Amela Fejza

Query optimizers built on the transformation-based Volcano/Cascades framework are used in many database systems. Transformations proposed earlier on the logical query dag (LQDAG) data structure, which is key in such a framework, focus only on recursion-free queries. In this paper, we propose the recursive logical query dag (RLQDAG) which extends the LQDAG with the ability to capture and transform recursive queries, leveraging recent developments in recursive relational algebra. Specifically, this extension includes: (i) the ability of capturing and transforming sets of recursive relational terms thanks to (ii) annotated equivalence nodes used for guiding transformations that are more complex in the presence of recursion; and (iii) RLQDAG rewrite rules that transform sets of subterms in a grouped manner, instead of transforming individual terms in a sequential manner; and that (iv) incrementally update the necessary annotations. Core concepts of the RLQDAG are formalized using a syntax and formal semantics with a particular focus on subterm sharing and recursion. The result is a clean generalization of the LQDAG transformation-based approach, enabling more efficient explorations of plan spaces for recursive queries. An implementation of the proposed approach shows significant performance gains compared to the state-of-the-art.

Plan enumeration is one of the most crucial components in relational query optimization. We demonstrate RLQDAG, a system implementation of a top-down plan enumerator for the purpose of transforming sets of recursive relational terms efficiently. We describe a complete system of query optimization with parsers and compilers adapted for recursive queries over knowledge and property graphs. We focus on the enumeration component of this sytem, the RLQDAG, and especially on its efficiency in generating plans out of reach of other approaches. We show graphical representations of explored plan spaces for queries on real datasets. We demonstrate the plan enumerator and its benefits in finding more efficient query plans.

We demonstrate a system for recursive query answering over graphs. The system is based on a complete implementation of the recursive relational algebra 𝜇-RA, extended with parsers and compilers adapted for queries over knowledge and property graphs. Each component of the system comes with novelty for processing recursion. As a result, one can formulate, optimize and efficiently answer expressive queries that navigate recursively along paths in different types of graphs. We demonstrate the system on real datasets and show how it performs considering other state-of-the-art systems.

Early identification of patients at risk of developing complications during their hospital stay is currently a challenging issue in healthcare. Complicationsinclude hospitalacquired infections, admissions to intensive care units, and in-hospital mortality. Being able to accurately predict the patients’ outcomes is a crucial prerequisite for tailoring the care that certain patients receive, if it is believed that they will do poorly without additional intervention. We consider the problem of complication risk prediction, such as inpatient mortality, from the electronic health records of the patients. We study the question of making predictions on the first day at the hospital, and of making updated mortality predictions day after day during the patient’s stay. We develop distributed models that are scalable and interpretable. Key insights include analysing diagnoses known at admission and drugs served, which evolve during the hospital stay. We leverage a distributed architecture to learn interpretable models from training datasets of gigantic size. We test our analyses with more than one million of patients from hundreds of hospitals, and report on the lessons learned from these experiments.

Early identification of patients at risk of developing complications during their hospital stay is currently one of the most challenging issues in healthcare. Complications include hospital-acquired infections, admissions to intensive care units, and in-hospital mortality. Being able to accurately predict the patients’ outcomes is a crucial prerequisite for tailoring the care that certain patients receive, if it is believed that they will do poorly without additional intervention. We consider the problem of complication risk prediction, such as inpatient mortality, from the electronic health records of the patients. We study the question of making predictions on the first day at the hospital, and of making updated mortality predictions day after day during the patient’s stay. We develop distributed models that are scalable and interpretable. Key insights include analysing diagnoses known at admission and drugs served, which evolve during the hospital stay. We leverage a distributed architecture to learn interpretable models from training datasets of gigantic size. We test our analyses with more than one million of patients from hundreds of hospitals, and report on the lessons learned from these experiments.

In order to develop and enhance an augmentative and alternative communication (AAC), gaze is often considered as one of the most natural way and one of the easiest to set up in order to support individuals with multiple disabilities to interact with their environment. For children who start naturally from scratch, who have in addition such difficulties, it is a strong challenge even to acquire or to support the required basic knowledge. Games are often considered a good way to learn. Games designed for eye-trackers, i.e. electronic devices able to compute the position of the gaze, allow children to discover the power of their eyes and the consequences of the actions triggered by their gazes. Video games can be a good way to improve basic requirements as gaze fixation and gaze pursuit as well as conventions like rewards or dwell interactions often used in AAC tools. In this article, we present the GazePlay project which main contribution is a free and open-source software which gathers several mini-games playable with all eye-trackers including low cost ones.