What is a Linkable Reference?

The word "creation" includes both works and manisfestations.

In the ideal world, there is one digital surrogate for each linkable work. The digital surrogate provides all the information needed to make a work linkable. In the real world, there will be one surrogate for each item in an archive that we process.

We distinguish between the following:

• A reference is abstract; it is a creation. It always has a URI. It need not have a location on the net.
• An item (in the IFLA sense) in a repository or anywhere on the net is something from which we can extract bibliographic data. It has a URL.

What properties of a digital object [sic] make it linkable?

-  It is online, to be more specific, on the internet.

-  It is addressable, more specifically, it has an URL.

-  Linkable != Referenceable

   Lots of referenced objects are not linkable because they
   cannot be found, or because they are incorporeal, or other
   reasons.  
   I can reference a 1980 article in
   CACM, but if I cannot find a copy of it on the web, it is
   not linkable (ACM has online papers only since 1985 or 1995).

-  Linkable == findable, at present

   Well, actually, nameable and findable.  All documents have a
   URI, even if it is just a hash of its bibliographic data.  If the
   URI happens to be a URL, or resolves to 1 or more URLs, then 
   it is linkable because you can perform GET and HEAD on it, as
   long as the URL is valid.  To be findable on the net by google
   search, for example, indexing on it is permitted, it must not be
   a hidden directory, and robot rules do permit access.

- Linkable == Findable, but Findable != playable

   Not an issue.  It is irrelevant whether your browser can
   render the object.

- Linkable != having a permanent name

   One could say that linkability is an evanescent property.  An
   object is linkable if it can be accessed today.  But if it 
   cannot be accessed tomorrow (even due to a
   server error, say), then the object becomes unlinkable.

   But we decided
   on 3/13 that while the linkability property is not immutable, it
   is relatively stable for some definition of "relatively stable".  
   We are not going to worry about 404 errors or other very transient
   conditions.

   We did not discuss the question of whether today's weather in 
   Ithaca, which is digitally available and has a permanent URL, is 
   linkable.  But we did agree that if a reference contains a 
   temporal element that is relative
   ("today's weather, Carl's last paper) then it is 
   *not* linkable even if it does have a URL.  

- Linkable != "has metadata"

   Some objects may not have metadata included in them, but they are
   still linkable, because they have a known URI.

   I included this item only because so often the need for metadata is
   justified by the need for resource discovery.  Resource discovery
   is very closely related to Linkability.  

   We all agree that access rights and/or charges are not part of 
   Linkability.  They are orthogonal considerations to linkability.