I earned a computer science doctorate from the University of Karlsruhe (TH) in 2009, then was a post-doctoral research fellow at the University of Pretoria. In 2011, I joined TWT GmbH Science and Innovation. At present, I am a professor of computer science at Duale Hochschule Sachsen, Leipzig.
On this site you will find information about my professional and academic work. I am interested in programming, artificial intelligence, and data science.
I authored the Zhi# programming language - the first object-oriented programming language with inherent support for ontologies.
I am a member of ACM, IEEE Computer Society, and Gesellschaft für Informatik.
Since 1995, I support the exploration of the Solar System, the search for near-Earth objects, and the search for extraterrestrial life as a member of The Planetary Society.
2025 Symposium on Languages, Applications and Technologies (SLATE 2025), Faro, Portugal.
2025 International Computer Programming Education Conference (ICPEC 2025), Porto, Portugal.
2025 TEK-UP Digital Congress, Hammamet, Tunisia.
2024 Symposium on Languages, Applications and Technologies (SLATE 2024), Águeda, Portugal.
2024 International Computer Programming Education Conference (ICPEC 2024), Lisbon, Portugal.
2023 Symposium on Languages, Applications and Technologies (SLATE 2023), Vila do Conde, Portugal.
2023 International Computer Programming Education Conference (ICPEC 2023), Vila do Conde, Portugal.
2022 Studierendenkonferenz Informatik (SKILL 2022), Hamburg, Germany.
2022 INForum 2022: 13º Simpósio de Informática (INForum 2022), Guarda, Portugal.
2022 Symposium on Languages, Applications and Technologies (SLATE 2022), Covilhã, Portugal.
2022 International Computer Programming Education Conference (ICPEC 2022), Barcelos, Portugal.
2021 Symposium on Languages, Applications and Technologies (SLATE 2021), Argivai, Portugal.
2021 International Computer Programming Education Conference (ICPEC 2021), Braga, Portugal.
2020 Studierendenkonferenz Informatik (SKILL 2020), Karlsruhe, Germany.
2020 Symposium on Languages, Applications and Technologies (SLATE 2020), Barcelos, Portugal.
2020 International Conference on Cloud Computing and Services Science (CLOSER 2020), Prague, Czech Republic.
2020 International Computer Programming Education Conference (ICPEC 2020), Vila do Conde, Portugal.
2019 Symposium on Languages, Applications and Technologies (SLATE 2019), Coimbra, Portugal.
2018 Symposium on Languages, Applications and Technologies (SLATE 2018), Guimarães, Portugal.
2017 Workshop on Gamification Software for Education and Enterprises (FedCSIS 2017), Prague, Czech Republic.
2017 Digital Enterprise Computing 2017 (DEC 2017), Herman Hollerith Lehr- und Forschungszentrum (HHZ), Böblingen, Germany. Program Chair Cognitive Computing Track.
2017 Symposium on Languages, Applications and Technologies (SLATE 2017), Porto, Portugal.
2017 Workshop Industrial Applications of Artificial Intelligence (IAAI 2017), Stuttgart, Germany. Program Chair.
2016 International Conference on Emerging Networks and Systems Intelligence (EMERGING 2016), Porto, Portugal.
2016 International Conference on Ambient Computing, Applications, Services and Technologies (AMBIENT 2016), Venice, Italy.
2016 Symposium on Languages, Applications and Technologies (SLATE 2016), Maribor, Slovenia.
2016 International Conference on Cloud Computing and Services Science (CLOSER 2016), Rome, Italy.
2016 Praxisforum at Modellierung (Modellierung 2016), Karlsruhe, Germany. Program Chair.
2016 Editorial Advisory Board of the book "Gamification-Based E-Learning Strategies for Computer Programming Education" to be published by IGI Global.
2015 International Conference on Cloud Computing and Services Science (CLOSER 2015), Lisbon, Portugal.
2015 Symposium on Languages, Applications and Technologies (SLATE 2015), Madrid, Spain.
2015 International Conference on Cloud Computing, Grids, and Virtualization (CLOUD COMPUTING 2014), Nice, France.
2014 GI Workshop Technologien zur Analyse und Steuerung komplexer cyber-physischer Systeme (CPSData 2014), Stuttgart, Deutschland.
2014 Informatiktage (INFORMATIKTAGE 2014), Potsdam, Germany.
2014 Innovative Teaching Strategies and New Learning Paradigms in Computer Programming, IGI GLOBAL (editorial advisory board).
2014 Symposium on Languages, Applications and Technologies (SLATE 2014), Braga, Portugal.
2014 International Conference on Cloud Computing and Services Science (CLOSER 2014), Barcelona, Spain.
2014 International Conference on Cloud Computing, Grids, and Virtualization (CLOUD COMPUTING 2014), Barcelona, Spain.
2013 Symposium on Languages, Applications and Technologies (SLATE 2013), Porto, Portugal.
2013 International Conference on Ambient Computing, Applications, Services and Technologies (AMBIENT 2013), Porto, Portugal.
