Composition Of Design Patterns Research Articles

On the non-modular design of on-the-fly computations

On-the-fly computations are apparent in all levels of the CS studies. Yet, textbooks do not underline their characterizing design features. One of their primary features is the non-modular composition of design patterns. Additional design features involve insightful observations and the perspective of state transitions. Unfortunately, novices demonstrate limited competence with these features, even after repeatedly seeing on-the-fly designs. The objective of this paper is to shed light on the novice difficulties, and to elaborate on the above features, in advocating the importance of their explicit presentation to students.

CANON in D(esign): Composing scales of plant canopies from phytomers to whole-plants using the composite design pattern

Understanding plant development and architecture has been aided by the phytomer concept. The phytomer, usually considered a vegetative unit of a leaf, node, internode, axillary bud, and occasionally nodal roots, has been extended to the inflorescence with units repeated within and among shoots. For many reasons including insufficient knowledge of phytomer dynamics or specific modelling objectives, crop models may not fully incorporate phytomer concepts. For instance, commonly, some phytomers are aggregated into a single component such as an inflorescence component. Continuing development and maturing of object-oriented (OO) design provides opportunities for better representing phytomer concepts in crop models and integrating approaches using varying scales of resolution. Use of the structural Composite Design Pattern (CDP) in an OO plant design facilitates combining scales with a mixture of single and aggregated phytomers for different components. This paper uses winter wheat ( Triticum aestivum L.) to (1) illustrate building the entire plant canopy by the appearance, growth, and death of phytomer units, (2) translate this botanical abstraction into an OO design using the CDP, (3) use the CDP to facilitate a mixture of scales, and (4) present results of a proof-of-concept prototype, CANON, named because the interplay of repeating phytomers is analogous to the repeating melodies of a canon musical composition. CANON implements the phytomer concept of an entire canopy (both vegetative and reproductive phytomers) into an OO design using the CDP. This pattern facilitated the combination of simulation scales from individual reproductive phytomers to an aggregated inflorescence. Quantification of phytomer concepts for winter wheat was primarily derived from the SHOOTGRO model, with the addition of a simple aggregated inflorescence sub-model derived from the APSIM model. The CANON prototype was able to simulate the appearance, growth, and senescence of phytomers on individual shoots of the plant comprising the plant canopy. Importantly, CANON was able to incorporate legacy code with a lower scale of resolution than the phytomer. CANON demonstrates an OO design to simulate plant canopy development and growth from the sub-phytomer to whole-plant level, allowing flexibility in meeting different model objectives and available knowledge of processes.

Interleaved pattern composition and scaffolded learning

One of the essential skills required in the design of computer programs is the composition of design patterns in an interleaved way. We expect both beginners and senior students to demonstrate competence with this skill. Are they competent? Not quite. We found that both novices and seniors demonstrate disturbing difficulties with interleaved pattern composition. In order to address these difficulties, we developed a scaffolding instruction approach, which we applied with students. We display our findings, our approach, and the approach implementation.

A hierarchical component model for large parallel interactive applications

This paper focuses on parallel interactive applications ranging from scientific visualization, to virtual reality or computational steering. Interactivity makes them particular on three main aspects: they are endlessly iterative, use advanced I/O devices, and must perform under strong performance constraints (latency, refresh rate). A data flow graph is a common approach to describe such applications. Edges represent data streams while vertices are nodes processing incoming data streams and producing new data streams. When applications become large, this approach shows its limits in terms of maintainability and portability. In this paper, we propose to use the composite design pattern to extend this model for supporting hierarchies of components. The component hierarchy is traversed to instantiate the application and extract the data flow graph required for the execution. This approach has been implemented for the FlowVR middleware. It enables to define parametric composite components, commonly called skeletons, that can be reused in various applications. This approach proved to significantly leverage application modularity as presented in different case studies.

