Metadata access order isn't declared and resolved

[m-fila]

Currently the access to metadata isn't being declared and resolved. For instance a result of two algorithms accessing the same metadata during initialize, the first writing and the second reading the same parameter, depends on the order of their initialization which we don't control directly.
This might not be happening now but probably something worth being aware of.

[tmadlener]

It could be considered a configuration error / problem if the same parameter is set multiple times IMO. Maybe the metadata service can be configured to check this?

[m-fila]

My original concern was more about that an algorithm writing the parameter could be initialized by the framework after an algorithm reading it.

[tmadlener]

Ah right, I haven't thought about that. Not entirely sure how to handle that best. Setting the parameters on the Frame is thread safe, we could check if all algorithms that set a parameter set it to the same value? Then the order wouldn't matter too much in the end. And arguably, it is still a potential issue if several algorithms set the same parameter to different values in which case we could still throw an exception or signal a failure.