Units

[Michael O'Brien]

I'd like to propose that the URL in the Unit pragma be optional.

The current usage is:

use unit UnitName StringLiteral

where the string literal is usually a URL from which to locate and load 
the unit.

I can imagine a use case where the unit source itself may not know where 
the unit will be located for download.
This may vary from hosting site to hosting site and may indeed by dynamic.

The UnitName can be a Path, so constructs like:

use unit com.mbedthis.js

can provide a search strategy to find the unit by following a site 
dependent mechanism to locate "com.mbedthis.js".
This may be in directories like Java dictates. E.g. com/mbedthis/js.EXT

An alternative is just to ignore the URL, but it seems that putting a 
file system specific storage URL in the code is not the right place.
Unless this is considered just as a unique string like Namespace URIs. 
What was then intent here?

Lastly a question: are "use unit" pragmas runtime or compile time 
directives?

Michael O'Brien