Using Model Types to Support Contract-Aware Model Substitutability

International audienceModel typing brings the benefit associated with well-defined type systems to model-driven development (MDD) through the assignment of specific types to models. In particular, model type systems enable reuse of model manipulation operations (e.g., model transformations), where manipulations defined for models of a supertype can be used to manipulate models of subtypes. Existing model typing approaches are limited to structural typing defined in terms of object-oriented metamodels (e.g., MOF) in which the only structural (well-formedness) constraints are those that can be expressed directly in metamodeling notations (e.g., multiplicity and element containment constraints). In this paper we describe an extension to model typing that takes into consideration structural invariants, other than those that can be expressed directly in metamodeling notation, and specifications of behaviors associated with model types. The approach supports contract-aware substitutability, where contracts are defined in terms of invariants and pre-/postconditions expressed using OCL. Support for behavioral typing paves the way for behavioral substitutability. We also describe a technique to rigorously reason about model type substitutability as supported by contracts and apply the technique in use cases from the optimizing compiler community

Tau Be or not Tau Be? - A Perspective on Service Compatibility and Substitutability

One of the main open research issues in Service Oriented Computing is to propose automated techniques to analyse service interfaces. A first problem, called compatibility, aims at determining whether a set of services (two in this paper) can be composed together and interact with each other as expected. Another related problem is to check the substitutability of one service with another. These problems are especially difficult when behavioural descriptions (i.e., message calls and their ordering) are taken into account in service interfaces. Interfaces should capture as faithfully as possible the service behaviour to make their automated analysis possible while not exhibiting implementation details. In this position paper, we choose Labelled Transition Systems to specify the behavioural part of service interfaces. In particular, we show that internal behaviours (tau transitions) are necessary in these transition systems in order to detect subtle errors that may occur when composing a set of services together. We also show that tau transitions should be handled differently in the compatibility and substitutability problem: the former problem requires to check if the compatibility is preserved every time a tau transition is traversed in one interface, whereas the latter requires a precise analysis of tau branchings in order to make the substitution preserve the properties (e.g., a compatibility notion) which were ensured before replacement.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Orchestrated Session Compliance

We investigate the notion of orchestrated compliance for client/server interactions in the context of session contracts. Devising the notion of orchestrator in such a context makes it possible to have orchestrators with unbounded buffering capabilities and at the same time to guarantee any message from the client to be eventually delivered by the orchestrator to the server, while preventing the server from sending messages which are kept indefinitely inside the orchestrator. The compliance relation is shown to be decidable by means of 1) a procedure synthesising the orchestrators, if any, making a client compliant with a server, and 2) a procedure for deciding whether an orchestrator behaves in a proper way as mentioned before.Comment: In Proceedings ICE 2015, arXiv:1508.0459

When Systems Engineering Meets Software Language Engineering

International audienceThe engineering of systems involves many different stakeholders, each with their own domain of expertise. Hence more and more organizations are adopting Domain Specific Languages (DSLs) to allow domain experts to express solutions directly in terms of relevant domain concepts. This new trend raises new challenges about designing DSLs, evolving a set of DSLs and coordinating the use of multiple DSLs for both DSL designers and DSL users. This paper explores various dimensions of these challenges, and outlines a possible research roadmap for addressing them. The message of this paper is also to claim that if language engineering techniques to design any single (disposable) language are mature, the language engineering community needs to fundamentally change its view on software language design. We need to take the next step and adopt the perspective that a software language is, fundamentally, software too and thus the result of a composition of design decisions. These design decisions should be represented as first-class entities in the software languages workbench and it should be possible, during the language lifecycle, to add, remove and change language design decisions with limited effort to go from continuous design to continuous meta-design

Implementing the 35 Hour Workweek by Means of Overtime Taxation

In this paper we study the implications of taxing overtime work in order to reduce the workweek. To this purpose we study the roles played by team work, commuting costs and idiosyncratic output risk in determining the choice of the workweek. In order to obtain reliable estimates of the consequences of our policy experiment, we calibrate our model economy to the substitutability between overtime and employment using business cycle information. We find that a tax-rate of 12% of overtime wages implements the desired reduction of the workweek from 40 to 35 hours (12.5%). We also find that this tax change increases employment by 7% and reduces output and productivity by 10.2% and 4.2%, respectively. We also study a model economy with cross-sectional variations in the workweek that arise from plant-specific output risk and we find that in this model economy the tax-rates needed to achieve the same workweek reduction are significantly larger. Finally, we find that taxing overtime dampens business cycle fluctuations and that its welfare costs seem to be very largeWorkweek, Overtime, 35 Hours week, Labour Policy

'Don’t leave me this way!' Drivers of parental hostility and employee spin-offs’ performance

Many entrepreneurs commercialize an idea they initially developed as employees of an incumbent firm. While some face retaliatory reactions from their (former) employer, others are left alone or even supported. It is not clear, however, why some employee spin-offs face parental hostility while others do not, and to what extent this parental hostility affects employee spin-offs’ performance. Integrating the resource-based view with insights on competition and retaliation, we propose that parental hostility increases with the (perceived) competitive threat posed by an employee spin-off. Specifically, we advance employee spin-offs’ initial strategic actions (offering substitute products, hiring employees of the parent, and attempting to first develop the idea inside the parent) as key drivers of parental hostility and consequent spin-off performance. Results from a pooled dataset of 1083 employee spin-offs in Germany confirm that these initial strategic actions trigger parental hostility, which in turn, and contrary to expectations, positively affects employee spin-offs’ innovation and economic performance. These results advance the literature on employee spin-offs in several ways and have important practical implications

Fair Trade

This paper deals with the behavior of fair trade organizations in an oligopolistic setting in which the vertically integrated fair trade firm produces a commodity which is a weak substitute for another commodity. Profit-maximizing oligopolists are vertically disintegrated and produce for both markets and the fair trade firm can charge a premium to consumers due to a "warm glow effect" that depends on the wage paid to fair trade producers. We show that trade integration will unambiguously increase the size of the fair trade firm. However, the relative size compared to oligopolists shrinks with integration. The effect of a change in substitutability between the two commodities on markets shares depends on the relative market potential. Furthermore, we show that the warm glow effect does not support an expansion of the volume of fair trade.