Many large software systems are variability-rich, object-oriented, and implemented in a single code base. They then rely on multiple traditional techniques (inheritance, patterns) to realize variability, making these implementations not explicit. This directly hampers the comprehension of variability implementations, especially for newcomers in a project that need, in a short time, to understand the most important parts. In this paper, we propose VariCity, a visualization using the city metaphor to exhibit zones of interest, being zones of high density of variability implementations. The different forms of variability implementations are first detected through the usage of symmetries in code (e.g., inheritance defines a substitution symmetry between the immutable part of the superclass and the possible changes in its subclasses). VariCity then creates a 3D city representation with buildings being classes while the metrics on the number of symmetries (e.g., the number of overloaded methods, influence the building size, and their color if they are heavily loaded in symmetries). Contrary to the usual package-based organization in code-related city representations, the city streets are arranged according to the usage relationships between classes. Inheritance is simply represented with hoverable aerial links. Variability-related design patterns are depicted as buildings with specific geometric forms, while some classes specified as entry points can help in shaping the whole city organization. We also report on the evaluation of VariCity on a set of large object-oriented systems, showing that several usage scenarios helping a newcomer to spot critical variability-related zones are covered.

Despite exciting prospects, the development of 360° videos is persistently hindered by the difficulty to stream them. To reduce the data rate, existing streaming strategies adapt the video rate to the user's Field of View (FoV), but the difficulty of predicting the FoV and persistent lack of bandwidth are important obstacles to achieve best experience. In this article we exploit the recent findings on human attention in VR to introduce a new additional degree of freedom for the streaming algorithm to leverage: Virtuall Walls (VWs) are designed to translate bandwidth limitation into a new type of impairment allowing to preserve the visual quality by subtly limiting the user's freedom in well-chosen periods. We carry out experiments with 18 users and confirm that, if the VW is positioned after the exploration phase in scenes with concentrated saliency, a substantial fraction of users seldom perceive it. With a double-stimulus approach, we show that, compared with a reference with no VW consuming the same amount of data, VW can improve the quality of experience. Simulation of different FoV-based streaming adaptations with and without VW show that VW enables reduction in stalls and increases quality in FoV.

Cinematic Virtual Reality (VR) has the potential of touching the masses with new exciting experiences, but faces two main hurdles: one is the ability to stream these videos, another is their design and creation. Indeed, rates are much higher and in addition to discomfort and sickness that might arise in fully immersive experience with a headset, users might get lost when exploring a 360° videos and miss main elements required to understand the underlying plot. We take an innovative approach by addressing jointly the creation and streaming problems. We introduce a technique called snap-changes, aimed at directing viewers to points of interest pre-defined by the content producer. We design a VR editing tool and a custom 360° video player, to provide the content creator with the ability to drive the user's attention, and report results from two sets of user experiments that indicate that snap-changes indeed help reduce user's head motion.

International audience

Visualization systems such as dashboards are commonly used to analyze data and support users in their decision making, in communities as different as medical care, transport and software engineering. The increasing amount of data produced and continuous development of new visualizations exacerbate the difficulty of designing such dashboards, while the visualization need is broaden to specialist and non-specialist final users. In this context, we offer a multi-user approach, based on Model Driven Engineering (MDE). The idea is for the designer to express the visualization need by characterization, according to a given taxonomy. We provide a Domain Specific Language (DSL) to design the system and a Software Product Line (SPL) to capture the technological variability of visualization widgets. We performed a user study, using a software project management use case, to validate if dashboard users and designers are able to use a taxonomy to express their visualization need.

We propose a reflective model to express and to automatically manage dependencies between objects. This model describes reflective facilities which enable the changing of language semantics. Although the importance of inter-object dependencies is well accepted, there is only limited object-oriented language support for their specification and implementation. In response to this lack of expressiveness of object models, the FLO language integrates dependency management into the object oriented paradigm. Dependencies are described as first class objects and FLO automatically maintains the consistency of the dependency graph.In this paper, we first show how a user can declare dependencies and how the system maintains the consistency of the graph of expressed dependencies. In a second part, we focus on the implementation of this management by controlling the messages sent to linked objects. In order to make dependency management orthogonal to other application concerns, we propose an abstraction of message handling, implemented with meta-objects. We illustrate the extensibility of our language with different control behavior implementations, in particular we study different implementations of the global control of message propagation flow.

The authors point out the reasons that lead us to distribute modular applications and how they distribute them. They illustrate their ideas with an example of an expert system shell.