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## Über dieses Buch

The LNCS journal Transactions on Aspect-Oriented Software Development is devoted to all facets of aspect-oriented software development (AOSD) techniques in the context of all phases of the software life cycle, from requirements and design to implementation, maintenance and evolution. The focus of the journal is on approaches for systematic identification, modularization, representation, and composition of crosscutting concerns, i.e., the aspects and evaluation of such approaches and their impact on improving quality attributes of software systems. This volume, the 12th in the Transactions on Aspect-Oriented Software Development series, contains one regular paper, on modular reasoning in aspect-oriented languages from a substitution perspective, and four extended, improved papers selected from those presented at Modularity 2014. Topics covered include novel dynamic semantics through delegation proxies, modularity potential detection based on co-change clusters, improvements in reusability for components of semantic specifications of programming languages, and probabilistic model checking applied to dynamically generated members of a product line.

## Inhaltsverzeichnis

### Modular Reasoning in Aspect-Oriented Languages from a Substitution Perspective

Abstract
In object-oriented languages, a notion of behavioural subtyping is needed to enable modular reasoning. This is no longer sufficient when such languages are extended with aspects. In general, all aspects need to be inspected in order to understand the behaviour of a single method or proceed call, which complicates reasoning about aspect-oriented programs. In this paper, we present an approach to modular reasoning that consists of two parts. First, the advice substitution principle, based on behavioural subtyping, identifies when it is possible to remain unaware of an advice while preserving modular reasoning. Second, in cases where it is undesired or impossible to be unaware of an advice, a simple specification clause can be used to restore modular reasoning and to become aware of this advice. We show that our approach effectively enables modular reasoning about pre- and postconditions in a minimal aspect-oriented language called ContractAJ. To ensure the approach is used correctly, we also provide a runtime contract enforcement algorithm that is specified in ContractAJ, and implemented in AspectJ.
Tim Molderez, Dirk Janssens

### Propagation of Behavioral Variations with Delegation Proxies

Abstract
Scoping behavioral variations to dynamic extents is useful to support non-functional concerns that otherwise result in cross-cutting code. Unfortunately, such forms of scoping are difficult to obtain with traditional reflection or aspects. We propose delegation proxies, a dynamic proxy model that supports behavioral intercession through the interception of various interpretation operations. Delegation proxies permit different behavioral variations to be easily composed together. We show how delegation proxies enable behavioral variations that can propagate to dynamic extents. We demonstrate our approach with examples of behavioral variations scoped to dynamic extents that help simplify code related to safety, reliability, and monitoring.
Camille Teruel, Erwann Wernli, Stéphane Ducasse, Oscar Nierstrasz

### Co-change Clusters: Extraction and Application on Assessing Software Modularity

Abstract
The traditional modular structure defined by the package hierarchy suffers from the dominant decomposition problem and it is widely accepted that alternative forms of modularization are necessary to increase developer’s productivity. In this paper, we propose an alternative form to understand and assess package modularity based on co-change clusters, which are highly inter-related classes considering co-change relations. We evaluate how co-change clusters relate to the package decomposition of four real-world systems. The results show that the projection of co-change clusters to packages follows different patterns in each system. Therefore, we claim that modular views based on co-change clusters can improve developers’ understanding on how well-modularized are their systems, considering that modularity is the ability to confine changes and evolve components in parallel.
Luciana Lourdes Silva, Marco Tulio Valente, Marcelo de A. Maia

### Reusable Components of Semantic Specifications

Abstract
Semantic specifications of programming languages typically have poor modularity. This hinders reuse of parts of the semantics of one language when specifying a different language – even when the two languages have many constructs in common – and evolution of a language may require major reformulation of its semantics. Such drawbacks have discouraged language developers from using formal semantics to document their designs.
In the PLanCompS project, we have developed a component-based approach to semantics. Here, we explain its modularity aspects, and present an illustrative case study: a component-based semantics for Caml Light. We have tested the correctness of the semantics by running programs on an interpreter generated from the semantics, comparing the output with that produced on the standard implementation of the language.
Our approach provides good modularity, facilitates reuse, and should support co-evolution of languages and their formal semantics. It could be particularly useful in connection with domain-specific languages and language-driven software development.
Martin Churchill, Peter D. Mosses, Neil Sculthorpe, Paolo Torrini

### Probabilistic Model Checking for Feature-Oriented Systems

Abstract
Within product lines, collections of several related products are defined through their commonalities in terms of features rather than specifying them individually one-by-one. In this paper we present a compositional framework for modeling dynamic product lines by a state-based formalism with both probabilistic and nondeterministic behaviors. Rules for feature changes in products made during runtime are formalized by a coordination component imposing constraints on possible feature activations and deactivations. Our framework supports large-scaled product lines described through multi-features, i.e., where products may involve multiple instances of a feature.
To establish temporal properties for products in a product line, verification techniques have to face a combinatorial blow-up that arises when reasoning about several feature combinations. This blow-up can be avoided by family-based approaches exploiting common feature behaviors. We adapt such approaches to our framework, allowing for a quantitative analysis in terms of probabilistic model checking to reason, e.g., about energy and memory consumption, monetary costs, or the reliability of products. Our framework can also be used to compute strategies how to trigger feature changes for optimizing quantitative objectives using probabilistic model-checking techniques.
We present a natural and conceptually simple translation of product lines into the input language of the prominent probabilistic model checker $$\textsc {Prism}$$ and show feasibility of this translation within a case study on an energy-aware server platform product line comprising thousands of products. To cope with the arising complexity, we follow the family-based analysis scheme and apply symbolic methods for a compact state-space representation.
Clemens Dubslaff, Christel Baier, Sascha Klüppelholz

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