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Consider the humble key / value pair; both beautiful and powerful in its simplicity. It has a weakness however. The key is limited in how much shared meaning it can effectively communicate without compromising the brevity that is another feature of the key / value approach. The solution was to create a controlled vocabulary of "keys" that would allow for the detailed description of the data point of interest while being kept separate from its usage.
AgGateway’s SPADE project implemented a RESTful API to provide a machinereadable vocabulary of CI definitions; its Standards & Guidelines Committee created an adhoc group to manage the vocabulary.
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