definition of valid time is unclear

[ricardogsilva]

Section 9.2.2 of OACS Part 1 specifies validTime as being:

The validity period of the system’s description.

Later in the GeoJSON format description, section 19.1.5 System Representation, Table 40, this property is mapped to properties/validTime and described as:

Value SHALL be a JSON array with min/max bounds encoded as a ISO8601 date/time string.

Based on this I would expect that validTime would always be a JSON array with two datetimes.

However, I'm seeing a server respond with something like this:

"validTime": ["2026-01-01T00:00:00Z", ".."]

I don't think the string ".." is a valid ISO8601 datetime representation. Nevertheless, using ".." as a way to represent an open temporal bound is a familiar idiom from the OGC API - Features spec. It also seems very reasonable that the OACS standard would allow specifying an open-ended bound for validTime. As such I am assuming this server's response payload is valid. Unfortunately, I've not been able to confirm this in the actual OACS standard document nor its accompanying schema.

I think the text of the OACS document ought to mention it explicitly.

I went looking for the schema of this validTime property and could not find it anywhere. The schemas published in the schemas.opengis.net repository define it like:

            "validTime": {
              "description": "Time period during which the system description is valid.",
              "$ref": "../common/commonDefs.json#/$defs/TimePeriod"
            },

and the referenced JSON:

    "TimePeriod": {
      "$ref": "../../../../../common/timePeriod.json"
    },

This last $ref seemingly points to nowhere though. I can't find it anywhere. I tried doing a text based search for TimePeriod and all I could find are references to it, but no actual definition. I also searched directly in this repo and could not find the definition either. Am I searching it wrong?

Would it be safe to assume that ".." is a standard way to define an open-ended temporal bound in OACS?