General Simplicity This should not require the addition of any substantial new software that might prove problematic to introduce on an operational server or risk compromising performance on older hardware. Lightweight application Reading a document should be a very low overhead on the server, preferably avoiding any such overheads as a database query or multiple filesystem accesses. Write operations should also be fast but are considered less critical. Extensibility Many planned capabilities are not yet implemented, but the design must accommodate introducing them at a later date without disrupting the existing site.