MOD

Data stream management systems (DSMS) process data streams, potentially infinite amounts of data sent by active data sources. Distributed DSMS use networks of interconnected machines to enhance the processing power. Typically, clusters of equal, non-...

In numerous real world applications, one needs to store almost the whole data set in order to compute certain functions of the data, where we require the answer to be exact. In my thesis, I devised a new model for data streaming algorithms where we ...

The demand for mining large datasets using shared-nothing clusters is steadily on the rise. Despite the availability of parallel processing paradigms such as MapReduce, scalable data mining is still a tough problem. Naïve ports of existing algorithms to ...

Although several application domains use unstructured meshes as first-class citizen, there is no dedicated database system which offers querying and manipulation of such objects via a declarative query language. A declarative query language allows users ...

Functional languages provide new approaches to concurrency control, based on techniques such as lazy evaluation and memoization. We have designed and implemented a persistent functional language based on these ideas, which we plan to use for the ...

Data exchange has been one of the most popular topics in the database community for the past several years. Data exchange is essential for transferring, unifying and querying heterogeneous data -- tasks which very often arise in practice. Although the ...

We consider the problem of helping users explore and understand large, high dimensional structured datasets. Such users may issue queries to find data entries of interest. Given the high dimensionality and lack of detailed knowledge of the data, these ...

In this work we present a novel graph-based approach for studying the tractability of query answering over ontologies expressed by means of tuple-generating dependencies (TGDs). We do this by defining a new class of TGDs that subsumes all the other ...

Selecting appropriate indices and materialized views is critical for high performance in relational databases. By example, we show that the problem of schema optimization is also highly relevant for NoSQL databases. We explore the problem of schema ...

Recently, MapReduce frameworks, e.g., Hadoop, have been used extensively in different applications that include tera-byte sorting, machine learning, and graph processing. With the huge volumes of spatial data coming from different sources, there is an ...