 Another consideration is compatibility with relativistic causal structure. See Myrvold (2021) for an overview of relavistic constraints on approaches to the measurement problem.The de Broglie-Bohm theory requires a distinguished relation of distant simultaneity for its formulation, and, it can be argued, this is an ineliminable feature of any hidden-variables theory of this sort, that selects some observable to always have definite values (see Berndl et al. 1996; Myrvold 2002, 2021). On the other hand, there are collapse models that are fully relativistic. On such models, collapses are localized events. Though probabilities of collapses at spacelike separation from each other are not independent, this probabilistic dependence does not require us to single one out as earlier and the other later. Thus, such theories do not require a distinguished relation of distant simultaneity. There remains, however, some discussion of how to equip such theories with beables (or “elements of reality”). See the entry on  collapse theories  and references therein; see also, for some recent contributions to the discussion, Fleming (2016), Maudlin (2016), and Myrvold (2016).  In the case of Everettian theories, one must first think about how to formulate the question of relativistic locality. Several authors have approached this issue in somewhat different ways, with a common conclusion that Everettian quantum mechanics is, indeed, local. (See Vaidman 1994; Bacciagaluppi 2002; Chapter 8 of Wallace 2012; Tipler 2014; Vaidman 2016; and Brown and Timpson 2016.)