Example 17 "Different type of identifiers" contains not-recommended value

`dc:identifier` value SHOULD be formatted using a Uniform Resource Name

but example 17 includes:

```xml
<dc:identifier>
   https://en.wikipedia.org/wiki/Braille
</dc:identifier>
```

I'm not sure if this is intended?

Should the content model be loosened to URL? or at least describe that the example shows a non-recommended value?