Pandora's memory was originally stored in an XML file. There was also a memory plug-in that uses Java serialization. Her memory is now stored in a database, but XML should still be plugable. The XML memory format can also be used to interchange knowledge files between Pandora instances.
The XML memory stores each memory vertex as an element, and each relationship as an element, relating the source and target ids.
The XSD that defines the XML format for the memory is here.
You can view an example of Pandora's memory here.