This attribute indicates whether the particular family of view
subtrees is included or excluded in the SNMPv2 context's (or
SNMPv1 community's) MIB view.
The value 'includedSubtree' indicates that the corresponding
instances of subTree and mask define a family of view subtrees
included in the MIB view.
The value 'excludedSubtree' indicates that the corresponding
instances of subTree and mask define a family of view subtrees
excluded in the MIB view.