URI length limits versus CAIP-specific length limits - Paradigm Breakage?

[bumblefudge]

In the process of designing a namespace for the evolving Monero ecosystem (which may soon have addresses that are too long for to fit in (or even be compressed into) a 128-char string to be a CAIP-19 address segment!), a few facts have emerged:

1. existing implementations have length limits PER SEGMENT which might be expensive to break
2. there is not explicit consensus on where those limits came from or how to balance scalability and implementability (per-segment limits, limited character sets) against flexibility (works for all namespaces)

A proposal was put forth by @silverpill
A. to make length limits per segment SHOULD instead of MUST with guidance that tradeoffs occur,
and/or
B. to make the WHOLE URI length-limited rather than limit length by segment, e.g. allowing namespaces with shorter CAIP-2s to have longer CAIP-19s.

This makes sense pragmatically but is hard to translate into rigid specifications, particularly since CAIP-2 has a hard length limit and CAIP-19 extends it -- there is not an overarching spec for URIs, just two specific specs that don't require namespace-based parsing, i.e., now any CAIP-19 is parsed the same way, but knowing each namespaces' maximum CAIP-2 would be required to validate each namespaces' CAIP-19s... in summary, a big lift, but more doable as new CAIPs rather than breaking changes to existing ones, I think, if there is demand/interest?

relevant also to #193 -- hard to track implementation conformance as-is, gets harder if breaking changes are made to parsing rules. Perhaps another argument for separate caips that optionally supercede 2 and 19, since some systems might prefer existing uniform parsing and some might require per-namespace parsing, e.g. to support more namespaces

[bumblefudge]

Also note: there have ALSO been issues with the 3 character MINIMUM for CAIP-2 identifiers, which causes some namespace authors discomfort when they describe ecosystems with shorter chainIDs. Does anyone remember why the minimum isn't 1 character?