Parameters/Metadata stored in EMData Objects
The EMData object, and its representation on disk in the BDB local database, XML files, and when serialized in Python using 'pickle', supports the concept of arbitrary header parameters also known as metadata. This metadata are key/value pairs. The keys are always simple ascii text, and the values may be virtually anything represented as an EMObject, including simple ints, floats and strings, as well as more complicated objects such as Transform classes. If an EMData object is stored in some fashion other than the 3 mechanisms above, some loss of metadata is almost guaranteed. The file i/o objects will try to preserve some of the basic metadata, but most of the cryoEM formats simply don't support arbitrary header-data. The EMAN2 convention is to use BDB for most internal purposes, and to use HDF5 for data transfer/exchange.
This page will serve as a repository for the officially supported parameter key/value pairs. While you are free to set any metadata keys/values you like in an EMData object, the names listed here may be interpreted in specific ways by specific modules within EMAN, so it would be unwise to abuse them. Also, if you make up your own name for some purpose, it wouldn't hurt to register it here in the 'unofficial' section, to avoid it being used by someone else for a different purpose.
Official tags (used in EMAN2/SPARX as distributed):
Unofficial tags (used by someone in their own code or for testing):