Abstract

Abstract
Context: Over the past 20 years, software startups have created many products that have changed human life. Since these companies are creating brand-new products or services, requirements are difficult to gather and highly volatile. Although scientific interest in software development in this context has increased, the studies on requirements engineering in software startups are still scarce and mostly focused on elicitation activities. Objective: This study overcomes this gap by answering how requirements engineering practices are performed in this context. Method: We conducted a grounded theory study based on 17 interviews with software startups practitioners. Results: We constructed a model to show that software startups do not follow a single set of practices but, instead, build a custom process, changed throughout the development of the company, combining different practices according to a set of influences (Founders, Software Development Manager, Developers, Market, Business Model and Startup Ecosystem). Conclusion: Our findings show that requirements engineering activities in software startups are similar to those in agile teams, but some steps vary as a consequence of the lack of an accessible customer.

Abstract

Abstract
The purpose of this study was to measure the subject's sense of presence while they performed a task (riding a bicycle downhill) in a virtual reality (VR) environment and to compare it by body position (standing vs. sitting) and gender. The sample consisted of 35 subjects (19 male and 16 female) between 17 and 33 years of age. A translated and validated Portuguese version of the lgroup Presence Questionnaire (IPQp) and the Reflexive Motor Acts (RMAs), based on direct observation, were used as metrics. The results showed significant differences between body position at the level of Experienced Realism, Spatial Presence and Overall Sense of Presence. When measuring RMAs, it was demonstrated that people in the sitting position presented a higher frequency. We concluded that body position influences perceptions of credibility, which has an impact on the sense of presence. No differences were identified between the genders.

Abstract
Procedural modeling techniques reduce the effort of creating large virtual cities. However, current methodologies do not allow direct user control over the generated models. Associated with this problem, we face the additional problem related to intrinsic ambiguity existing in user selections. In this paper, we propose to address this problem by using a genetic algorithm to generalize user-provided point-and-click selections of building elements. From a few user-selected elements, the system infers new sets of elements that potentially correspond to the user's intention, including the ones manually selected. These sets are obtained by queries over the shape trees generated by the procedural rules, thus exploiting shape semantics, hierarchy and geometric properties. Our system also provides a complete selection-action paradigm that allows users to edit procedurally generated buildings without necessarily explicitly writing queries. The pairs of user selections and procedural operations (the actions) are stored in a tree-like structure, which is easily evaluated. Results show that the selection inference is capable of generating sets of shapes that closely match the user intention and queries are able to perform complex selections that would be difficult to achieve in other systems. User studies confirm this result.

Abstract
Due to technological advances, augmented reality has seen fast growth in the last decades and numerous implementations of this technology have been in favour for a consequent growth of popularity. For this article, an augmented reality system is implemented for smartphone and tested in a cultural heritage environment to evaluate the system performance in the context. In the first stage, several prototypes were developed, and performance tests were executed in a controlled environment to select a solution to implement and evaluate in-situ. The solution found is a marker-based system, held with Vuforia SDK. When the marker is lost for being outside of the field of view, the system will be based on natural features to accomplish user tracking. Visitors from a cultural heritage space – the Roman Ruins of Conimbriga – tested the app and evaluated it. They considered that the presented system should be implemented in the referred cultural space, as well as in other archaeological spaces.