Hey Markus,

Thanks for the writeup. This clarified some things, at least for me.

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.

Agreed. The IriValue implementation is based on the SMW one, and retains this capability. Using serialize and unserialize will cause concaternation of the parts into one string, and then split them back up to a bunch before they are passed to the constructor.

We are currently not using this though. Instead we are using the two last methods here: https://github.com/wikimedia/mediawiki-extensions-DataValues/blob/eea0d0e194c8819215934dee219782d57d09704e/DataValues/src/IriValue.php#L243

So the solution to the problem at hand seems to be either to change these two methods to do the same as serialize and unserialize, or to simply not use these methods in our serialization process. The former approach is the most local and easy to implement, and given the urgency of this, the one I suggest going with.

(Somewhat different topic, mainly directed at the WD team itself:) It is however an indication that having these two methods in the DataValue implementations is not the best idea to begin with. This has been clear for some time, though in order to fix this, we effectively need to go with the second approach and implement proper serialization infrastructure for DataValues. That'd also fix a number of other problems and awkwardness the current approach is causing.


Jeroen De Dauw
Don't panic. Don't be evil. ~=[,,_,,]:3