GANYMEDE DBStore File Format *NOT CURRENT*

GANYMEDE's DBStore file is a simple self-describing object store. The DBStore contains a two-level data dictionary and a simple encoding of all objects defined in the DBStore. The database scheme is encoded into the database file, but can be changed by the schema editor built into the Admin Console.

In the DBStore, object types, field types, object instances and fields in object instances are all identified via numeric identifiers. There can be on the order of 32 thousand different types of objects defined in the database, with each type of object having its own numeric 'namespace'. This allows each type of object to have on the order of 2 billion different instances stored in the database. Likewise, for each object type, there can be on the order of 32 thousand fields defined.

GANYMEDE is being designed with the assumption that once an object is created, it retains sole ownership of its object number forever. This simplifying assumption allows us to use an object number as an 'invariant id', suitable for use as an inter-object reference pointer. All internal processing, event tracking, etc., will use these object identifiers.

All elements in the DBStore file are stored using the Java DataStream object's binary encoding. In particular, strings are not ASCII, but rather are UTF Unicode strings. UTF encoding incorporates the length of the string into the binary encoding, allowing for strings of arbitrary length using the full 64k character Unicode character set in a compact representation.

Here is how the file is laid out:

DBStore Header (including object type count)

Object Type Definition (including Field count)

Field Definition

Field Definition

...

Object Count

Object Data (including field count for this object)

Field Code

Field Data, one of the following

• Boolean Array
• Boolean
• Date Array
• Date
• Object Reference Array
• Object Reference
• Numeric Array
• Number
• String Array
• String
• Permission Matrix

Field Code

Field Data

..

Object Data (including field count for this object)

Field Code

Field Data

..

..

Object Type Definition (including field count)

..

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