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Having described the basics of how cuts and variables are stored and accessed, we now describe how the search tree nodes are stored. Since the base constraints and variables are present in every LP relaxation, only the indices of the extra constraints and variables are stored in each node's description. A complete description of the current basis is maintained to allow a warm start to the computation in each search node. This basis is either inherited from the parent, computed during strong branching (see Section 5.2.3), or comes from earlier partial processing of the node itself (see Section 5.3.2). Because the set of active variables and the status of the basis do not tend to change much from parent to child, all of these data are stored as differences with respect to the parent when that description is smaller than the explicit one would be.