Object-relational database systems process XML values in a way that preserves node identities of nodes in the XML values and perform node-id based operations more efficiently or even in circumstances where such operations were not performed. An object-relational database system represents an XML value as a serialized stream of bytes, herein referred to as a serialized image. A serialized image may represent an XML value of the XMLType that is stored and/or generated by an object-relational database system. The serialized image contains one or more node identifiers that identify nodes within the XML value. The serialized image may also contain a pointer to an in-memory representation of the XML value, allowing the in-memory representation to be accessed via the pointer without having re-create the in-memory representation.