Summary section 4.3 should must not mandate client server roles of specific blocks

[mlagally]

Text and picture in section 4.3 constrains client and server roles on the device / cloud blocks. This is only informative, however it contradicts normative sections which don't impose client or server functionality on individual blocks (devices, servers, edge devices).

The figure and text needs to be updated to make this very clear.

[k-toumura]

Currently, we use the word 'server' in following four meanings:

1. An entity which provide a (abstracted) Thing
   • In Terminology section: 'WoT server: An entity that exposes a network interface consistent with a WoT Thing Description. …'
2. A passive reactive component in communication
   • In 4.2.1: '… one device … has a server role that can accept a request from the other devices …'
   • Issue Don't enforce server paradigm on devices #146: 'use cases … don't require adopting a server model in the thing'
3. A computer, (virtual) machine, process. program, etc.
   • In 4.2.6: 'a model of a device … that resides on a cloud server …'
4. A entity which is in the Internet
   • @chachamimm mentioned in issue Describe Server and Client at the section "6.2 WoT Architecture" #188: 'Basically in Internet Server is the global network, and Client is the local network.'

In use case section, we use the term 'server' to refer to 1, I think.
But we can't use the term 'WoT server' in use case section to clarify the meaning, because it is a WoT-specific terminology.
So I think it is helpful for define 'server'(and 'client') as 1 in the beginning of 4.2 Common Patterns.
Or, we can use 'Device/Application', 'Provider/User' or some other terms which do not imply the meaning of 2,3, and 4 of above for describe the entity in Use Case section.

One of the drawback is we can't express difficulty of NAT and firewall traversal problem on Use Case section, because the problem is caused by a deployment pattern of active/passive component.(2 of above listing).