A protocol describes a standardized procedure for doing something.
There are multiple types of protocols, corresponding to different
tables or actions in BASE. Some protocol types (mostly concerning
biomaterials) are system protocol types, required to exist and
not be modified by users. More protocol types can be created as
needed.
The standard protocol types are:
sampling, extraction, labeling, pooling, hybridization, printing,
scanning, feature extraction.
Custom protocol types are needed to describe user-defined events
in the array LIMS.
A protocol is of a single protocol type.
A protocol may be annotated.
A single file may be attached to a protocol.
[implementation note] There should be a dummy protocol
"none" for each system protocol type.