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#95: Development of CF 1.5 Data Model -----------------------------+---------------------------------------------- Reporter: markh | Owner: [email protected] Type: task | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by mgschultz): Dear all, so, if I understand correctly, then the issue is essentially whether or not to have a concept like "global attributes" in the CF data model. I would argue in favor of this, and generally in favor of supporting some sort of hierarchy in the data model. There are reasons why HDF5 or netCDF4 allow for groups, and why global attributes were allowed in the first place. Also, any kind of XML metadata are hierarchical. Don't namespaces offer a solution here? If we allow for a hierarchy of field constructs and attributes, then the rule "local overwrites global" can be implemented quite naturally, one can move attributes up or down the hierarchy level (up will require some rules), and thus the "encoding" of the data in a specific file format should create little problems. Without recognition of hierarchy levels there will be many more problems, I believe. Perhaps it is also useful to discuss this with an example: assume you have N models generating M data sets each from X experiments. Clearly there are metadata which are specific to a variable from the output of one experiment, metadata describing an experiment, others which are specific for a model, and finally some generic metadata describing the project, data center, etc. All of this can be reflected in a hierarchical model, but I fear that things (in particular changes) would easily get lost if all attributes are maintained at the variable level only. An alternative way would be to allow for "independent" attributes which can be defined outside any field construct, and to allow field constriuct attributes to be links to such independent attributes. Note that this still doesn't mean a 1:1 reflection of the netcdf global attributes model, because it may be that some field constructs share one independent attribute and another set of field constructs shares another independent attribute with the same name. Best regards, Martin -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/95#comment:68> CF Metadata <http://cf-pcmdi.llnl.gov/> CF Metadata This message came from the CF Trac system. To unsubscribe, without unsubscribing to the regular cf-metadata list, send a message to "[email protected]" with "unsubscribe cf-metadata" in the body of your message.
