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#105: Scalar Coordinates -----------------------------+---------------------------------------------- Reporter: markh | Owner: [email protected] Type: enhancement | Status: new Priority: medium | Milestone: Component: cf-conventions | Version: Resolution: | Keywords: -----------------------------+---------------------------------------------- Comment (by markh): Replying to [comment:1 stevehankin]: Useful questions Steve, thank you A point of view on these from me: 1. what is the semantic difference (not the syntactic difference) between a coordinate variable and an auxiliary coordinate variable? * an Auxiliary Coordinate variable describes dimensions of a data variable, it is not definitive; * a Coordinate Variable provides a definitive, ordered, reversible definition of one dimension of a data variable. 1. through what syntax does the semantic distinction in question 1 get represented when the coordinate variables are of length 1? * If there is a relevant dimension of size 1 defined in the file, then the facilities exist to make the distinction. * However, scalar coordinate variables do not vary with any data dimensions * as such they are not Coordinate variables, they are more like Auxiliary Coordinates which describe zero data dimensions. * Because they are scalars it is a very easy step to promote a scalar to a coordinate variable, a vector, by adding a dimension * thus they may be treated as functionally equivalent by the data consumer * however, this is an extra step, taken by data consumers, adding information to the data set * This distinction recognises that Scalar Coordinates are semantically less rich than other vector coordinates. 1. does CF regard the mathematical distinction between a scalar and vector of length 1 as significant? * I think it does, in it's current use in various places in the conventions document and the community; * a scalar is a different thing with different properties from a size one vector: * I don't think this is hair splitting, I think it is useful and a facet that will be generally recognised by data consumers and creators. -- Ticket URL: <https://cf-pcmdi.llnl.gov/trac/ticket/105#comment:4> 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.
