The management of Big Data requires flexible systems to handle the heterogeneity of data models as well as the complexity of analytical workflows. Traditional systems like data warehouses have reached their limits due to their rigid schema-on-write paradigm, that requires well identified and defined use cases to ingest data. Data lakes, with their schema-on-read paradigm, have been proposed as more flexible systems in which raw data are directly stored in their original format associated with metadata, to be accessed and transformed only when users need to process or analyze them. Thus, it is necessary to define and control the different levels of abstraction and the dependencies among functionalities of a data lake to use it efficiently. In this article, we present a formal framework aiming to define a data lake pattern and to unify the interactions among the functionalities. We use the category theory as theoretical foundations to benefit from its high level of abstraction and its compositionality. By relying on different categories and functors, we ensure the navigation among the functionalities and allow the composition of multiples operations, while keeping track of the entire lineage of data. We also show how our framework can be applied on a simple example of data lake.

Polystores are of primary importance to tackle the diversity and the volume of Big Data, as they propose to store data according to specific use cases. Nevertheless, analytics frameworks often lack a uniform interface allowing to fully access and take advantage of the various models offered by the polystore. It also should be ensured that the typing of the algebraic expressions built with data manipulation operators can be checked and that schema can be inferred before starting to execute the operators (type-safe).

The paper presents a methodology based on data model translation for the management of interoperable information systems. The key feature of this solution are: 1) a set of abstract metatypes that capture the characteristics of various modeling concepts; and 2) the organization of the metatypes in a generalization hierarchy to allow unification and correlation of data models. Description logic formalism is used to provide formal specification of the metatypes and a tool called "Strategic Hierarchy Builder" is defined to build the metatype hierarchy semi-automatically. The Strategic Hierarchy Builder organizes the hierarchy and implements an extensible metamodel in which new metatypes are created by specialization of existing metatypes.