Section: New Results

Data Integration

In the context of the CoherentPaaS European project, we have developped the Cloud Multi-datastore Query Language (CloudMdsQL), and its query engine. CloudMdsQL is a functional SQL-like language, capable of querying multiple heterogeneous data stores, e.g. relational, NoSQL or HDFS) [21]. The major innovation is that a CloudMdsQL query can exploit the full power of the local data stores, by simply allowing some local data store native queries to be called as functions, and at the same time be optimized. In [42], we demonstrate CloudMdsQL on two use cases each involving four diverse data stores (graph, document, relational, and key-value) with its corresponding CloudMdsQL queries. The query execution flows are visualized by an embedded real-time monitoring subsystem. In [17], we extend CloudMdsQL to allowing the ad-hoc usage of user defined map/filter/reduce operators in combination with traditional SQL statements, to integrate relational data and big data stored in HDFS and accessed by a data processing framework like Spark. Our experimental validation with several different data stores and representative queries [43] demonstrates the usability of the query language and the benefits from query optimization.

Agronomic Linked Data (AgroLD) [30], [55], [54] is a knowledge system that exploits Semantic Web technology to integrate information on plant species widely studied by the agronomic research community. The objective is to provide the community with a platform for domain specific knowledge, capable of answering complex biological questions and thus facilitating the formulation of new hypotheses. The conceptual framework is based on well-established ontologies in plant sciences such as Gene Ontology, Sequence Ontology, Plant Ontology and Plant Environment Ontology. AgroLD version 1 consists of  50 million knowledge statements (i.e. RDF triples), which will grow in the subsequent versions to provide the required critical mass for hypotheses generation.

AgroLD relyes on AgroPortal [40], a reference ontology repository for the agronomi domain that features ontology hosting and search visualization with services for semantically annotating data with the ontologies. We used the AgroPortal Annotator web service to annotate more than 50 datasets and produced 22% additional triples validated manually. We also developed a dedicated AgroLD vocabulary that bridges the gap between these references ontologies and formalizes their mappings.