range in data_keys

[untzag]

There might be general interest in adding "limit" or "range" information to data_keys in the event descriptor [1]. The primary goal is to have more intelligent defaults for live-plots and autogenerated post-processing.

Ophyd v1 already does this [2] with their own special keys lower_ctrl_limit and upper_ctrl_limit. data_keys object in the schema supports arbitrary additional properties (items) I guess this is a JSON schema default.

See @ddkohler's issue against YEPS [3]. The Wright Group has a long-standing concept of data being "signed". Seems like this behavior could be captured by special cases of range for their purposes.

WrightTools signed	Descriptor range
False	(-inf, +inf)
True	(0, +inf)

We could have multiple range types perhaps. Display range, alarm range, warning range, control range. What do existing systems do?

interface	properties
Ophyd.v1	lower_ctrl_limit upper_ctrl_limit
PyTango	get_max_value get_min_value is_min_warning is_max_warning is_min_alarm is_max_alarm
yaq	get_limits

[1] https://github.com/bluesky/event-model/blob/master/event_model/schemas/event_descriptor.json
[2] https://github.com/bluesky/ophyd/blob/master/ophyd/signal.py#L1469-L1470
[3] yaq-project/yeps#15

[untzag]

I think the concept of display, warning, alarm seem fairly well conserved.

[coretl]

When trying to expose in GraphQL in such a way that it worked for both EPICS protocols (Channel Access and PVAccess) I came up with this:
https://github.com/dls-controls/coniql/blob/master/src/coniql/schema.gql#L179-L221

[coretl]

Channel Access fills them in like:
https://github.com/dls-controls/coniql/blob/master/src/coniql/caplugin.py#L98-L113

[coretl]

PVAccess like this:
https://github.com/dls-controls/coniql/blob/master/src/coniql/pvaplugin.py#L125-L137

[coretl]

Ophyd.v2 can do the same

[untzag]

Thanks as always for your careful response @coretl!

[danielballan]

One possibility: standardize on a key like limits or range and then, within that have open-ended sub-keys, as in:

{
    ...,
    "limits": {
        "warning": [-5, 5],
       "alarm": [-6, 6],
    },
}