Looking at the demo given in Solid World, I noticed that some of the properties are being declared with urn:tmp, which is not a url. I was surprised to see that because I thought every property had to be a url.

I am wondering if that makes sense in this application because the data is auto-generated from an external API and the data is not stored in the Solid POD, so the data in the returned document is "temporary" in that sense. Or is that just because this package is only for demonstration purposes, and this pattern should not be used in production.

Doing a quick search online the only documentation I could find about this pattern is in this tutorial, and it mentions that it shouldn't be used in production.

One of the main problems I face making apps is to define which data structure to use, and as I understand it every property should be declared with a vocabulary that is accessible online as documentation. If I ever need a custom property that is not declared in an existing vocabulary, is it ok to use this kind of thing? For example using <my-custom-vocabulary:customprop> instead of <https://my-custom-vocabulary.com/customprop> (having to host an ontology on https://my-custom-vocabulary.com).

I suppose it is possible technically, but I wonder if it is discouraged for production and considered bad practice.