BES File Out NetCDF

How to flatten hierarchical types

For a structure such as

Structure {
    Int x;
    Int y;
} Point;

represent that as

Point.x
Point.y

Explicitly including the dot seems ugly and like a kludge and so on, but it means that the new variable name can be feed back into the server to get the data.

Because this is hardly a lossless, we should also add an attribute that contains the original real name of the variable - information that this is the result of a flattening operation, that the parent variable was a Structure, Sequence or Grid and its name was xyz. Given that, it should be easy to sort out how to make a future request for the data in the translated variable.

This in some way obviates the need for the dot, but I think we should use that regardless.

General questions

• Should I traverse the data structure to see if there are any sequences?

jimg 17:53, 18 December 2008 (PST) Yes. An initial version should note their presence and add an attribute noting that they have been elided. To translate a Sequence, there are several cases to consider:

1. A Sequence of simple types only (which means a one-level sequence): translate to a set of arrays using a name-prefix flattening scheme.
2. A nested sequence (otherwise with only simple types) should first be flattened to a one level sequence and then that should be flattened.
3. A Sequence with a Structure or Grid should be flattened by recursively applying the flattening logic to the components.

Structures

• Flatten
• prepend name of structure with an underscore followed by the variable name. Keep track as there might be embedded structures, grids, etc...

jimg 17:53, 18 December 2008 (PST) Use the procedure described above in How to flatten hierarchical types.

jimg 17:53, 18 December 2008 (PST) I would use a dot even though I know that dots in variable names are, in general, a bad idea. If we use underscores then it maybe hard for clients to form a name that can be used to access values from a server based on the information in the file.

Grid

• Flatten.
• Use the name of the grid for the array of values
• prepend the name of the grid plus an underscore to the names of each of the map vectors.

Array

• write_array appears to be working just fine.
• If array of complex types?

Sequences

• For now throw an exception

Attributes

• Global Attributes?
  • Include global attribute to include URL that generated that new file
• Variable Attributes
  • What about attributes for structures? Should these attributes be created for each of the variables in the structure? So, if there is a structure a with variables v1 and v2 then the attributes for a will be attributes for a_v1 and a_v2? Or are there attributes for each of the variables in the structure? Or both.
  • For multi-dimensional datasets there will be a structure for each container, and each of these containers will have global attributes.