Re: [xml-dev] Style, Substance and Typing in Schemas

[John Cowan <cowan@mercury.ccil.org>]

Andrew Welch scripsit:

> > Since in Java,  URI is not a subclass of String,  it make sense that anyURI in XSD should not be a subclass of String.
> 
> That's probably (see above) because you don't want URI inheriting all
> the methods in String.

For a variety of reasons, String can have no subclasses in Java.  The
most important of these is that Strings are immutable (and therefore
safely shareable between threads), and for an immutable class to have
potentially mutable subclasses is asking for trouble.  But of course
this has nothing to do with XSD datatypes.

> Yeah that seems reasonable... what I don't understand is why '' (empty
> quotes) is a legal xs:string and xs:anyURI, when is that useful?

A string can be of any length, including zero.

An empty string when interpreted as a URI is basically a reference
to the current base URI.

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