Summary: XML provides extensibility through a common syntax but leaves the interpretation of the information to the developer. Increasing modularity through the use of XML namespaces further increases developers’ workload as they struggle to interpret ever more complex data models. RDF leverages the syntactic extensibility of XML and the modularity of XML namespaces and additionally provides global extensibility through a common data model

PlaceTime is a URI space that will define URIs for instants and intervals in time as well as points and regions in space. You'll be able to address a particular time or place or a combination of the two.

The URIs themselves will be retrievable via HTTP and the RDF representations will contain enough information to provide conversion between different ways of measuring the same thing. For example, if you refer to a URI representing a date and time using the Gregorian calendar you'll be able to determine the same date and time in other ways of measuring time such as the Islamic calendar or the number of seconds since the UNIX epoch. You'll be able to determine coincident or nearby events no matter what measurement scheme was used.

It's going to be a long process, but I fully intend to make it as open as possible. All the code and content is freely available and contributions are extremely welcome!