We proposed a list data sharing model, which utilizes semantics expressed in DTD for concurrency control of shared XML trees. In this model, tree updating actions such as inserting/deleting subtrees are allowed only for the repetitive parts. The proposed model guarantees that the resulting XML tree is valid even when applying tree update actions concurrently. Also, a new multigranularity locking mechanism called list locking protocol is proposed. This protocol locks on the (index) list of repetitive children nodes, so it allows updates on the descendants when the node's child subtree is being deleted or inserted. This protocol is expected to show better accessibility with less number of locking objects compared to the other locking methods on XML data.