Dear Daniel Thanks. This is much better. "Search by absolute path" should start with "A" not "An". In "Search by relative path" I would say "(i.e. containing a slash but not with a leading slash e.g. `child/lat`)".
I think "Search by proximity" can be stated more concisely and perhaps more clearly with less repetition, thus: "A variable or dimension specified with no path (for example, `lat`) refers to the variable or dimension of that name, if there is one, in the referring group. If the variable or dimension is not in the referring group then it is termed an out-of-group reference. Out-of-group references are resolved by searching all direct ancestors, starting from the direct ancestor and proceeding toward the root group, until the specified variable or dimension is found. "For coordinate variables that are not found in the referring group or its ancestors, a further strategy is provided, called lateral search. The lateral search proceeds downwards from the root group width-wise through each level of groups until the sought coordinate is found. This placement of coordinates and lateral search strategy to find them are discouraged. They are allowed mainly for backwards-compatibility with existing datasets, and may be deprecated in future versions of the standard." I didn't understand the justification "Because coordinate variables must share dimensions with the variables that reference them", which I have omitted above. However, it made me realise that the lateral search algorithm may have problems with dimensions. It could find a coordinate variable with a dimension that has the right name e.g. `lat(lat)` but where `lat` isn't the same dimension as in the referring group (i.e. it has a different size) if it's been defined differently somewhere between the root group and the group which contains the coordinate variable. This is dangerous. At least it requires another rule to state that the dimensions must be of the same size as in the referring group. Is the lateral search algorithm intended to work for auxiliary and scalar coordinate variables too? The section on "Application of attributes" would be simpler and more compatible with the conventions if it referred to Appendix A. Maybe I've said that before? It seems to me that global atts mentioned in Appendix A should be allowed as group atts, with some exceptions e.g. `Conventions`, maybe `external_variables`, but why would you made an exception of `title` for example? Perhaps the simplest thing would be to modify Appendix A to show which G (global) atts are not permitted as group atts, and say that other G atts are allowed as group atts. I feel that you don't need to list the variable atts in this section. Sorry to be vague about Appendix I. Yes, I understand and appreciate the intention of it. Please could we talk about that once we've agreed about the text of the main conventions? Best wishes and thanks Jonathan -- You are receiving this because you are subscribed to this thread. Reply to this email directly or view it on GitHub: https://github.com/cf-convention/cf-conventions/issues/144#issuecomment-429236366
