Metadata secondary

Metadata are most easily provided in pick lists that appear as dropdown menns in the nser interface. New files in the system wonld typically receive mnltiple metadata. To stay with the previous example, each new metabolite would receive metadata for Species, Matrix, Tissue, and so forth. There are certain cases in which previously selected metadata (primary metadata) may affect the number of entries in a pick list of other metadata (secondary metadata). Selecting the primary metadata would then lead to exclusion of several nonapplicable secondary metadata or exclusion of an entire meta-key. 

Some of these secondary metadata may be shared by both primary metadata, and some of them are individually used for just one primary metadata. For instance, a blood sample can be taken from a living animal, and there might be a chance to take a sample of liver tissue without significantly harming the animal however, taking a sample of nerve tissue is usually not possible without killing the animal. That is, the combination of In Vivo with Whole Blood and Liver makes sense, whereas for In Vitro all the tissues apply. 

A solution is the definition of dependencies between metadata, which has consequences on the input of metadata if an object is created or uploaded. If a value is selected from the pick list for any metadata defined as primary data, available values for the secondary metadata are modified — usually reduced — according to the definition of dependencies. If only a single value remains to be valid for secondary data, the corresponding value is automatically selected. 

---