Clarify designated_period_except definition

[mplsmitch]

---

name: Mitch Vars title: Clarify designated_period_except definition

---

CDS Pull Request

Explain pull request

The current definition of designated_period_except is unclear in that it only covers values named in designated_period. This PR expands the definition to cover all fields in the Time Span. For example, If days_of_week is ['sun'], the Time Span does not apply on Sundays. Additional info in #117

Is this a breaking change

• No, not breaking

Impacted Spec

Which API(s) will this pull request impact?

• Curbs

[schnuerle]

Can your teams take a look at this rewording @jacobmalleau @pierre-bouffort @jiffyclub and make sure that this change does not require anyone to redo their existing code, and that it's not breaking?

[pierre-bouffort]

Hello @schnuerle and thanks for pointing it out. We checked that internally and this is not a breaking change for us so we are good to proceed (from our perspective at least).

[jiffyclub]

Looks good to me.

[jacobmalleau]

It also seems fine to me - this is a welcome addition to the spec.

[jiffyclub]

This does now mean that the designated_period_except field is misnamed since we can use it to indicate exceptions for things other than designated periods, but fixing that up would be a breaking change that maybe we want to do in another release. Potential better names: exception, exception_time_span.

[schnuerle]

This does now mean that the designated_period_except field is misnamed since we can use it to indicate exceptions for things other than designated periods, but fixing that up would be a breaking change that maybe we want to do in another release. Potential better names: exception, exception_time_span.

You may be right here. If we do rename this field then it will have to wait for a 2.0 major release instead of a 1.1.0 patch. Is there some way to clarify this in the field description instead for now?

[LaurentG-AMD]

I feel this changes the way designated_period is used and might make the initial usage hard to achieve in certain cases.

The signs I had in mind when proposing this change are these: which litteraly reads as No Parking Except 9h00-11h00 on Friday from April 1rst to November 30th (I have no idea why parking is only permitted 2 hours during the week but those are real signs I will eventually need to fit in the data model). The current way of coding it would require to make at least 3 Time Spans: "No Parking Sat-Thu" + "No Parking Fri 0-9" + "No Parking Fri 11-24" which is functional when reading the data but make it harder to keep in line with changes when scaled city wide.

Now, there's nothing preventing us to also want to have an exception for snow removal (or whatever reason), where we might want to override it with something else. But in this case, the exception would already be used, so how do we interpret the interaction?

Taking the exemple sign above:

 {
  "months": [4,5,6,7,8,9,10,11],
  "days_of_week": ["fri"],
  "time_of_day_start": "9:00",
  "time_of_day_end": "11:00",
  "designated_period": "Snow removal",
  "designated_period_except":True
}

What happens if we have snow removal on Friday November 15th (of whatever year that happens), is it still a permitted parking or does it become a no_parking? And what about Saturday November 16th where snow operations are still ongoing, can I now park because the sign is voided or is it still a no parking?

I feel if we want to keep both functionalities, they need to use their own exception fields.

[mplsmitch]

@LaurentG-AMD I think for your example above you could do this using multiple policies:

{
  "data": {
		"policies": [{
			"curb_policy_id": "A",
			"published_date": 1552678857362,
			"priority": 1,
			"time_spans": [{
				"months": [4, 5, 6, 7, 8, 9, 10, 11],
				"days_of_week": ["fri"],
				"time_of_day_start": "9:00",
				"time_of_day_end": "11:00",
				"designated_period": "Snow removal",
				"designated_period_except": true
			}],
			"rules": [{
				"activity": "parking"
			}]
		}, {
			"curb_policy_id": "B",
			"published_date": 1552678857362,
			"priority": 2,
			"rules": [{
				"activity": "no parking"
			}]
		}]
	}
}

Policy A allows parking 9h00-11h00 on Fridays, April 1st to November 30th, but not during snow removal. Policy B prohibits parking at all times. Since Policy A has a lower priority it would take precedence over B during the Friday 9-11 timespan. Does this seem like it would work?

Also, are you still interested in exceptions to user classes? Maybe we could add it to this PR.