Thanks for taking the time to reply with such a well thought out and thought-provoking response.

Firstly, I want to say that as someone who is an architecture/design enthusiast, I totally agree with the sentiment of your message. Good design is all about exploring options and identifying nuances in the domains, and using heuristics to find the most suitable model.

We could stretch the library example to consider that a person physically in the library is actually reserving the book. They have a limited amount of time to either check-out the book or decide they don’t want it and put it back. But no metaphor is perfect.

I like your heuristic. If the context isn’t the source of truth, then we should make this explicit in the design. Perhaps as part of checking out the item, it is the recipients to job to confirm they actually were able to check it out (another kind reservation, although different semantics).

I feel also that whenever the inventory is physical items, there is always a chance the system can become out of sync with reality, unless the IoT devices are fully instrumented and the system knows/can detect when they are broken.

In summary, I agree with your summary. There are a lot of factors that impact design, and for me there is a lot of value in having these conversations.

Thank you