Ludo: A Case Study for Graph Transformation Tools

In this paper we describe the Ludo case, one of the case studies of the AGTIVE 2007 Tool Contest (see [22]). After summarising the case description, we give an overview of the submitted solutions. In particular, we propose a number of dimensions along which choices had to be made when solving the case, essentially setting up a solution space; we then plot the spectrum of solutions actually encountered into this solution space. In addition, there is a brief description of the special features of each of the submissions, to do justice to those aspects that are not distinguished in the general solution space

Graph-Based Specification and Simulation of Featherweight Java with Around Advice

In this paper we specify an operational run-time semantics of Assignment Featherweight Java -- a minimal subset of Java with assignments -- with around advice, using graph transformations. We introduce a notion of correctness of our specification with respect to an existing semantics and claim a number of advantages over traditional mathematical notations, that come forth from the executable nature of graph-transformation-based semantics. Using test programs as graphs during specification of the semantics, simulation can help in verifying the correctness of the rules simply by testing, increasing the rigorousness of the specification process. Also, execution of the semantics results in a state space that can be used for analysis and verification, giving rise to an effective method for aspect program verification. As a criterion for correctness, we use a structural operational semantics of this language from the so-called Common Aspect Semantics Base

A Graph-Transformation-Based Semantics for Analysing Aspect Interference

AOP is widely accepted as a language concept to improve separation of concerns. However, the separate development of aspects may introduce semantic problems in the composition of the aspects and the base system. We propose a modular and graph-based verification approach. An aspect-oriented program is represented by a graph. A graph production system specifying the semantics of the language allows us to generate a transition system of the execution of the program. This can be used to analyse and verify different properties of the system. We show that, currently, it allows the detection of semantic differences between advice orderings on shared joinpoints, which is one of the semantic problems referred to above

A Graph-Transformation-Based Simulation Approach for Analysing Aspect Interference on Shared Join Points

Aspects that in isolation behave correctly, may interact when being combined. When interaction changes an aspect's behaviour or disables an aspect, we call this interference. One particular type of interference occurs when aspects are applied to shared join points, since then the ordering of the aspects can also influence the behaviour of the composition. We present an approach to detect aspect interference at shared join points. Aspect compositions are modelled by using a graph production system for modelling aspect-language semantics. A graph-based model of a join point is generated from the source-code of the system. This graph is transformed into a runtime-state representation. Combined with the production system (and the correct tooling) the execution of the aspects is simulated. This simulation results in a labelled transition system that can be used to analyse and verify different properties of the system at the join point. Simulation of the entire system can be computationally expensive. In our approach, we decide to abstract base system execution into non-deterministic valuation and carefully choosing advice semantics, such that simulation of the entire system can be avoided

Reasoning about Semantic Conflicts between Aspects

Aspects have been successfully promoted as a means to improve the modularization of software in the presence of crosscutting concerns. The socalled aspect interference problem is considered to be one of the remaining challenges of aspect-oriented software development: when multiple aspects share the same join point, undesired behavior may emerge. Such behavior is not necessarily caused by a wrong implementation of the individual aspects, but may be the result of composition of the independently programmed aspects at the shared join point. This paper presents a language-independent technique to detect semantic conflicts among aspects that are superimposed on the same join point

Effects of Iron Limitation on the Degradation of Toluene by Pseudomonas Strains Carrying the TOL (pWWO) Plasmid

Most aerobic biodegradation pathways for hydrocarbons involve iron-containing oxygenases. In iron-limited environments, such as the rhizosphere, this may influence the rate of degradation of hydrocarbon pollutants. We investigated the effects of iron limitation on the degradation of toluene by Pseudomonas putida mt2 and the transconjugant rhizosphere bacterium P. putida WCS358(pWWO), both of which contain the pWWO (TOL) plasmid that harbors the genes for toluene degradation. The results of continuous-culture experiments showed that the activity of the upper-pathway toluene monooxygenase decreased but that the activity of benzyl alcohol dehydrogenase was not affected under iron-limited conditions. In contrast, the activities of three meta-pathway (lower-pathway) enzymes were all found to be reduced when iron concentrations were decreased. Additional experiments in which citrate was used as a growth substrate and the pathways were induced with the gratuitous inducer o-xylene showed that expression of the TOL genes increased the iron requirement in both strains. Growth yields were reduced and substrate affinities decreased under iron-limited conditions, suggesting that iron availability can be an important parameter in the oxidative breakdown of hydrocarbons