Maps4HTML
<input type="location" min="..." max="..." units="tilematrix">
The question arises as to how to set and how to interpret the min/max attributes on location inputs, because there are many coordinate systems (levels) in a TCRS, and the level is not necessarily spelled out at run time, as it changes as the client zooms in and out, where as the bounds of the axis should remain constant regardless of zoom level.
I think it will be necessary to allow any in the extent to specify a and use that value to infer that the min/max values on refer to that zoom level.
What do you think of that idea?
An alternative might be to specify min/max in terms of pcrs or gcrs.
I believe the first idea is implemented in this prototype service, for example:
<mapml>
<head>
<title>Canada Base Map - Transportation (CBMT)</title>
<meta http-equiv="Content-Type" content="text/mapml;projection=CBMTILE"/>
<meta charset="utf-8"/>
<link rel="license" href="https://www.nrcan.gc.ca/earth-sciences/geography/topographic-information/free-data-geogratis/licence/17285" title="Canada Base Map © Natural Resources Canada"/>
<link rel="zoomin" href="/mapml/en/cbmtile/cbmt/?z=18" type="text/mapml"/>
</head>
<body>
<extent units="CBMTILE">
<input name="z" type="zoom" value="17" min="0" max="17"/>
<input name="y" type="location" units="tilematrix" axis="row" min="29750" max="34475"/>
<input name="x" type="location" units="tilematrix" axis="column" min="26484" max="32463"/>
<link rel="tile" tref="https://geoappext.nrcan.gc.ca/arcgis/rest/services/BaseMaps/CBMT3978/MapServer/tile/{z}/{y}/{x}?m4h=t"/>
</extent>
</body>
</mapml>