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Tree-based model editors and hybrid graphical-textual model editors have advantages and limitations when editing domain models. Data is displayed hierarchically in tree-based model editors, whereas hybrid graphical-textual model editors capture high-level domain concepts graphically and low-level domain details textually. We conducted an empirical user study with 22 participants to evaluate the implicit assumption of system modellers that hybrid notations are superior, and to investigate the tradeoffs between the default EMF-based tree model editor and a Sirius/Xtext-based hybrid model editor. The results of the user study indicate that users largely prefer the hybrid editor and are more confident with hybrid notations for understanding the meaning of conditions. Furthermore, we found that the tree editor provided superior performance for analysing ordered lists of model elements, whereas activities requiring the comprehension or modelling of complex conditions were carried out faster through the hybrid editor., Comment: 12 pages

Security can be seen as an optimisation objective in NoC resource management, and as such poses trade-offs against other objectives such as real-time schedulability. In this paper, we show how to increase NoC resilience against a concrete type of security attack, named side-channel attack, which exploit the correlation between specific non-functional properties (such as packet latencies and routes, in the case of NoCs) to infer the functional behaviour of secure applications. For instance, the transmission of a packet over a given link of the NoC may hint on a cache miss, which can be used by an attacker to guess specific parts of a secret cryptographic key, effectively weakening it. We therefore propose packet route randomisation as a mechanism to increase NoC resilience against side-channel attacks, focusing specifically on the potential impact of such an approach upon hard real-time systems, where schedulability is a vital design requirement. Using an evolutionary optimisation approach, we show how to effectively apply route randomisation in such a way that it can increase NoC security while controlling its impact on hard real-time performance guarantees. Extensive experimental evidence based on analytical and simulation models supports our findings.