impact of our refactoring by conducting a small micro-benchmark study to measure the performance time overhead the refactored collections may impose
Encapsulation and Aggregation
A notion of object ownership is introduced as a solution to difficult problems of specifying and reasoning about complex linked structures and of modeling aggregates (composit objects). Syntax and semantics are provided for extending Eiffel with language support for object ownership annotation and checking. The ideas also apply to other OOPLs such as C++
The C Object System: Using C as a High-Level Object-Oriented Language
The C Object System (Cos) is a small C library which implements high-level
concepts available in Clos, Objc and other object-oriented programming
languages: uniform object model (class, meta-class and property-metaclass),
generic functions, multi-methods, delegation, properties, exceptions, contracts
and closures. Cos relies on the programmable capabilities of the C programming
language to extend its syntax and to implement the aforementioned concepts as
first-class objects. Cos aims at satisfying several general principles like
simplicity, extensibility, reusability, efficiency and portability which are
rarely met in a single programming language. Its design is tuned to provide
efficient and portable implementation of message multi-dispatch and message
multi-forwarding which are the heart of code extensibility and reusability.
With COS features in hand, software should become as flexible and extensible as
with scripting languages and as efficient and portable as expected with C
programming. Likewise, Cos concepts should significantly simplify adaptive and
aspect-oriented programming as well as distributed and service-oriented
computingComment: 18
Extensible Component Based Architecture for FLASH, A Massively Parallel, Multiphysics Simulation Code
FLASH is a publicly available high performance application code which has
evolved into a modular, extensible software system from a collection of
unconnected legacy codes. FLASH has been successful because its capabilities
have been driven by the needs of scientific applications, without compromising
maintainability, performance, and usability. In its newest incarnation, FLASH3
consists of inter-operable modules that can be combined to generate different
applications. The FLASH architecture allows arbitrarily many alternative
implementations of its components to co-exist and interchange with each other,
resulting in greater flexibility. Further, a simple and elegant mechanism
exists for customization of code functionality without the need to modify the
core implementation of the source. A built-in unit test framework providing
verifiability, combined with a rigorous software maintenance process, allow the
code to operate simultaneously in the dual mode of production and development.
In this paper we describe the FLASH3 architecture, with emphasis on solutions
to the more challenging conflicts arising from solver complexity, portable
performance requirements, and legacy codes. We also include results from user
surveys conducted in 2005 and 2007, which highlight the success of the code.Comment: 33 pages, 7 figures; revised paper submitted to Parallel Computin
Capability Coordination in Modular Organization: Voluntary FS/OSS Production and the Case of Debian GNU/Linux
The paper analyzes voluntary Free Software/Open Source Software (FS/OSS) organization of work. The empirical setting considered is the Debian GNU/Linux operating system. The paper finds that the production process is hierarchical notwithstanding the modular (nearly decomposable) architecture of software and of voluntary FS/OSS organization. But voluntary FS/OSS project organization is not hierarchical for the same reasons suggested by the most familiar theories of economic organization: hierarchy is justified for coordination of continuous change, rather than for the direction of static production. Hierarchy is ultimately the overhead attached to the benefits engendered by modular organization.Modularity, hierarchy, capabilities, coordination costs, software.
Flexible Invariants Through Semantic Collaboration
Modular reasoning about class invariants is challenging in the presence of
dependencies among collaborating objects that need to maintain global
consistency. This paper presents semantic collaboration: a novel methodology to
specify and reason about class invariants of sequential object-oriented
programs, which models dependencies between collaborating objects by semantic
means. Combined with a simple ownership mechanism and useful default schemes,
semantic collaboration achieves the flexibility necessary to reason about
complicated inter-object dependencies but requires limited annotation burden
when applied to standard specification patterns. The methodology is implemented
in AutoProof, our program verifier for the Eiffel programming language (but it
is applicable to any language supporting some form of representation
invariants). An evaluation on several challenge problems proposed in the
literature demonstrates that it can handle a variety of idiomatic collaboration
patterns, and is more widely applicable than the existing invariant
methodologies.Comment: 22 page
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