MFE 2018-2019 : Web and Information Systems


The primary area of research in the Web and Information Systems laboratory of the the Department of Computer & Decision Engineering concerns information systems (both traditional and on the web). Broadly speaking, we can identify the following major themes in the laboratory's research. The MFE subjects presented below cover these themes.

  • Business Intelligence and Data Warehouses A data warehouse, an evolution of traditional databases, has become the basis of the new generation enterprise information systems. It contains an aggregated and historical view of the operational information of the entreprise. The laboratory's research focuses on the design of data warehouses using the techniques of conceptual modeling and their implementation into current operational platforms.
  • The Semantic Web and Web Data Management The Semantic Web, also known as the Web of Linked Data, aims at enabling people to share structured information on the Web. In the same way as one uses HTML and hyperlinks to publish and connect information on the Web of Documents, one uses the RDF data model and RDF links to publish and connect structured information on the Web of Linked Data. This has the potential to turn the Web into one huge database with structured querying capabilities that vastly exceed the limited keyword search queries so common on the Web of Documents today. Unfortunately, this potential still remains to be realized. In this respect, our work revolves around several issues: (1) the management of ontologies, and especially in the contextualisation, modularization, and the formalization of spatial and temporal aspects in the ontologies; (2) the design of suitable query languages for the web; and (3) the design of efficient evaluation strategies for these query languages.
  • Spatio-temporal databases Today, the management of data located in space is a necessity both for organizations and individuals. The application domains are numerous: cartography, land management, network utility management (electricity, water, transportation, etc.), environment, geomarketing, location-based services. In addition, the spatial dimension is often related to a temporal or historical dimension, which means that the systems must keep track of the evolution in time of the data contained in the database. Our research consists in defining conceptual models that allows the spatial and temporal aspects of applications to be expressed, and the mechanisms allowing the translation of these specifications into operational systems.

Please note that this list of subjects is not exhaustive. Interested students are invited to propose original subjects.

Master Thesis in Collaboration with Euranova

Our laboratory performs collaborative research with Euranova R&D ( The list of subjects proposed for this year by Euranova can be found here.

These subject include topics on distributed graph processing, processing big data using Map/Reduce, cloud computing, and social networks.

Interactive maps of the ULB campuses

This project aims at developing a platform hosting interactive maps of the main campuses of the ULB. These maps will be a convenient guide for students, staff and visitors helping them to reach our campuses, to find buildings or lectures halls and to locate the main facilities (e.g. bike racks, car parks, restaurants, sanitary facilities, etc.). These maps will also be very useful for disabled people allowing them to prepare their visit in advance by identifying accessible routes and facilities. The maps will be then integrated into the new website of the ULB. This project is a unique opportunity to contribute directly to improving the quality of the experience on campus and to work towards a “smart campus”. This project will be developed in collaboration with the Environment and Mobility Service of the ULB. A detailed description of the project can be found here.

Interested? Contact : Esteban Zimányi

Status: available

Dynamic Query Processing on GPU Accelerators

This master thesis is put forward in the context of the DFAQ Research Project: “Dyanmic Processing of Frequently Asked Queries”, funded by the Wiener-Anspach foundation.

Within this project, our lab is hence developing novel ways for processing “fast Big Data”, i.e., processing of analytical queries where the underlying data is constantly being updated. The analytics problems envisioned cover wide areas of computer science and include database aggregate queries, probabilistic inference, matrix chain computation, and building statistical models.

The objective of this master thesis is to build upon the novel dynamic processing algorithms being developed in the lab, and complement these algorithms by proposing dynamic evaluation algorithms that execute on modern GPU architectures, thereby exploiting their massive parallel processing capabilities.

Since our current development is done in the Scala programming language, prospective students should either know Scala, or being willing to learn it within the context of the master thesis.

Validation of the approach Validation of master thesis' work should be done on two levels:

  • a theoretical level; by proposing and discussing alternative ways to do incremental computation on GPU architectures, and comparing these from a theoretical complexity viewpoint
  • an experimental level; by proposing a benchmark collection of CEP queries that can be used to test the obtained versions of the interpreter/compiler, and report on the experimentally observed performance on this benchmark.

