Extensible and Self-Hosted — the interface and capabilities of Bespin should be highly extensible and easily accessible to users through Ubiquity-like commands or via the plug-in API.

XML has emerged as the standard of meta language representing data format. It is rich, clear, extensible and self-description. All advantages make it the best candidate for representing data model.

Moreover, components and composite components are self-described with extensible markup language (XML), and the latter are used as the containe.