Reachable Documents

On a document being accessible by a User. -- ThinkingOutLoud.DonaldNoyes.20090302.20110104

This is a class of documents which have the characteristic of being reachable.

But for unreachable documents, often the result is an error or an exception.

In Html documents reference to document and/or a resource is made using the [ <a ] anchor element. How this is handled is dependent on what remains within the anchor element. Guidance on what to do in this case is defined in the W3C document as follows:

12.2.4 Unavailable and unidentifiable resources

A reference to an unavailable or unidentifiable resource is an error. Although user agents may vary in how they handle such an error, we recommend the following behavior:
- If a user agent cannot locate a linked resource, it should alert the user.
- If a user agent cannot identify the type of a linked resource, it should still attempt to process it. It should alert the user and may allow the user to intervene and identify the document type.

An example of one kind of handling is found when in a Google search a document is reachable, even if the site at which the document is stored is temporarily or immediately unavailable, using the "cached" feature found in the search results.

A user might handle this by creating a similar feature by creating a "CachedCopy?" or an alternate linking mechanixm to a resource made reachable via another URI.

What ReachableDocuments does not mean is that the document's first and subsequent URIs are "reachable", particularly if they are site related or have not been provisioned as cached copies by the user. (There exists means to "rip" websites by following subsequent links to a specified level of linkage.)

A ReachableDocument? therefore can be made a "local document" by the creation of a controlled and certain document within the "user's reach".

A second kind of the "ReachableDocuments" could be those that are "provisionally" reachable, in that the user provides verification or validation of a right to acquire the document. This could be by being a verified member of document users of the providing resource, via login and password verification, or by the provision of certification or by PurchaseTokens? or OpenCommunityCredits?.

The means of indicating a reachable document could be up to the user, via a mechanism that could have a SpecialLink? markup such that two or more references are supplied as hyperlinks, the first being the "normal", and the second being the "alternate" (another site, or a CachedCopy?).

Here are examples of such references:

The first here references a document that is purposely unavailable and will yield a 404. The action of the user is to back arrow and then click on the next [20090327] which exists to point to a historical or versioned cached copy, or to an alternate site.

 <html>
 <head>
  <title>ReachableLink??</title>
 </head>
 <body>
  <h2>Reachable Links</h2>

  The provision of links in a manner that makes this
  <a href = http://donaldr.noyes.com/ReachableLinks.htm>
   <em>NamedLink??</em></a>
   <sup>
     <a href = http://donaldr.noyes.com/ReachableLinks.htm>[20090327]</a>
   </sup>
 </body>
 </html>

The second here references a document that is available and will yield a page. It is necessary to back arrow and then click on the bracketed [20090327] to reach the alternate. The example uses a SpecialLinkingPresentationFormat developed for handling this kind of artifact.

In this wiki, this provision is provided when the link is to a page within the wiki. It it exists, the link only is shown, if not, a ? follows the would be link, as it does for this WouldBeLink? The ? is a visible link to provisions to create pages. (aka WantedPages)

 <html>
 <head>
 <title>ReachableLink?</title>
 </head>
 <body>
 <h2>Reachable Links</h2>

 The provision of links in a manner that makes them
 <a href = http://donaldr.noyes.com/ReachableLinks.htm>
 <em>Reachable</em></a>
 <a href = http://c2.com/cgi/wiki?ReachableLinks>
 [23457]</a>
 </body></html>

The alternate might also be used to explain why a document is not available and provide the means for provision of the document if it is one controlled by a verification or other process.

What would make this a one click process is a browser feature similar to the "alt =" feature in "<img" provided for in the "<a href = " followed by the "alt =" with the second alternate being a certain reachable reference. As far as I know, it is not available in any browsers I have used to date.

If a collection of pages exists, for example those collected about a given topic, in a dedicated, known and reachable directory, the existence or non-existence of a page with the name of the clicked upon word is an easy programming task. One of the advantages of this approach is that it will allow any space-delimited strings of characters which include only filename valid characters, to be links.

Nice. I have been using a personal version of this for years, but this would be a very handy addition to hyperlinks and WebPages? in general. What I have done, is to replace Notepad with Metapad (which allows for hotlinks), and then when I create text notes for myself, I often keep a local copy of a linked page using file:/// (and %20 for spaces) as an alternate. --Seattle1 [Example: file:///C:\Documents%20and%20Settings\you\My%20Documents\stuff\ideas\availability.txt]

Metapad can be found at: http://liquidninja.com/metapad/