2013 International Conference on Ambient Systems, Networks and Technologies (ANT 2013), Halifax, Nova Scotia, Canada.
2013 International Conference on Cloud Computing and Services Science (CLOSER 2013), Aachen, Germany.
2012 Workshop on Programming the Semantic Web (PSW 2012), Boston, USA.
2012 International Conference on Ambient Systems, Networks and Technologies (ANT 2012), Niagara Falls, Ontario, Canada.
2012 Symposium on Languages, Applications and Technologies (SLATE 2012), Braga, Portugal.
2012 International Workshop on Web APIs and Services Mashups (Mashups 2012), Bertinoro, Italy.
2012 International Conference on Cloud Computing and Services Science (CLOSER 2012), Porto, Portugal.
2011 National Conference on XML and its Applications (XATA 2011), Vila do Conde, Portugal. Editorial Advisory Board of the book "Innovations in XML Applications and Metadata Management: Advancing Technologies".
2011 International Workshop on Web APIs and Services Mashups (Mashups 2011), Lugano, Switzerland.
2011 International Conference on Cloud Computing and Services Science (CLOSER 2011), Noordwijkerhout, The Netherlands.
2010 International Workshop on Web APIs and Services Mashups (Mashups 2010), Ayia Napa, Cyprus.
2010 International Conference on Cloud Computing and Services Science (CLOSER 2010), Valencia, Spain.
2010 Workshop on Transforming and Weaving Ontologies in Model Driven Engineering (TWOMDE 2010), Malaga, Spain.
2010 International Workshop on Modeling and Visualization of XML and Semantic Web Data (MoViX 2010), Bilbao, Spain.
2010 International Workshop on Benchmarking of XML and Semantic Web Applications (BenchmarX 2010), Tsukuba, Japan.
2009 Workshop on Transforming and Weaving Ontologies in Model Driven Engineering (TWOMDE 2009), Toulouse, France.
2009 International Workshop on Schema Languages for XML (X-Schemas 2009), Riga, Latvia.
2009 International Workshop on Modeling and Visualization of XML and Semantic Web Data (MoViX 2009), Linz, Austria.
2009 International Workshop on Benchmarking of XML and Semantic Web Applications (BenchmarX 2009), Brisbane, Australia.
2008 Workshop on Transforming and Weaving Ontologies in Model Driven Engineering (TWOMDE 2008), Toulouse, France.
2006 Workshop on Meta-modeling and Ontologies (WoMM 2006), Karlsruhe, Germany.
2022 Studierendenkonferenz Informatik (SKILL 2022), Hamburg, Germany.
2016 Stefan Wagner, Asim Abdulkhaleq, Kamer Kaya, and Alexander Paar. On the relationship of inconsistent software clones and faults: An empirical study. In SANER '16: Proceedings of the 23rd IEEE International Conference on Software Analysis, Evolution, and Reengineering, 2016.
Code cloning - copying and reusing pieces of source code - is a common phenomenon in software development in practice. There have been several empirical studies on the effects of cloning, but there are contradictory results regarding the connection of cloning and faults. Objective: Our aim is to clarify the relationship between code clones and faults. In particular, we focus on inconsistent (or type-3) clones in this work. Method: We conducted a case study with TWT GmbH Science & Innovation where we detected the code clones in three Java systems, set them into relation to information from issue tracking and version control and interviewed three key developers. Results: Of the type-3 clones, 17 % contain faults. Developers modified most of the type-3 clones simultaneously and thereby fixed half of the faults in type-3 clones consistently. Type-2 clones with faults all evolved to fixed type-3 clones. Clone length is significantly correlated with faultiness. Conclusion: There are indications that the developers in two cases have been aware of clones. It might be a reason for the weak relationship between type-3 clones and faults. Hence, it seems important to keep developers aware of clones, potentially with new tool support. Future studies need to investigate if the rate of faults in type-3 clones justifies using them as cues in defect detection.
2011 Alexander Paar and Denny Vrandečić. Zhi# - OWL aware compilation. In Grigoris Antoniou, Marko Grobelnik, Elena Paslaru Bontas Simperl, Bijan Parsia, Dimitris Plexousakis, Pieter De Leenheer, and Jeff Z. Pan, editors, ESWC '11: Proceedings of the 8th Extended Semantic Web Conference, volume 6644 of Lecture Notes in Computer Science, pages 315-329. Springer Verlag Berlin, Heidelberg, 06 2011.
