Structure

Entries can be regarded as being organised in a tree structure (although a particular messaging client doesn't have to represent the message store to the user in this way). The parent of each entry is recorded in the index entry's details.

The following figure gives an example of how services are placed below a root entry. Folders and messages can be children of the services, and then, in turn, of other folders.

The structure means that an index entry must conform to certain rules to be considered valid:

• a non-service entry cannot be owned by root and must have its service ID field set

• a service entry must be owned by root and have the service ID of itself