The analysis of social structures is important in many contexts, especially in Global Software Development, where various developers with diverse skills and knowledge are involved. In this sense, searching for essential members is a valuable task since they are fundamental to the network's evolution. With the main goal of identifying and monitoring these individuals, we propose a temporal analysis approach that explores syntactic and semantic network aspects. We describe experiments based on popular projects on Github that consider a network modeled over consecutive time periods. We also propose an ontology to represent the domain knowledge and explore the network by investigating its semantic context. We provide evidence that our approach can detect individuals considered essential based on their role in the network.