Explain issue with URI query parameters

[mkovatsc]

The URI query is just a piece of string after the question mark. There is no global specification how it should be parsed etc.

HTML defined the usage of & , which is supported by CoAP, but implementations handle it differently, for instance, when a query parameter occurs multiple times.

[akeranen]

For GET query filter should often rather use FETCH. In general better to use payload than query parameters. But OTOH bookmarking better with query params.