Composing pattern-based components and verifying correctness

Designing large software systems out of reusable components has become increasingly popular. Although liberal composition of reusable components saves time and expense, many experiments indicate that people will pay for this (liberal composition) sooner or later, sometimes paying even a higher price than the savings obtained from reusing components. Thus, we advocate that more rigorous analysis methods to check the correctness of component composition would allow combination problems to be detected early in the development process so that people can save the considerable effort of fixing errors downstream. In this paper we describe a rigorous method for component composition that can be used to solve combination and integration problems at the (architectural) design phase of the software development lifecycle. In addition, we introduce the notion of composition pattern in order to promote the reuse of composition solutions to solve routine component composition problems. Once a composition pattern is proven correct, its instances can be used in a particular application without further proof. In this way, our proposed method involves reusing compositions as well as reusing components. We illustrate our approach through an example related to the composition of design patterns as design components. Structural and behavioral correctness proofs about the composition of design patterns are provided. Case studies are also presented to show the applications of the composition patterns.

Expression and Composition of Design Patterns with AspectJ

Design patterns are well-known couples of problems-solutions for software engineer- ing. By nature, they often lack support from languages and this further complicates the study of their composition in the code. Aspect-oriented languages provide new mechanisms for modula- rization, which can help to improve design patterns implementation. (Hannemann et al., 2002) is the first extensive study of patterns aspectization with AspectJ. We notice some AspectJ idioms are needed in order to implement object relationships. We give a more reusable VISITOR pat- tern. We highlight a reusable composition of COMPOSITE and VISITOR patterns and expressive interactions of the OBSERVER pattern with a tree structure. We thus show that modularization by aspects helps composition of design patterns.

Formalising design patterns composition

A design pattern describes a set of proven solutions to a recurring problem within a context. Most design patterns are specified in an informal fashion, which can give rise to ambiguity that may lead to incorrect usage. Thus, reasoning about them requires formalisation. Balanced Pattern Specification Language (BPSL) was developed in order to formally specify the structural as well as behavioural aspects of patterns. When designing software, in most cases two or more patterns are to be composed to solve a bigger problem. In this sense patterns represent micro-architectures that when glued together could create an entire software architecture. Thus, if formalised, pattern composition can lead to ready-made architectures from which only instantiation would be required to build robust implementations. This paper focuses mainly on BPSL's rigorous pattern composition process using the Observer-Mediator pattern composition as a case study.

Software Framework Concepts for Power Distribution System Analysis

Software design reuse has been discussed in the past at the component level through Design Patterns. A software framework is an approach to achieve software reusability for an entire domain. This paper presents architectural design concepts of a framework for power distribution system analysis. The commonalities of distribution system analysis, including components, topologies, and algorithms are considered. A layered architecture with strict top-down dependency is proposed to decrease software couplings. Interfaces are used to hide the internal structure of each layer. The Composite and Iterator design patterns are used in the framework design. This paper also presents practical examples of developing customized applications that reuse and extend the framework.

Rapid software prototyping in molecular modeling using the biochemical algorithms library (BALL)

In the next century, virtual laboratories will play a key role in biotechnology. Computer experiments will not only replace some of the time-consuming and expensive real-world experiments, but they will also provide insights that cannot be obtained using "wet" experiments. The field that deals with the modeling of atoms, molecules, and their reactions is called Molecular Modeling. The advent of Life Sciences gave rise to numerous new developments in this area. However, the implementation of new simulation tools is extremely time-consuming. This is mainly due to the large amount of supporting code that is required in addition to the code necessary to implement the new idea. The only way to reduce the development time is to reuse reliable code, preferably using object-oriented approaches. We have designed and implemented BALL, the first object-oriented application framework for rapid prototyping in Molecular Modeling. By the use of the composite design pattern and polymorphism we were able to model the multitude of complex biochemical concepts in a well-structured and comprehensible class hierarchy, the BALL kernel classes. The isomorphism between the biochemical structures and the kernel classes leads to an intuitive interface. Since BALL was designed for rapid software prototyping, ease of use, extensibility, and robustness were our principal design goals. Besides the kernel classes, BALL provides fundamental components for import/export of data in various file formats, Molecular Mechanics simulations, three-dimensional visualization, and more complex ones like a numerical solver for the Poisson-Boltzmann equation.

Composite design patterns

Software design patterns are the core abstractions from successful recurring problem solutions in software design. Composite design patterns are the core abstractions from successful recurring frameworks. A composite design pattern is a pattern that is best described as the composition of further patterns the integration of which shows a synergy that makes the composition more than just the sum of its parts. This paper presents examples of composite patterns, discusses a role-based analysis and composition technique, and demonstrates that composite patterns extend the pattern idea from single problem solutions to object-oriented frameworks.