Schema-aware Labelling of XML Documents for Efficient Query and Update Processing in SemCrypt

The increasing number and size of XML documents require efficient techniques for storing, querying and updating XML. When the privacy of XML documents is ensured by encryption, special query and update processing techniques have to compensate for the additional encryption overhead. This paper proposes a schema-aware labelling scheme which is used in SemCrypt to enable clients to query and update encrypted XML documents stored at insecure servers. Each node of an XML document is assigned a special label. By performing operations on these node labels, the client can navigate within XML documents and process single path, branching path and typed queries with a minimum number of accesses to the database server. Integrating schema information into labels further improves query performance and enables to efficiently query and update encrypted and non-encrypted XML documents.