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Ticket Resolution Summary Owner Reporter
#48 fixed Minor typo in equivalent_reflectivity_factor definition apamment Greg Rappa
Description

The word reflectivity is spelled incorrectly as "relectivity".

This typo appears in both files: cf-standard-name-table.html and cf-standard-name-table.xml

#76 fixed More than one name in Conventions attribute davidhassell Dave.Allured
Description

Introduction

It is proposed to support the listing of more than one convention name in the Conventions global attribute. As of CF-1.6, only the CF identification by itself is allowed. The option of a list has been in Unidata's recommendations for a long time; see references. There was some community support for this in the recent mailing list discussion.

Process

I would like to present this in two parts. This trac ticket is part 1, which proposes to adopt verbatim, the Unidata language for listing more than one convention name. The original Unidata recommendation allows the list of names to be separated by either spaces or commas.

Part 2, which I plan to file as a separate ticket, would propose more detailed parsing rules and would probably replace the syntax description of part 1. The main objectives of part 2 would be to accommodate both unambiguous machine parsing, and flexibility in allowable characters in convention names.

Why two tickets? I think that part 1 has a better chance of approval. It accomplishes the most important objective of multiple conventions in a workable way. If part 2 succeeds, it can replace part 1, sooner or later.

The mailing list discussion beginning December 2011 should be considered part of the record for this proposal.

Text of proposed changes

Two new paragraphs are to be added at the end of the current section 2.6.1, Identification of Conventions:

It is possible for a netCDF file to adhere to more than one set of conventions, even when there is no inheritance relationship among the conventions. In this case, the value of the Conventions attribute may be a single text string containing a list of the convention names separated by blank space (recommended) or commas (if a convention name contains blanks). This is the Unidata recommended syntax from NetCDF Users Guide, Appendix B.

When CF is listed with other conventions, this asserts the same full compliance with CF requirements and interpretations as if CF was the sole convention. It is the responsibility of the data-writer to ensure that all common metadata is used with consistent meaning between conventions.

In the conformance document, add a new second line under 2.6.1 Identification of Conventions:

  • The Conventions attribute may be a single text string containing a list of convention names separated by blank space or commas, one of which shall be the full CF string as described above.

References

Current language of section 2.6.1, Identification of Conventions (CF-1.6)

NetCDF Users Guide, Appendix B, Attribute Conventions

List of registered conventions, NetCDF website

Ticket #27, Use namespace tags to include other conventions, 2008
(Previous proposal and discussion of Conventions attribute, not yet adopted)

#148 fixed New cell_methods: mabs/mibs/mebs davidhassell zender
Description

1. Title

Add absolute value statistics to cell methods

2. Moderator

David Hassell

3. Requirement

The statistics mabs/mibs/mebs stand for "Maximum absolute value", "Minimum absolute value", and "Mean absolute value", respectively. They are similar to max/min/mean statistics, and they can be useful in characterizing data when one wants positive-definite metrics. mebs (unlike mean) does not allow positive and negative values to compensate eachother. Unlike rms, mebs not does weight outliers quadratically. NCO implements mabs/mibs/mebs as fundamental statistics (like max/min/mean), and annotates the cell_methods attribute of variables reduced by these statistics with the strings "maximum_absolute_value", "minimum_absolute_value", "mean_absolute_value".

4. Initial Statement of Technical Proposal

This recommendation could be implemented in CF by inserting the following lines into Table E.1. Cell Methods

http://cfconventions.org/Data/cf-conventions/cf-conventions-1.7/build/cf-conventions.html#appendix-cell-methods

cell_methods:		Units:	Description:
maximum_absolute_value	u	Maximum absolute value
minimum_absolute_value	u	Minimum absolute value
mean_absolute_value	u	Mean absolute value

5. Benefits

This would improve the CF-compliance of fields processed by absolute-value statistics.

6. Status Quo

There is no standard CF terminology to describe absolute-value statistics so fields analyzed with these methods may have missing, erroneous, or non-standard cell_methods for this stage of processing. Unless the statistics were computed with NCO which has implemented the proposed cell_methods since February, 2015.

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