Query string values that mean "not set yet".

[SiBell]

Example

Let's say I want to get a list of all my sensors:

GET /sensors

If I want to get all the sensors in a given deployment then I could use:

GET /sensors?inDeployment=public-weather-stations

Now what if I want to get all the sensors that are not in a deployment yet?

Possible solutions:

1. GET /sensors?inDeployment=false

Downside: You'll have to ban deployments called 'false'. The same would apply if you used null instead of false.

2. GET /sensors?inDeployment=

Downside: This is ambiguous as to whether it means a) give me all sensors whatever the deployment, or b) gives me sensors not in a deployment.

3. GET /sensors?assignedToDeployment=false

Downside: You need to document another query string parameter. And probably forbid the presence of inDeployment when assignedToDeployment=false.

[lukeshope]

Could we adopt the same approach proposed for greater than/less than cases?

Something along the lines of inDeployment__isNull=true or inDeployment[isNull]=true?

[SiBell]

Works for me.

I'd planned not to include any Null values in my API response, i.e. this:

{
  "id": "sensor-1",
  "name": "sensor 1"
}

Rather than this:

{
  "id": "sensor-1",
  "name": "sensor 1",
  "inDeployment": null
}

Assuming it's fine to omit null properties, and doesn't break any rules of the standards we're sticking to, then perhaps inDeployment__isDefined=false is better?

[lukeshope]

Happy to go with isDefined as a the condition, I agree about not including nulls in these cases. Should we come up with a list of all the conditions we think we might need to use as query parameters, and the types they're applicable to, as in

• isDefined can be used for IRI references
• gte, lte, gt, lt for numeric values
• contains, overlaps, withinDistance or similar for spatial conditions
• straight forward equals for booleans, strings, etc.
• wildcard or regex matches for strings?

[SiBell]

Yep good plan. Pop them in a table and whack it in the standards draft, e.g:

conditional	properties types applicable to	description	example
gte	numbers, date strings	Filter resources by property values greater than or equal to that specified	startdate__gte=2019-05-24

What me to make a first stab at this?

[lukeshope]

Closing this as discussion of the same matter has now moved to #18.