Deliverables of the master thesis project

  • An overview of query processing on GPUs
  • A definition of the analytics queries under consideration
  • A description of different possible dynamic evaluation algorithms for the analytical queries on GPU architectures.
  • A theoretical comparison of these possibilities
  • The implementaiton of the evaluation algorithm(s) (as an interpreter/compiler)
  • A benchmark set of queries and associated data sets for the experimental validation
  • An experimental validation of the compiler, and analysis of the results.

Interested? Contact : Stijn Vansummeren

Status: available

Multi-query Optimization in Spark

Distributed computing platforms such as Hadoop and Spark focus on addressing the following challenges in large systems: (1) latency, (2) scalability, and (3) fault tolerance. Dedicating computing resources for each application executed by Spark can lead to a waste of resources. Unified distributed file systems such as Alluxio has provided a platform for computing results among simultaneously running applications. However, it is up to the developers to decide on what to share.

The objective of this master thesis is to optimize various applications running on a Spark platform, optimize their execution plans by autonomously finding sharing opportunities, namely finding the RDDs that can be shared among these applications, and computing these shared plans once instead of multiple times for each query.

Deliverables of the master thesis project

  • An overview of the Apache Spark architecture.
  • Develop a performance model for queries executed by Spark.
  • An implementation that optimizes queries executed by Spark and identify sharing opportunities.
  • An experimental validation of the developed system.

Interested? Contact : Iman Elghandour or Stijn Vansummeren

Status: available

Accelerated Distributed Platform for Spatial Queries

It is now common to query terabytes of spatial data. Several new frameworks extend distributed computing platforms such as Hadoop and Spark to enable them to efficiently process spatial queries by providing (1) mechanisms to efficiently store spatial data and index them ; and (2) packages of built in spatial operations for these platforms. Meanwhile, it is now common to accelerate Hadoop and Spark using accelerators such as GPUs and FPGAs.

The objective of this master thesis is to build a framework that efficiently executes spatial queries on a Spark version that is enabled to run its tasks on GPUs.

Deliverables of the master thesis project

  • An overview of Spatial queries and frameworks for processing big spatial data.
  • A study of best approaches to represent spatial data while it is queried by Spark and GPUs.
  • An implementation of common spatial operations and computational geometry algorithm on GPUs and Spark.
  • An experimental validation of the developed system.

Interested? Contact : Iman Elghandour or Stijn Vansummeren

Status: available

Co-locating Big Spatial Data Stored in HDFS

Spatial databases employ spatial indexes to speedup the access of spatial data. New frameworks are introduced to build such indexes for Hadoop and Spark. However, there are not fully integrated on the file system level.

The objective of this master thesis is to build these indexes within the layer of HDFS and use this implementation to co-locate files that are typically accessed together by the spatial queries.

Deliverables of the master thesis project

  • An overview of spatial queries and frameworks for processing big spatial data.
  • A study of different types of indexes how they can be built in HDFS, and how we can use the replicas of HDFS to store multiple types of indexes
  • An implementation of spatial indexes in HDFS.
  • An experimental validation of the developed system.

Interested? * Contact : Iman Elghandour or Stijn Vansummeren

Status: available

Complex Event Processing in Apache Spark and Apache Storm

The master thesis is put forward in the context of the SPICES “Scalable Processing and mIning of Complex Events for Security-analytics” research project, funded by Innoviris.

Within this project, our lab is developping a declarative language for Complex Event Processing (CEP for short). The goal in Complex Event Processing is to derive pre-defined patterns in a stream of raw events. Raw events are typically sensor readings (such as “password incorrect for user X trying to log in on machine Y” or “file transfer from machine X to machine Y”). The goal of CEP is then to correlate these events into complex events. For example, repeated failed login attempts by X to Y should trigger a complex event “password cracking warning” that refers to all failed login attempts.

The objective of this master thesis is to build an interpreter/compiler for this declarative CEP language that targets the distributed computing frameworks Apache Spark and/or Apache Storm as backends. Getting aquaintend with these technologies is part of the master thesis objective.

Validation of the approach Validation of the proposed interpreter/compiler should be done on two levels:

  • a theoretical level; by comparing the generated Spark/Storm processors to a processor based on “Incremental computation” that is being developped at the lab
  • an experimental level; by proposing a benchmark collection of CEP queries that can be used to test the obtained interpreter/compiler, and report on the experimentally observed performance on this benchmark.

