The design and development of experiments for virtual laboratories is a composite process, since the same virtual laboratory can be used by learners studying in a variety of educational institutions, including secondary education schools and universities. We used the Unified Modeling Language (UML) to model experiments so as to provide a standard graphical notation and enhance reusability. We, then, map the UML model to Petri nets (PN) as a step to formally verify the experimental procedures. Then, the similarity of these models is computed based on the simulation traces of the corresponding Petri nets and the log file produced by the experiment as executed in the virtual laboratory used. The example of a microscoping experiment applied in different educational settings is used for illustrating the proposed approach.