Abstract
Use case driven development methodologies put use cases at the center of the software development process. However, in order to support automated development and analysis, use cases need to be appropriately formalized. This will also help guarantee consistency between requirements specifications and developed solutions. Formal methods tend to suffer from take up issues, as they are usually hard to accept by industry. In this context, it is relevant not only to produce languages and approaches to support formalization, but also to perform their validation. In previous works we have developed an approach to formalize use cases resorting to ontologies. In this paper we present the validation of one such approach. Through a three stage study, we evaluate the acceptance of the language and supporting tool. The first stage focusses on the acceptance of the process and language, the second on the support the tool provides to the process, and finally the third one on the tool's usability aspects. Results show test subjects found the approach feasible and useful and the tool easy to use.

Abstract
In this paper, we develop a theoretical model that enriches the literature on the pros and cons of ownership unbundling vis-A -vis lighter unbundling frameworks in the natural gas markets. For each regulatory framework, we compute equilibrium outcomes when an incumbent firm and a new entrant compete A la Cournot in the final gas market. We find that the entrant's contracting conditions in the upstream market and the transmission tariff are key determinants of the market structure in the downstream gas market (both with ownership and with legal unbundling). We also study how the regulator must optimally set transmission tariffs in each of the two unbundling regimes. We conclude that welfare maximizing tariffs often require free access to the transmission network (in both regulatoy regimes). However, when the regulator aims at promoting the break-even of the regulated transmission system operator, the first-best tariff is unfeasible in both regimes. Hence, we study a more realistic set-up, in which the regulator's action is constrained by the break-even of the regulated firm (the transmission system operator). In this set-up, we find that, for a given transmission tariff, final prices in the downstream market are always higher with ownership unbundling than with legal unbundling.

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This paper proposes an interactive annotation technique for 360 degrees videos that allows the use of traditional video editing techniques to add content to immersive videos. Using the case study of immersive journalism the main objective is to diminish the entry barrier for annotating 360 degrees video pieces, by providing a different annotation paradigm and a set of tools for annotation. The spread of virtual reality systems and immersive content has been growing substantially due to technological progress and cost reductions in equipment and software. From all the technologies employed in virtual reality systems, 360 degrees video is one that currently presents unique conditions to be widely used by various industries -especially for communication purposes. From the various areas that can benefit from the usage of virtual reality systems, the communication field is one that requires innovation in the way that narratives are built, especially in virtual reality systems. In the case of immersive journalism, 360 degrees video technology is currently one of the most used mediums by several media outlets. This kind of news content, whose innovative role should be highlighted, is still being studied in the field of journalism, needing a clearly defined set of rules and good practises. In order to improve the introduction of virtual elements in the 360 degrees videos this paper proposes a set of annotation paradigms for 1) Media information display and 2) Narrative and attention focusing. In this paper we present a list of possible techniques that solve the problem of immersive annotation, as well as a description of a prototype that was developed to test these concepts. The prototype implements an annotation technique based on masked videos and the extension of standard subtitle file formats. Finally a fast-track user study was developed to evaluate the acceptance of the visualisation techniques and to refine the set of tools.

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