URL Scheme Decision

[egekorkan]

We have or had URL Scheme discussions for MQTT, OPC UA, BACnet and Modbus. This is a parent issue that will summarize the discussions in various places so that we can make a point and get further feedback from TAG.

Related issues/discussions:

• MQTT: MQTT URI Design wot-binding-templates#292
• OPC UA: opcua: nsu in nodeId (fixing #1334) eclipse-thingweb/node-wot#1335
• BACnet: BACnet URI Design wot-binding-templates#387
• Modbus: feat(modbus): move addres and quantity to URL components wot-binding-templates#183

The core issue stems from nudging different protocols to use URIs to reflect a resource. Not all protocols can do that as the URI standard has reserved characters like # and we use JSON, which constrains strings to have " on both ends, requiring escaping if the protocol in question also uses " for names.

The decision so far is to make sure that all protocols' resources can be used in the href field, which is a IRI (https://www.w3.org/TR/2012/REC-xmlschema11-2-20120405/#anyURI). So far we have been requiring protocols to slighthly adapt when used in the context of WoT and the TD TF is still willing to do that. If you have opinions about the general requirements, please comment here. If you have opinions on the specific protocols, please use the issues linked above.