Welcome to my homepage! My name is Yannis Koltsidas and I am third-year Ph.D.student in the Database Group in the School of Informatics at the University of Edinburgh . My research interests lie primarily in the area of storage systems and system aspects of database systems. Particularly, I am interested in systems that employ novel storage media, such as NAND flash disks and use novel algorithms and data structures to boost I/O performance. I am also interested in archiving of scientific data and management of hierarchical data in general. My supervisor is Prof. Stratis Viglas. I completed my undergraduate studies at the Electrical and Computer Engineering Department of the NTUA in Athens, Greece, where I majored in Computer Science. My diploma thesis was in the area of Spatial Indexing and Profile Matching for Location Based Services under the supervision of Prof. Timos Sellis.

News

• 12/05/2008 : I am spending the summer at the IBM Almaden Research Center as an intern, working on storage systems for cloud computing applications.

Projects

• Flash-enabled storage systems. Design and implementation of a storage manager and a buffer manager for systems equipped with both a magnetic and a flash disk. The storage manager places data pages on one of the two disks only, according to their workload to achieve maximum efficiency. The buffer manager takes advantage of the asymmetric properties of the two types of storage media to reduce the total I/O cost of the system. The system has been implemented in C++ and does raw I/O on both disks. It can be used as a storage and buffer manager for a database system, as well as a filesystem that handles both disks transparently. Code here (currently in alpha).
• Hardware Failure Monitoring in Large Clusters. Research carried out during my internship at the IBM Almaden Research Center. Designed and developed FailMon, a system for detecting hardware failures in large clusters running the Apache Hadoop MapReduce Framework. FailMon operates in a distributed fashion and utilizes system and application log files, in addition to standard operating system utilities, to detect hardware failures. The code was contributed to the Hadoop community, via the Apache Software Foundation.
• Scientific Data Archiving. Implementation of the archiving techinques for hierarchical scientific data proposed by Buneman et al. (link). A brief description can be found here (see Chapter 3), while the application can be downloaded here. Requires Java 5.
• Sorting Hiearachical Data. Sorting Hierarchical Data in External Memory using HErMeS, a hierarchy-aware variation of merge-sort described here (see Chapter 4). The purpose of this project is to provide sorted inputs to the merge operator proposed by Buneman et al. (see above), thereby making the archiving process much more efficient. The implementation can be downloaded here (in C).
• Spatiotemporal Indexing and Profile Matching. Research carried out for my diploma thesis in the area of indexing for large-scale Location Based Services, under the supervision of Prof. Timos Sellis. A novel index was proposed for database systems to index moving users not only by their spatial position at a given time, but also by their set of profile preferences. The latter were expressed as a set of XPath queries. Research resulted in the development of a system that can efficiently answer queries regarding both the spatial position and the content preferences of users.

Publications

• Ioannis Koltsidas, Stratis Viglas
  Utility-Aware Multi-Device Caching
  Submitted for publication
• Ioannis Koltsidas, Stratis Viglas
  Flash-Aware Multi-Level Caching
  Submitted for publication
• Ioannis Koltsidas, Stratis Viglas
  Flashing Up The Storage Layer (paper)
  VLDB 2008, Auckland, New Zealand
• Ioannis Koltsidas, Heiko Müller, Stratis Viglas
  Sorting Hierarchical Data In External Memory For Archiving (paper)
  VLDB 2008, Auckland, New Zealand
• Heiko Müller, Peter Buneman, Ioannis Koltsidas
  XArch: Archiving Scientific and Reference Data (paper, poster)
  SIGMOD 2008, Vancouver, Canada (Demo paper)

Past Projects

This is a short list of projects I completed during my undergraduate studies. Unfortunately, most of them are only available in Greek.

• Diploma Thesis (with Panagiotis Papadimitriou): "Spatial and Profile Indexing for large-scale Location Based Services". Click here for the text (in Greek) and here for the source code requires Java 5). A short paper (19 pages) in English can be found here. You can also download the thesis presentation and the demo application.
• Edsger Compiler, for the Compilers course at NTUA, implemented in C++. Compiles a subset of C into x86 assembly code (with Panagiotis Papadimitriou).
• Hospital Information System. An information system that handles patients' appointments in a hospital, developed for the Design of Information Systems course at NTUA. Implemented in JSP using Oracle JDeveloper & Application Server with Oracle Database 10g Express.
• Base Station Maintenance application for the Software Engineering course at NTUA (with Panagiotis Papadimitriou). To be used by field technicians that perform maintenance operations to cellular network components (antennas etc.). The client application runs on PDA's and mobile phones and was developed using the .NET framework for wireless devices. The server consists of a database and an application server.
• Connect Four. An implementation for the popular game for the Artificial Intelligence course at NTUA. Includes graphical user interface and a powerful AI client. Written in Java.
• Warehouse management database, application server and graphical user interface client. Developed (with Panagiotis Papadimitriou) in .NET for the Introduction to Databases course at NTUA. Download here.

Working/Teaching Experience

• Teaching Assistant for the course "Advanced Databases" (University of Edinburgh, 2009)
• Research Intern at the IBM Almaden Research Center, working in the Storage Analytics and Resiliency group (2008).
• Research Associate of at the R&D of OTE S.A. (Greek PTT) involved in evaluation, testing and deploying IPTV solutions, supervised by Dr. Costantinos Boukouvalas (2005).
• Teaching Assistant in the undergraduate courses Introduction to Programming and Programming Techniques, academic years 2002-2005.
• Trainer Assistant in teachers' training course "Use of Information and Communication Technologies in Education".

Links

(under construction ;)