> On May 13, 2018, at 11:42 PM, Neil Van Dyke <n...@neilvandyke.org> wrote:
> John, thank you for your past&present work on the SXML stuff. Two comments:
>> enforcing the “file://“ prefix.
> Sounds like the following doesn't matter in this case, but another way to 
> support both a given URL or given filename is to resolve the given value as a 
> possibly relative URL, against a base URL that's a "file:" scheme URL for the 
> current working directory.

I’m not sure what you’re proposing here; the (now current) code simply strips 
off the “file://“ prefix and uses (IIRC) `file-exists?`. IIUC, that would 
support relative file urls. Is that what you’re proposing, or is that something 

>> I’ve made a change that appears to allow the use of “file://“ URIs with 
>> sxml:document,
> As soon as tools get into accessing resources via URLs from the XML (which I 
> don't think is what you're doing, but it might be the next step for someone), 
> it should be documented that there's a need for access control.
> For example, imagine an application in which user-supplied XML specifies a 
> (purported) schema with a "file:" or "http:" URL to some resource to which 
> user doesn't have access, but the XML processor does.  If the application (or 
> XML library it uses) attempts to access that URL too trustingly, then the 
> user maybe be able to cause some privileged side-effect (e.g., manipulate a 
> database, or control an IoT device), or learn some or all of the content at a 
> URL (via, e.g., a too-detailed error message), or learn something about the 
> system (e.g., something more about its location/operator/implementation, if 
> it makes an outgoing request to a server user can monitor).

I’ll be honest: I don’t think that the current system can resolve any http 
references (in fact, I see code that handles that which is commented out), and 
I also think that it’s not designed to resolve remote schemas, but I’d love to 
have a more detailed example, if you have one handy. 

Honestly, I don’t really think that this package should have anything to do 
with resolving URIs; I’m tempted to redesign it in such a way that it accepts 
as an argument a function used to deal with the whole URI side of the world. 
Units, anyone?


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