Petri net has been widely used for modeling software systems due to its mathematical soundness and support of various tools. In many cases, performance-related analyses of Petri net for a software system need to consider the resource limitations caused by a specific platform. In terms of aspect-oriented approach, the interference of various resources scattered across a software system can be regarded as a specific concern that is only necessary during its performance-related analysis process. To capture the interactions of resources within the Petri net-based software architectural model, we propose an aspect-oriented resource composition model and the XML-based representation language called the resource extension markup language (ReML) for its description. In our approach, one or more resource composition models can be developed and described in ReML separately from the development of base software architectural models. Through the weaving process, a resource composition model can be applied to extend several Petri net-based software architectural models. The resource weaver generates an augmented Petri net used for analyzing performance characteristics of the extended software architectural model with resource interactions. Our aspect-oriented approach facilitates selecting an optimal or superior resource composition model for a software architectural model, and vice versa, which is illustrated using two exemplary server models.