  The starting point of this work is a framework allowing to model systems with
dynamic process creation, equipped with a procedure to detect symmetric
executions (ie., which differ only by the identities of processes). This allows
to reduce the state space, potentially to an exponentially smaller size, and,
because process identifiers are never reused, this also allows to reduce to
finite size some infinite state spaces. However, in this approach, the
procedure to detect symmetries does not allow for computationally efficient
algorithms, mainly because each newly computed state has to be compared with
every already reached state.
  In this paper, we propose a new approach to detect symmetries in this
framework that will solve this problem, thus enabling for efficient algorithms.
We formalise a canonical representation of states and identify a sufficient
condition on the analysed model that guarantees that every symmetry can be
detected. For the models that do not fall into this category, our approach is
still correct but does not guarantee a maximal reduction of state space.
