  Schramm-Loewner Evolutions (SLEs) describe a one-parameter family of growth
processes in the plane that have particular conformal invariance properties.
For instance, SLE can define simple random curves in a simply connected domain.
In this paper we are interested in questions pertaining to the definition of
several SLEs in a domain (i.e. several random curves). In particular, one
derives infinitesimal commutation conditions, discuss some elementary
solutions, study integrability conditions following from commutation and show
how to lift these infinitesimal relations to global relations in simple cases.
The situation in multiply-connected domains is also discussed.
