For implementing some of these features, the following additional search functionalities will be needed (if not available already):

• Make search widgets, that allow to filter for an additional property: E.g. show a histogram of all photon energies, where associated_source==source_pump, and another one where associated_source==source_probe
• Search for the existance of certain variadic instances (e.g. all entries with BEAM[beam_pump])
• Search for statistical attributes of array fields (e.g. min_value, max_value, mean_value, number_of_points, ...)
• Search widgets for ranges: Show a histogram of the number of datasets that contain data within a certain range. Normal histogram, but don't fill directly by values, but for each bin count each dataset where the bin value is in between two values from the dataset. (better ideas?)
• A periodic system table with mapping of elements to core level energies, and histogramming like above based on these energies.

For implementing some of these features, the following additional search functionalities will be needed (if not available already):

* [ ]  Make search widgets, that allow to filter for an additional property: E.g. show a histogram of all photon energies, where associated_source==source_pump, and another one where associated_source==source_probe[ ]  Search for the existance of certain variadic instances (e.g. all entries with BEAM[beam_pump])[ ]  

We decided now to at least for NXmpes include all relevant fields and groups that we would like to search for in the Appdef. With this solution, the first two issues are most likely not necessary anymore.