Francesca Bugiotti

Uniform access to NoSQL systems

Non-relational databases (often termed as NoSQL) have recently emerged and have generated both interest and criticism. Interest because they address requirements that are very important in large-scale applications, criticism because of the comparison with well known relational achievements. One of the major problems often mentioned is the heterogeneity of the languages and of the interfaces they offer to developers and users. Different platforms and languages have been proposed, and applications developed for one system require significant effort to be migrated to another one. Here we propose a common programming interface to NoSQL systems called SOS (Save Our Systems). Its goal is to support application development by hiding the specific details of the various systems. It is based on a metamodelling approach, in the sense that the specific interfaces of the individual systems are mapped to a common one. The tool provides interoperability as well, since a single application can interact with several systems at the same time. HighlightsA platform that can provide uniform access to multiple NoSQL systems is provided.Key-value stores, extensible record stores and document stores are handled.It supports application development at high level as well as interoperability between diverse systems.

Uniform access to non-relational database systems: the SOS platform

Non-relational databases (often termed as NoSQL) have recently emerged and have generated both interest and criticism. Interest because they address requirements that are very important in large-scale applications, criticism because of the comparison with well known relational achievements. One of the major problems often mentioned is the heterogeneity of the languages and the interfaces they offer to developers and users. Different platforms and languages have been proposed, and applications developed for one system require significant effort to be migrated to another one. Here we propose a common programming interface to NoSQL systems (and also to relational ones) called SOS (Save Our Systems). Its goal is to support application development by hiding the specific details of the various systems. It is based on a metamodeling approach, in the sense that the specific interfaces of the individual systems are mapped to a common one. The tool provides interoperability as well, since a single application can interact with several systems at the same time.

Database Design for NoSQL Systems

We propose a database design methodology for NoSQL systems. The approach is based on NoAM (NoSQL Abstract Model), a novel abstract data model for NoSQL databases, which exploits the commonalities of various NoSQL systems and is used to specify a system-independent representation of the application data. This intermediate representation can be then implemented in target NoSQL databases, taking into account their specific features. Overall, the methodology aims at supporting scalability, performance, and consistency, as needed by next-generation web applications.

MISM: A Platform for Model-Independent Solutions to Model Management Problems

Model management is a metadata-based approach to database problems aimed at supporting the productivity of developers by providing schema manipulation operators. Here we propose MISM (Model Independent Schema Management), a platform for model management offering a set of operators to manipulate schemas, in a manner that is both model-independent (in the sense that operators are generic and apply to schemas of different data models) and model-aware (in the sense that it is possible to say whether a schema is allowed for a data model). This is the first proposal for model management in this direction. We consider the main operators in model management: merge, diff, and modelgen. These operators play a major role in solving various problems related to schema evolution (such as data integration, data exchange or forward engineering), and we show in detail a solution to a major representative of the class, the round-trip engineering problem.

A runtime approach to model-independent schema and data translation

A runtime approach to model-generic translation of schema and data is proposed. It is based on our previous work on MIDST, a platform conceived to perform translations in an off-line fashion. In the original approach, the source database is imported into a dictionary, where it is stored according to a universal model. Then, the translation is applied within the tool as a composition of elementary transformation steps, specified as Datalog programs. Finally, the result is exported into the operational system. Here we illustrate a new, lightweight approach where the database is not imported. The tool needs only to know the model and the schema of the source database and generates views on the operational system that transform the underlying data (stored in the source schema) according to the corresponding schema in the target model. Views are generated in an almost automatic way, on the basis of the Datalog rules for schema translation.

A runtime approach to model-generic translation of schema and data

To support heterogeneity is a major requirement in current approaches to integration and transformation of data. This paper proposes a new approach to the translation of schema and data from one data model to another, and we illustrate its implementation in the tool MIDST-RT. We leverage on our previous work on MIDST, a platform conceived to perform translations in an off-line fashion. In such an approach, the source database (both schema and data) is imported into a repository, where it is stored in a universal model. Then, the translation is applied within the tool as a composition of elementary transformation steps, specified as Datalog programs. Finally, the result (again both schema and data) is exported into the operational system. Here we illustrate a new, lightweight approach where the database is not imported. MIDST-RT needs only to know the schema of the source database and the model of the target one, and generates views on the operational system that expose the underlying data according to the corresponding schema in the target model. Views are generated in an almost automatic way, on the basis of the Datalog rules for schema translation. The proposed solution can be applied to different scenarios, which include data and application migration, data interchange, and object-to-relational mapping between applications and databases.

SOS (save our systems): a uniform programming interface for non-relational systems

The recent growth of non-relational databases (often termed as NoSQL) is an interesting phenomenon that has generated both interest and criticism. One of the major drawbacks that is often referred to is the heterogeneity of the languages and interfaces they offer to developers and users. SOS is proposed as a common interface to them, in order to support application development by hiding the specific details of the various systems. It is based on a metamodeling approach, in the sense that the specific interfaces of the various systems are mapped to a common one. The tool provides interoperability as well, since a single application can interact with several systems at the same time. The demonstration will focus on a simple yet powerful application scenario which accesses three different NoSQL systems.

From Schema and Model Translation to a Model Management System

Model management addresses problems dealing with forms of collaboration among heterogeneous databases. This collaboration may include exchange of data, schema integration, synchronization, translation and, in general, any issue characterized by a data evolving scenario. It provides a structured framework allowing standard solutions to data programmability problems in terms of the application of some recurring operators. The main mid-term target in this field is the definition of a model management system, a software platform providing the data architect with a complete set of tools addressing a wide spectrum of possible problems. In this paper we recall MIDST, a platform that works as an applicator of schema transformations. It was firstly conceived to perform model-independent schema and data translation. Then it has been extended to an applicator of general schema transformations including model management operators. Leveraging on MIDST rich representation of models, schemas and data based on a metalevel approach, we reason about potentialities and possible developments of this platform with the target of laying the basis for a real runtime model management system.

EXLEngine: executable schema mappings for statistical data processing

Data processing is the core of any statistical information system. Statisticians are interested in specifying transformations and manipulations of data at a high level, in terms of entities of statistical models such as time series. We illustrate here an experience at the Bank of Italy where (i) a language, EXL, has been defined for the declarative specification of statistical programs, (ii) an approach for the translation of EXL code into executables in various target systems has been developed, and (iii) a concrete implementation, EXLEngine, has been carried out. The approach leverages on schema mappings as an intermediate specification step, in order to facilitate the translation from EXL towards several target systems.

Modeling Strategies for Storing Data in Distributed Heterogeneous NoSQL Databases.

In this work, we propose HerM (Heterogeneous Distributed Model), a NoSQL data modeling approach which supports the use of multiple heterogeneous NoSQL systems in a distributed environment. We define the conceptual elements necessary for data modeling, and we identify optimized data distribution patterns. We implemented a flexible framework, where we deployed our proposed modeling strategies and that we evaluated comparing our approach against native the NoSQL data distribution methodology provided by the NoSQL databases MongoDB.