People have generally discovered on today’s Web, that even if they just right-click on any item and choose “Copy Link Location” as offered by their browser, they get a URL of such a sort, that next, when they embed that URL into a posting or into a site of their own, within some time the real URL changes and the one they copied / dragged no longer works.

This is why URLs / Hyperlinks have long been reinvented in the form of so-called “Permalinks”.

All my postings and pages offer Permalinks to the reader. On a blog posting, right-clicking or tap-holding on the Title, will offer to Copy the Permalink. For pages, right-clicking or tap-holding on the entry In the Sidebar or Header of my Main Page, will do same.

(Edit 01/14/2017 : This blog is generated by a collection of PHP server-scripts – aka CGI scripts – and uses HTML-5. This is a form of HTML which advises content-providers against using the old formatting tags for Italic, Underscore and Bold, instead suggesting Strong or Emphasized.

Because this blogging engine observes HTML-5 100%, the pieces of text which seem underlined, are generally URLs which the reader can click on.

When we use a Desktop or Laptop, our browser allows us to hover over these hyperlinks with our mouse, and displays a bubble which describes what sort of link it is.

But, when we use a tablet or a smart-phone to read a Web-page, there is no hover-support, because we usually do not use a Bluetooth Mouse. In such a case, some readers might have overlooked the fact, that each underlined segment of text is in fact a link, unless they were to tap on that link.

Generally, readers do not tap on random places within pages of text, unless they already know that the pages contain hyperlinks.)

(Edit 06/05/2017 : )

I suppose that there is another piece of information which I can offer, which actually describes permalinks.

According to more-old-fashioned thinking in HTML and Web-design, a site is organized into folders, which contain either HTML Files or CGI-Scripts. URLs would have put the folder-names into their path, leading up to the file-name of either the HTML File or the CGI-Script.

According to that rule, the following URL should have a nonsensical meaning:

http://dirkmittler.homeip.net/blog/archives/3051

According to ages-old wisdom, my site has as its root folder, a folder named ‘blog’, and it supposedly has a sub-folder to that one, named ‘archives’, and another sub-folder to that one named ‘3051’. Further, it would seem that our URL does not specify what file, or what type of file to open, either belonging to the folder ‘archives’ or belonging to the folder ‘3051’.

This way of representing URLs is used often today, by sites that actually manage a large collection of pages. The reason these URLs work, is the fact that before executing server-side CGI-Scripts, sophisticated Web-servers apply “Rewrite Rules”. These Rewrite Rules are specific to one site – such as to my blog – and consist of ‘Regular Expressions’, by which the server recognizes patterns in the URL, and by which it replaces the pattern systematically with another pattern. So the above URL gets rewritten by my Web-server, to do exactly as the following URL does, without your browser getting to see that this happens:

http://dirkmittler.homeip.net/blog/?p=3051

What the browser would be requesting with the above URL, is that the default CGI-Script for the root folder be executed on the server, using the GET-Method, and setting the variable ‘p’ to the value ‘3051’.

The latter types of (more old-fashioned) URLs generally also work, with two main drawbacks:

1. They are humanly undecipherable,
2. Web-Masters are likely to change them. If they were to change, these would no longer qualify as permalinks.

‘WordPress’ offers its bloggers a selection of types of permalinks, including:

http://dirkmittler.homeip.net/blog/2017/06/Linear-Predictive-Coding/

Again, there is no file in any folder ‘…/2017/06/’ by the name ‘Linear-Predictive-Coding’. But, subscribers to newspapers and some blogs would benefit from this rewrite rule, because if they were Copying and Pasting numerous URLs, they would be able to tell at a glance, which one was which. This could be more useful to some readers, than just to see that one of them was ‘…/3051′. And so this specific feature, of ‘A Descriptive URL’, has also become synonymous in some people’s minds, with the concept of ‘Permalinks’.

If the reader needs to know in greater detail how this works, This is an external explanation, specific to WordPress. It highlights the fact that PHP-Scripts can access what the original URL was, using the environment (array) variable 'REQUEST_URI', which indexes the array \$_SERVER .

I suppose I should add another detail. When a ‘WordPress’ blogger changes his Permalink-Type, because the site’s PHP-Scripts are generating URLs as references to its own components, the blogger is mainly changing what type of permalinks the site is generating. But in general, the rewrite rules and CGI-Scripts are flexible enough, to parse any of them, if they arise as a URL. Only, what the scripts are also coded to do is recognize, If the requested URL is using a different type of permalink, from the currently-selected type. If so, the script makes sure that a permalink of the current type displays in the browser’s URL-field.

The reason this is done, is the fact that some readers will actually use the current URL which the browser sees, when they Copy and Paste URLs, and in this case the blogger would rather have it as well, that his currently-chosen type of permalinks are received by the reader.

This can be accomplished, when the server sends to browser an HTML-page which is mainly empty, except for a Header, which instructs the browser to request a redirect, with a time-delay of zero (= Client-Pull).

Dirk

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