The usefulness of the Web Ontology Language to describe domains of discourse and to facilitate automatic reasoning services has been widely acknowledged. However, the programmability of ontological knowledge bases is severely impaired by the different conceptual bases of statically typed object-oriented programming languages such as Java and C# and ontology languages such as the Web Ontology Language (OWL). In this work, a novel programming language is presented that integrates OWL and XSD data types with C#. The Zhi# programming language is the first solution of its kind to make XSD data types and OWL class descriptions first-class citizens of a widely-used programming language. The Zhi# programming language eases the development of Semantic Web applications and facilitates the use and reuse of knowledge in form of ontologies. The presented approach was successfully validated to reduce the number of possible runtime errors compared to the use of XML and OWL APIs.
2009 Alexander Paar and Jürgen Reuter. Computers in the Human Interaction Loop, chapter Ontological Modeling and Reasoning, pages 325-340. Human-Computer Interaction Series. Springer Verlag London, 04 2009.
A major challenge in putting the CHIL vision into practice was to integrate contributions from project partners all over Europe and the United States. While standard Web technologies such as HTTP support core data exchange, perceptual component integration places higher demands on distributed intercommunication. Interfaces have to be defined for the type-safe exchange of structured data between components that are implemented in diverse computer languages.
2006 Alexander Paar and Walter F. Tichy. Programming language inherent support for constrained XML Schema Definition data types and OWL DL. In ASE '06: Proceedings of the 21st IEEE/ACM International Conference on Automated Software Engineering, pages 281-284, Los Alamitos, CA, USA, 09 2006. IEEE Computer Society, IEEE Computer Society.
Recently, the Web Ontology Language (OWL) and XML Schema Definition (XSD) have become ever more important when it comes to conceptualize knowledge and to define programming language independent type systems. However, writing software that operates on ontological data and on XML instance documents still suffers from a lack of compile time support for OWL and XSD. Especially, obeying lexical- and value space constraints that may be imposed on XSD simple data types and preserving the consistency of assertional ontological knowledge is still error prone and laborious. Validating XML instance documents and checking the consistency of ontological knowledge bases according to given XML Schema Definitions and ontological terminologies, respectively, requires significant amounts of code. This paper presents novel compile time- and code generation features, which were implemented as an extension of the C# programming language. Zhi# provides compile time and runtime support for constrained XML Schema Definition simple data types and it guarantees terminological validity for modifications of assertional ontological data.
2003 Fridtjof Feldbusch, Alexander Paar, Manuel Odendahl, and Ivan Ivanov. The BTRC Bluetooth remote control system. Personal Ubiquitous Computing, 7(2):102-112, 07 2003.
Emerging radio technologies like WLAN and Bluetooth enable electronic devices of any kind to communicate with one another. A simple and easy to implement application layer protocol called BTRC protocol was developed allowing devices to exchange data of any kind and format over different protocols like TCP/IP or Bluetooth. Based upon this protocol a universal remote control system was implemented. Software applications simulating cellular phones and personal digital assistants (PDA) were developed as remote control devices. BTRC server devices send their graphical XML based user interface to the remote control. In this way, the use of household devices is simplified significantly.
2002 Manuel Lois Anido, Alexander Paar, and Nader Bagherzadeh. Improving the operation autonomy of SIMD processing elements by using guarded instructions and pseudo branches. In Martyn Edwards, editor, DSD '02: Proceedings of the Euromicro Symposium on Digital Systems Design, volume 0, page 148, Washington, DC, USA, 09 2002. IEEE Computer Society, IEEE Computer Society.
This paper presents a novel method for improving the operation autonomy of the processing elements (PE) of SIMD-like machines. By combining guarded instructions and pseudo branches it is possible to achieve higher operation autonomy and higher instruction level parallelism than in previous SIMD/ASIMD architectures. The paper shows that it is feasible to avoid most branches and it is also possible to emulate conditional execution on the processing elements, either by using guarded instructions or by using pseudo branches, thus avoiding unnecessary intervention by the array control unit in data-dependant computations. Pseudo branches are used when it is not possible to use guarded instructions. Additionally, they also support the implementation of complex nested if-then-else constructs, improving the execution of irregular data-parallel applications. The paper also shows that the simplicity of the method allows it to be implemented both in fine-grain and coarse-grain SIMD/ASIMD architectures because it does not require significant additional silicon area. Finally, it is shown that pseudo branches can be used to control the power saving of those processing elements that have instructions nullified.
2002 Alexander Paar, Manuel Lois Anido, and Nader Bagherzadeh. A novel predication scheme for a SIMD system-on-chip. In Burkhard Monien and Rainer Feldmann, editors, Euro-Par '02: Proceedings of the 8th International Euro-Par Conference on Parallel Processing, volume 0, pages 834-843, London, UK, 08 2002.Springer-Verlag.
This paper presents a novel predication scheme that was applied to a SIMD system-on-chip. This approach was devised by improving and combining the unrestricted predication model and the guarded execution model. It is shown that significant execution autonomy is added to the SIMD processing elements and that the code size is reduced considerably. Finally, the implemented predication scheme is compared with predication schemes of general purpose processors, and it is shown that it enables more efficient if-conversion compilations than previous architectures.