Using Dynamic Aspects in Music Composition Systems

Aspect-oriented programming (AOP) attempts to modularise crosscutting concerns in software. Initial approaches to AOP have used static weaving techniques in which crosscutting implementation, encapsulated by aspects, is merged into . Research into dynamic aspects suggests various ways in which crosscutting implementations may be dynamically woven into code, enabling aspects to be defined and composed at run-time. It has been suggested, in [14], that AOP might be usefully applied at the end-user level in applications that support multidimensional creative processes, and in particular, of music composition. In this paper we extend this argument to suggest that dynamic aspects are essential to this application. We motivate our argument with a high-level description of crosscutting that exists within music composition, and ways in which these crosscutting concerns, and requirements for their management, have arisen from our initial use of static aspects in music composition. We then evaluate some of the ways in which current research into dynamic aspects might be utilised in addressing these requirements

A Case for Custom, Composable Composition Operators

Programming languages typically support a fixed set of com- position operators, with fixed semantics. This may impose limits on software designers, in case a desired operator or semantics are not supported by a language, resulting in suboptimal quality characteristics of the designed software system. We demonstrate this using the well-known State design pattern, and propose the use of a composition infrastructure that allows the designer to define custom, composable composition operators. We demonstrate how this approach improves several quality factors of the State design pattern, such as reusability and modularity, while taking a reason- able amount of effort to define the necessary pattern-related code

Object-Centric Reflection: Unifying Reflection and Bringing It Back to Objects

Reflective applications are able to query and manipulate the structure and behavior of a running system. This is essential for highly dynamic software that needs to interact with objects whose structure and behavior are not known when the application is written. Software analysis tools, like debuggers, are a typical example. Oddly, although reflection essentially concerns run-time entities, reflective applications tend to focus on static abstractions, like classes and methods, rather than objects. This is phenomenon we call the object paradox, which makes developers less effective by drawing their attention away from run-time objects. To counteract this phenomenon, we propose a purely object-centric approach to reflection. Reflective mechanisms provide object-specific capabilities as another feature. Object-centric reflection proposes to turn this around and put object-specific capabilities as the central reflection mechanism. This change in the reflection architecture allows a unification of various reflection mechanisms and a solution to the object paradox. We introduce Bifr\"ost, an object-centric reflective system based on first-class meta-objects. Through a series of practical examples we demonstrate how object-centric reflection mitigates the object paradox by avoiding the need to reflect on static abstractions. We survey existing approaches to reflection to establish key requirements in the domain, and we show that an object-centric approach simplifies the meta-level and allows a unification of the reflection field. We demonstrate how development itself is enhanced with this new approach: talents are dynamically composable units of reuse, and object-centric debugging prevents the object paradox when debugging. We also demonstrate how software analysis is benefited by object-centric reflection with Chameleon, a framework for building object-centric analysis tools and MetaSpy, a domain-specific profile

First-class Compositions - Defining and composing object and aspect compositions with first-class operators

A considerable amount of research, especially within the OO and AOSD communities, has focused on understanding the potential and limitations of various composition techniques. This has led to a large number of proposals for alternative composition techniques, including many variations of message dispatch, inheritance, and aspect mechanisms. This paper makes the case that there is no single perfect composition technique that suits every situation, since different techniques incur different trade-offs. The proper composition technique to use depends on the particular design problem and its requirements (e.g., with respect to adaptability, reusability, understandability, robustness, etc. of the various elements of the design). However, most programming languages limit the available composition techniques to a very few. To address this, we propose a novel composition model, called Co-op. The model provides dedicated abstractions that can be used to express a wide variety of object composition techniques ("composition operators''). Examples include various forms of inheritance, delegation, and aspects. The proposed model unifies objects (with encapsulated state and a message interface) and composition operators; composition operators are specified as first-class citizens. Multiple composition operators can be combined within the same application, and composition operators can even be used to compose new composition operators from existing ones. This opens new possibilities for developing domain-specific composition operators, taxonomies of composition operators, and for reuse and refinement of composition operators. To validate and experiment with the proposed model, we have designed and implemented a simple language, Co-op/I, that we also use in this paper to show concrete examples

Open meta-modelling frameworks via meta-object protocols

Meta-modelling is central to Model-Driven Engineering. Many meta-modelling notations, approaches and tools have been proposed along the years, which widely vary regarding their supported modelling features. However, current approaches tend to be closed and rigid with respect to the supported concepts and semantics. Moreover, extending the environment with features beyond those natively supported requires highly technical knowledge. This situation hampers flexibility and interoperability of meta-modelling environments. In order to alleviate this situation, we propose open meta-modelling frameworks, which can be extended and configured via meta-object protocols (MOPs). Such environments offer extension points on events like element instantiation, model loading or property access, and enable selecting particular model elements over which the extensions are to be executed. We show how MOP-based mechanisms permit extending meta-modelling frameworks in a flexible way, and allow describing a wide range of meta-modelling concepts. As a proof of concept, we show and compare an implementation in the MetaDepth tool and an aspect-based implementation atop the Eclipse Modelling Framework (EMF). We have evaluated our approach by extending EMF and MetaDepth with modelling services not foreseen initially when they were created. The evaluation shows that MOP-based mechanisms permit extending meta-modelling frameworks in a flexible way, and are powerful enough to support the specification of a broad variety of meta-modelling featuresWork partially funded by projects RECOM and FLEXOR (Spanish MINECO,TIN2015-73968-JIN (AEI/FEDER/UE) and TIN2014-52129-R) and the R&D programme of the Madrid Region (S2013/ICE-3006

Runtime aspect weaving through metaprogramming

technical reportWe describe an extension to the Java language, Handi-Wrap, that supports weaving aspects into code at runtime. Aspects in Handi-Wrap take the form of method wrappers, which allow aspect code to be inserted around method bodies like advice in AspectJ. Handi- Wrap offers several advantages over static aspect languages such as AspectJ. First, aspects can be woven into binary libraries. Second, a wrapper in Handi-Wrap is a first-class Java value, which allows users to exploit Java mechanisms to define and weave wrappers. For example, wrappers can be passed explicit constructor arguments, and wrapper objects can be composed. Finally, methods in all Java classes, including anonymous classes, can be wrapped. A prototype of Handi-Wrap is implemented in a compile-time metaprogramming system for Java, called Maya; we briefly describe how Maya?s features support Handi- Wrap