why classname in base id?

[Nicholas Sushkin]

I am trying to write a custom URIResolver, when Apache 2_2_D13 transformer
invokes my customURIResolver.resolve(href, base), the base is of the form

file://dir/javax.xml.transform.stream.StreamSource

What's the purpose of the class name? Isn't base id supposed to be just

file://dir/

so that base + href would be a valid URL?

Thanks,

Nick.