Section: Overall Objectives

Introduction

Modern science such as agronomy, bio-informatics, astronomy and environmental science must deal with overwhelming amounts of experimental data produced through empirical observation and simulation (http://www.computational-sustainability.org ). Such data must be processed (cleaned, transformed, analyzed) in all kinds of ways in order to draw new conclusions, prove scientific theories and produce knowledge. However, constant progress in scientific observational instruments (e.g. satellites, sensors, large hadron collider) and simulation tools (that foster in silico experimentation, as opposed to traditional in situ or in vivo experimentation) creates a huge data overload. For example, climate modeling data are growing so fast that they will lead to collections of hundreds of exabytes (${10}^{18}$ bytes) expected by 2020.

Scientific data is also very complex, in particular because of heterogeneous methods used for producing data, the uncertainty of captured data, the inherently multi-scale nature (spatial scale, temporal scale) of many sciences and the growing use of imaging (e.g. satellite images), resulting in data with hundreds of attributes, dimensions or descriptors. Processing and analyzing such massive sets of complex scientific data is therefore a major challenge since solutions must combine new data management techniques with large-scale parallelism in cluster, grid or cloud environments.

Furthermore, modern science research is a highly collaborative process, involving scientists from different disciplines (e.g. biologists, soil scientists, and geologists working on an environmental project), in some cases from different organizations distributed over different countries. Each discipline or organization tends to produce and manage its own data, in specific formats, with its own processes. Thus, integrating distributed data and processes gets difficult as the amounts of heterogeneous data grow.

Despite their variety, we can identify common features of scientific data: big data; manipulated through complex, distributed workflows; typically complex, e.g. multidimensional or graph-based; with uncertainty in the data values, e.g., to reflect data capture or observation; important metadata about experiments and their provenance; and mostly append-only (with rare updates).

Generic data management solutions (e.g. relational DBMS) which have proved effective in many application domains (e.g. business transactions) are not efficient for dealing with scientific data, thereby forcing scientists to build ad-hoc solutions which are labor-intensive and cannot scale. In particular, relational DBMSs have been lately criticized for their “one size fits all” approach. Although they have been able to integrate support for all kinds of data (e.g., multimedia objects, XML documents and new functions), this has resulted in a loss of performance and flexibility for applications with specific requirements because they provide both “too much” and “too little”. Therefore, it has been argued that more specialized DBMS engines are needed. For instance, column-oriented DBMSs, which store column data together rather than rows in traditional row-oriented relational DBMSs, have been shown to perform more than an order of magnitude better on decision-support workloads. The “one size does not fit all” counter-argument generally applies to cloud data management as well. Cloud data can be very large, unstructured (e.g. text-based) or semi-structured, and typically append-only (with rare updates). And cloud users and application developers may be in high numbers, but not DBMS experts. Therefore, current cloud data management solutions have traded consistency for scalability, simplicity and flexibility. As alternative to relational DBMS (which use the standard SQL language), these solutions have been quoted as Not Only SQL (NOSQL) by the database research community.

The three main challenges of scientific data management can be summarized by: (1) scale (big data, big applications); (2) complexity (uncertain, multi-scale data with lots of dimensions), (3) heterogeneity (in particular, data semantics heterogeneity). The overall goal of Zenith is to address these challenges, by proposing innovative solutions with significant advantages in terms of scalability, functionality, ease of use, and performance. To produce generic results, these solutions will be in terms of architectures, models and algorithms that can be implemented in terms of components or services in specific computing environments, e.g. grid, cloud. To maximize impact, a good balance between conceptual aspects (e.g. algorithms) and practical aspects (e.g. software development) is necessary. We plan to design and validate our solutions by working closely with scientific application partners (CIRAD, INRA, CEMAGREF, etc.). To further validate our solutions and extend the scope of our results, we also want to foster industrial collaborations, even in non scientific applications, provided that they exhibit similar challenges.