Deliverables of the master thesis project

  • An overview of the processing models of Spark and Storm
  • A definition of the declarative CEP language under consideration
  • A description of the interpretation/compilation algorithm
  • A theoretical comparison of this algorithm wrt an incremental evaluation algorithm.
  • The interpreter/compiler itself (software artifact)
  • A benchmark set of CEP queries and associated data sets for the experimental validation
  • An experimental validation of the compiler, and analysis of the results.


Status: available

Graph Indexing for Fast Subgraph Isomorphism Testing

There is an increasing amount of scientific data, mostly from the bio-medical sciences, that can be represented as collections of graphs (chemical molecules, gene interaction networks, …). A crucial operation when searching in this data is that of subgraph isomorphism testing: given a pattern P that one is interested in (also a graph) in and a collection D of graphs (e.g., chemical molecules), find all graphs in G that have P as a subgraph. Unfortunately, the subgraph isomorphism problem is computationally intractable. In ongoing research, to enable tractable processing of this problem, we aim to reduce the number of candidate graphs in D to which a subgraph isomorphism test needs to be executed. Specifically, we index the graphs in the collection D by means of decomposing them into graphs for which subgraph isomorphism *is* tractable. An associated algorithm that filters graphs that certainly cannot match P can then formulated based on ideas from information retrieval.

In this master thesis project, the student will emperically validate on real-world datasets the extent to which graphs can be decomposed into graphs for which subgraph isomorphism is tractable, and run experiments to validate the effectiveness of the proposed method in terms of filtering power.

Interested? Contact : Stijn Vansummeren

Status: available

Sentiment Analysis

The sentiment analysis task aims to detect subjective information polarity in the target text by applying Natural Language Processing (NLP), text analysis and computational linguistics techniques. With the emergence of web 2.0, it becomes easy for Internet users to post their opinionated comments and share their thoughts via social networks, forums and especially Twitter. With more resources and NLP tools becoming available and with the recent developed sentiment lexicons, sentiment analysis is having more attention from the research community. Nevertheless, Named Entities (NEs) effectiveness was not studied even though it is easily noticeable that social resources include many NEs. In ongoing research, we aim to investigate the effectiveness of Named Entities (person, location and organization entities) on sentiment analysis and dive beyond the Named Entities recognition to propose a framework of Named Entities polarity classification and process an empirical evaluation on their effectiveness on Sentiment classification.

In this master thesis project, the student will empirically validate on real-world datasets the effectiveness of Named Entities (person, location and organization entities) on sentiment analysis and run experiments on different languages (French, Dutch, English and German).

Interested? Contact : Hatem Haddad

Status: available

Publishing and Using Spatio-temporal Data on the Semantic Web

RDF is the W3C proposed framework for representing information in the Web. Basically, information in RDF is represented as a set of triples of the form (subject,predicate,object). RDF syntax is based on directed labeled graphs, where URIs are used as node labels and edge labels. The Linked Open Data (LOD) initiative is aimed at extending the Web by means of publishing various open datasets as RDF, setting RDF links between data items from different data sources. Many companies and government agencies are moving towards publishing data following the LOD initiative. In order to do this, the original data must be transformed into Linked Open Data. Although most of these data are alphanumerical, most of the time they contained a spatial or spatio-temporal component, that must also be transformed. This can be exploited by application providers, that can build attractive and useful applications, in particular, for devices like mobile phones, tablets, etc.

The goals of this thesis are: (1) study the existing proposals for mapping spatio-temporal data into LOD; (2) apply this mapping to a real-world case study (as was the case for the Open Semantic Cloud for Brussels project; (3) Based on the produced mapping, and using existing applications like the Linked Geo Data project, build applications that make use of LOD for example, to find out which cultural events are taking place at a given time at a given location.

Extending SPARQL for Spatio-temporal Data Support

SPARQL is the W3C standard language to query RDF data over the semantic web. Although syntactically similar to SQL, SPARQL is based on graph matching. In addition, SPARQL is aimed, basically, to query alphanumerical data. Therefore, a proposal to extend SPARQL to support spatial data, called GeoSPARQL, has been presented to the Open Geospatial Consortium.

