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URI types and functionality (Re: Do sheep dream of electricURL

• To: Rick Jelliffe <ricko@a...>, danny666@v..., xml-dev@l...
• Subject: URI types and functionality (Re: Do sheep dream of electricURLs?)
• From: "Emmanuil Batsis (Manos)" <mbatsis@h...>
• Date: Sat, 17 Aug 2002 19:36:17 +0300
• References: <EBEPLGMHCDOJJJPCFHEFAEPBHHAA.danny666@v...> <049801c245eb$21f7e340$4bc8a8c0@A...>
• User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.1b) Gecko/20020721

Rick Jelliffe wrote:

>My golden retriever Pip does not believe that there can be resources
>that cannot be retrieved. He has done substantial empicial work to
>prove this, and I believe he would respond to an invitation to join the TAG
>enthusiastically, having an enormous understanding of REST.
>

I bet.

>Resources for retrieval can be anonymous, or pointed to (by him 
>or me) or named (he only understands the scheme "fetch:" however.)
>

This suggests that your golden retreiver needs nothing more besides the 
location (where the resource can be found) and  (perhaps) the fetch: 
scheme (;-)  thus no names are requiered for the function of retreival; 
the location is the name because it resolves into one physical unit thus 
is unique and proper as a name.

When beyond the stage of retreival being the only function, the location 
is just as good as a name since it resolves not to a space but the 
actual resource thus is unique. The choices here are either:

* consider the location to be valid for both functions (naming and 
resolution) and be prepeared for failing attampts of retreival (404s in 
our case) or,

* use the fetch scheme to distinguish between the resources that can be 
retreived.

This shows us that all schemes designed to locate something, are as good 
for names as they are for locations, when those resolve not to a space 
for resources but to an actual resource. Starting to map all this to 
URIs, one may concude that an unknown URL can safelly be used as a name 
since it's a URI, but must point to a resource (and not wait for a 
default resource in that space) to be used as a locator. If it does it's 
valid even if that resource does not really exist; everyone can handle 
404s, besides that's what 404s where designed for.

So everything is safe if you do not use schemes for retreival if they 
where not designed for it and,  freely use schemes designed to locate 
resources as both names and locators if you are dealing with a 
retreivable resource.

Back to your dog now, he has no problem with the fetch: scheme being the 
actual command since he only understands physically accesible resources, 
whether he is able to retreive them or not. We on the other hand, 
distinguish between the schemes and the commands that trigger the 
functions these schemes are capable of, since  schemes should be used to 
denote the avaliable functionality one can use the URI for.

Then again, Pip does not need to worry about that and I think he is in a 
better position than I am.

>After playing hide-and-seek recently, he has become convinced of
>my bilocationism:
>

Ok I'll try this one too. So, URL, able of being both a name and a 
locator, may be used as a local name for something that is not actually 
where it locates it, if the resource space responds by fetching a remote 
resource for us.

I wish Pip could share his lights here.

Cheers,

Manos

• References:
  • Do sheep dream of electric URLs?
    • From: "Danny Ayers" <danny666@v...>
  • Re: Do sheep dream of electric URLs?
    • From: "Rick Jelliffe" <ricko@a...>

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