arXiv subjects

Lucas Lima

Publications and source records attributed to Lucas Lima.

4 recordsLinked to original sources

arXiv2025

Model management to support systems engineering workflows using ontology-based knowledge graphs

System engineering has been shifting from document-centric to model-based approaches, where assets are becoming more and more digital. Although digitisation conveys several benefits, it also brings several concerns (e.g., storage and access) and opportunities. In the context of Cyber- Physical Systems (CPS), we have experts from various domains executing complex workflows and manipulating models in a plethora of different formalisms, each with their own methods, techniques and tools. Storing knowledge on these workflows can reduce considerable effort during system development not only to allow their repeatability and replicability but also to access and reason on data generated by their execution. In this work, we propose a framework to manage modelling artefacts generated from workflow executions. The basic workflow concepts, related formalisms and artefacts are formally defined in an ontology specified in OML (Ontology Modelling Language). This ontology enables the construction of a knowledge graph that contains system engineering data to which we can apply reasoning. We also developed several tools to support system engineering during the design of workflows, their enactment, and artefact storage, considering versioning, querying and reasoning on the stored data. These tools also hide the complexity of manipulating the knowledge graph directly. Finally, we have applied our proposed framework in a real-world system development scenario of a drivetrain smart sensor system. Results show that our proposal not only helped the system engineer with fundamental difficulties like storage and versioning but also reduced the time needed to access relevant information and new knowledge that can be inferred from the knowledge graph.

cs.SE↗

arXiv2025

Reasonable Experiments in Model-Based Systems Engineering

With the current trend in Model-Based Systems Engineering towards Digital Engineering and early Validation & Verification, experiments are increasingly used to estimate system parameters and explore design decisions. Managing such experimental configuration metadata and results is of utmost importance in accelerating overall design effort. In particular, we observe it is important to 'intelligent-ly' reuse experiment-related data to save time and effort by not performing potentially superfluous, time-consuming, and resource-intensive experiments. In this work, we present a framework for managing experiments on digital and/or physical assets with a focus on case-based reasoning with domain knowledge to reuse experimental data efficiently by deciding whether an already-performed experiment (or associated answer) can be reused to answer a new (potentially different) question from the engineer/user without having to set up and perform a new experiment. We provide the general architecture for such an experiment manager and validate our approach using an industrial vehicular energy system-design case study.

cs.SE↗

arXiv2019

A framework for verifying deadlock and nondeterminism in UML activity diagrams based on CSP

Deadlock and nondeterminism may become increasingly hard to detect in concurrent and distributed systems. UML activity diagrams are flowcharts that model sequential and concurrent behavior. Although the UML community widely adopts such diagrams, there is no standard approach to verify the presence of deadlock and nondeterministic behavior in activity diagrams. Nondeterminism is usually neglected in the literature even though it may be considered a very relevant property. This work proposes a framework for the automatic verification of deadlock and nondeterminism in UML activity diagrams. It introduces a compositional CSP semantics for activity diagrams that is used to automatically generate CSP specifications from UML models. These specifications are the input for the automatic verification of deadlock and nondeterministic behavior using the FDR refinement checker. We propose a plugin for the Astah modeling environment that mechanizes the translation process, and that calls FDR in the background to perform the verification of properties. The tool keeps the traceability between a diagram and its CSP specification. It parses the FDR results to highlight the diagram paths that lead to a deadlock or a nondeterministic behavior. This framework adds verification capabilities to the UML modeling tool and keeps the formal semantics transparent to the users. Therefore, the user does not need to understand or manipulate formal notations during modeling. We present the results of a case study that applies the proposed framework for the verification of models in the domain of cloud computing. We discuss future applications due to the potential of our approach.

cs.SE↗

arXiv2018

Inside the Right-Leaning Echo Chambers: Characterizing Gab, an Unmoderated Social System

The moderation of content in many social media systems, such as Twitter and Facebook, motivated the emergence of a new social network system that promotes free speech, named Gab. Soon after that, Gab has been removed from Google Play Store for violating the company's hate speech policy and it has been rejected by Apple for similar reasons. In this paper we characterize Gab, aiming at understanding who are the users who joined it and what kind of content they share in this system. Our findings show that Gab is a very politically oriented system that hosts banned users from other social networks, some of them due to possible cases of hate speech and association with extremism. We provide the first measurement of news dissemination inside a right-leaning echo chamber, investigating a social media where readers are rarely exposed to content that cuts across ideological lines, but rather are fed with content that reinforces their current political or social views.

cs.SI↗