Pub. online:16 Jun 2022Type:Research ArticleOpen Access
Volume 33, Issue 2 (2022), pp. 343–364
Knowledge graphs are commonly represented by ontology-based databases. Tracking the provenance of ontological changes and ensuring ontology consistency is important. In this work, we propose a transaction manager for ontology-based database manipulation that combines blockchain and Semantic Web technologies. The latter is used for the efficient querying and modification of data, whereas the blockchain is used for the secure storage and tracking of changes. The blockchain enables a decentralized setup and data restoration. We evaluate our solution by measuring cost and time. Our solution introduces some overhead for updates whereas querying works at the same speed as the underlying ontology database.
Pub. online:1 Jan 2017Type:Research ArticleOpen Access
Volume 28, Issue 1 (2017), pp. 23–44
Computational thinking is an increasingly important focus in computer science or informatics curricula around the world, and ways of incorporating it into the school curricula are being sought. The Bebras contest on informatics, which originated 12 years ago and now involves around 50 countries, consists of short problem-solving tasks based on topics in informatics. Bebras tasks engender the development of computational thinking skills by incorporating abstraction, algorithmic thinking, decomposition, evaluation and generalization. Bebras tasks cover a range of informatics concepts including algorithms and data structures, programming, networking, databases and social and ethical issues. Having built up a substantial number of Bebras tasks over 12 years it is important to be able to categorize them so that they can be easily accessed by the Bebras community and teachers within schools. The categorization of tasks within Bebras is important as it ensures that tasks span a wide range of topics; there have been several categorization schemes suggested to date. In this paper we present a new two-dimensional categorization system that takes account of computational thinking skills as well as content knowledge. Examples are given from recent tasks that illustrate the role that Bebras can play in the development of computational thinking skills.