However, this does not mean that you have to store the value as a compound object that contains many strings. In fact, this strikes me as a rather cumbersome approach that would make it harder to use the data. In SMW we store URIs as one string. Splitting this string into parts (under the assumption that it was a well-formed URL to start with) is quite easy, if this is needed (SMW does this). Conclusion: the use of a datatype for IRIs is in no way tied to the use of an impractical serialisation; reference implementations exist.