| YEP: | 311 |
|---|---|
| Title: | has-mapping |
| Authors: | Blaise Thompson |
| Status: | draft |
| Tags: | trait |
| Post-History: | 2020-10-29 |
This YEP defines the concept of "mapping" arrays. These arrays add additional "context" to the channel arrays defined by is-sensor (YEP-302). For example, a mapping might describe which wavelength of light falls upon each pixel of a spectrometer array detector.
Certain sensors contain important information beyond their raw values. Consider an array-sensor within an optical spectrometer. Such an array detector could be implemented according to the is-sensor trait (YEP-302), with a channel for the measured light intensity at each pixel. To use this information, however, clients must also know the relationship between pixel index and light wavelength: the "mapping" of the array detector. This YEP defines a trait which allows daemons to expose mapping information over a consistent interface.
This trait requires is-sensor (YEP-302).
This trait implements mappings as a collection of arrays completely separate from channels.
The principle feature of this trait is the new message get_mappings.
response: {"type": "map", "values": {"type": "array", "items": "string"}}
Keys being channel names. Values array of keys from get_mappings. Can be many mappings per channel, or no mappings for a given channel (empty array).
Mappings must have the same dimensionality as their associated channel. Do not need to be the same size. They must broadcast into their associated channel.
response: int
Mapping ID. This integer increments every time the mapping is updated. Clients can safely check this id to verify that their cached mappings are correct, if desired.
response: {"type": "map", "values": ["null", "string"]}
Must return units for every mapping. Units can be null.
response: {"type": "map", "values": ["double", "ndarray", "int"]}
Keys used in get_channel_mappings
At one point in yaq development, mappings were included simply as additional channels. While elegantly simple, this idea proved insufficient.
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