In this thesis we propose to (1) perform an analysis of the current proposal for GeoSPARQL; (2) a study of current implementations of SPARQL that support spatial data; (3) implement simple extensions for SPARQL to support spatial data, and use these language in real-world use cases.

Efficient Management of (Sub-)structure Similarity Search Over Large Graph Databases.

The problem of (sub-)structure similarity search over graph data has recently drawn significant research interest due to its importance in many application areas such as in Bio-informatics, Chem-informatics, Social Network, Software Engineering, World Wide Web, Pattern Recognition, etc. Consider, for example, the area of drug design, efficient techniques are required to query and analyze huge data sets of chemical molecules thus shortening the discovery cycle in drug design and other scientific activities.

Graph edit distance is widely accepted as a similarity measure of labeled graphs due to its ability to cope with any kind of graph structures and labeling schemes. Today, graph edit similarity plays a significant role in managing graph data , and is employed in a variety of analysis tasks such as graph classification and clustering, object recognition in computer vision, etc.

In this master thesis project, due to the hardness of graph edit distance (computing graph edit distance is known to be NP-hard problem), the student will investigate the current approaches that deals with problem complexity while searching for similar (sub-)structures. At the end, the student should be able to empirically analyze and contrast some of the interesting approaches.

A Generic Similarity Measure For Symbolic Trajectories

Moving object databases (MOD) are database systems that can store and manage moving object data. A moving object is a value that changes over time. It can be spatial (e.g., a car driving on the road network), or non-spatial (e.g., the temperature in Brussels). Using a variety of sensors, the changing values of moving objects can be recorded in digital formats. A MOD, then, helps storing and querying such data. There are two types of MOD. The first is the trajectory database, that manages the history of movement. The second type, in contrast, manages the stream of current movement and the prediction of the near future. This thesis belongs to the first type (trajectory databases). The research in this area mainly goes around proposing data persistency models and query operations for trajectory data.

A sub-topic of MOD is the study of semantic trajectories. It is motivated by the fact that the semantic of the movement is lost during the observation process. You GPS logger, for instance, would record a sequence of (lon, lat, time) that describe your trajectory. It won't, however, store the purpose of your trip (work, leisure, …), the transportation mode (car, bus, on foot, …), and other semantics of your trip. Research works have accordingly emerged to extract semantics from the trajectory raw data, and to provide database persistency to semantic trajectories.

Recently, Ralf Güting et al. published a model called “symbolic trajectories”, which can be viewed as a representation of semantic trajectories: Ralf Hartmut Güting, Fabio Valdés, and Maria Luisa Damiani. 2015. Symbolic Trajectories. ACM Trans. Spatial Algorithms Syst. 1, 2, Article 7 (July 2015), 51 pages. A symbolic trajectory is a very simple structure composed of a sequence of pairs (time interval, label). So, it is a time dependent label, where every label can tell something about the semantics of the moving object during its associated time interval. We think this model is promising because of its simplicity and genericness.

The goal of this thesis is to implement a similarity operator for symbolic trajectories. There are three dimensions of similarity in symbolic trajectories: temporal similarity, value similarity, and semantic similarity. Such an operator should be flexible to express arbitrary combinations of them. It should accept a pair of semantic trajectories and return a numerical value that can be used for clustering or ranking objects based on their similarity. Symbolic trajectories are similar to time series, except that labels are annotated by time intervals, rather than time points. We think that the techniques of time series similarity can be adopted for symbolic trajectories. This thesis should assess that, and implement a similarity measure based on time series similarity. The implementation is required to be done as an extension to PostGIS. We have already implemented some temporal types and operations on top of PostGIS, where you can start from.

Deliverables of the master thesis project

  • Reporting on the state of art of semantic trajectory similarity measures.
  • Reporting on the state of art in time series similarity measures.
  • Assessing the application of time series similarity to symbolic trajectories.
  • Implementing symbolic trajectories on top of PostGIS.
  • Implementation and evaluating the proposed symbolic trajectory similarity operator.


Status: available

teaching/mfe/is.txt · Last modified: 2018/08/07 11:42 by ezimanyi