Links

URI vs. URL: What's the Difference?

URI

A URI identifies a resource either by location, or a name, or both. More often than not, most of us use URIs that defines a location to a resource. The fact that a URI can identify a resources by both name and location has lead to a lot of the confusion in my opionion. A URI has two specializations known as URL and URN.

URN

A URI identifies a resource by name in a given namespace but not define how the resource maybe obtained. This type of URI is called a URN. You may see URNs used in XML Schema documents to define a namespace, usually using a syntax such as:

<xsd:schema xmlns="http://www.w3.org/2001/XMLSchema"
            xmlns:xsd="http://www.w3.org/2001/XMLSchema"
            targetNamespace="urn:example"

Here the targetNamespace use a URN. It defines an identifier to the namespace, but it does not define a location.

URL

A URL is a specialization of URI that defines the network location of a specific resource. Unlike a URN, the URL defines how the resource can be obtained. We use URLs every day in the form of http://damnhandy.com, etc. But a URL doesn’t have to be an HTTP URL, it can be ftp://damnhandy.com, smb://damnhandy.com, etc.

The Difference Between Them

So what is the difference between URI and URL? It’s not as clear cut as I would like, but here’s my stab at it:

A URI is an identifier for some resource, but a URL gives you specific information as to obtain that resource. A URI is a URL and as one commenter pointed out, it is now considered incorrect to use URL when describing applications. Generally, if the URL describes both the location and name of a resource, the term to use is URI. Since this is generally the case most of us encounter everyday, URI is the correct term.

Vannevar Bush's Memex

Every now and then, I like to revisit Vannevar Bush’s classic article from the July 1945 edition of the Atlantic Monthly called As We May Think in which he describes a theoretical machine called the memex.

A memex is a device in which an individual stores all his books, records, and communications, and which is mechanized so that it may be consulted with exceeding speed and flexibility. It is an enlarged intimate supplement to his memory.

It consists of a desk, and while it can presumably be operated from a distance, it is primarily the piece of furniture at which he works. On the top are slanting translucent screens, on which material can be projected for convenient reading. There is a keyboard, and sets of buttons and levers. Otherwise it looks like an ordinary desk.

1945! Apart from its analogue rather than digital nature, it’s a remarkably prescient vision. In particular, there’s the idea of “associative trails”:

Wholly new forms of encyclopedias will appear, ready made with a mesh of associative trails running through them, ready to be dropped into the memex and there amplified. The lawyer has at his touch the associated opinions and decisions of his whole experience, and of the experience of friends and authorities.

[…]

And now I’m using the World Wide Web, a hypermedia system that takes in the whole planet, to create an associative trail. In this post, I’m linking (without asking anyone for permission) to six different sources, and in doing so, I’m creating a unique associative trail. And because this post has a URL (that won’t change), you are free to take it and make it part of your own associative trail on your digital memex.

Tags

How to Disable Links

The topic of disabling links popped up at my work the other day. Somehow, a “disabled” anchor style was added to our typography styles last year when I wasn’t looking. There is a problem though: there is no real way to disable an <a> link (with a valid href attribute) in HTML. Not to mention, why would you even want to? Links are the basis of the web.

At a certain point, it looked like my co-workers were not going to accept this fact, so I started thinking of how this could be accomplished. Knowing that it would take a lot, I wanted to prove that it was not worth the effort and code to support such an unconventional interaction, but I feared that by showing it could be done they would ignore all my warnings and just use my example as proof that it was OK. This hasn’t quite shaken out for me yet, but I figured we could go through my research.

First, things first:

Just don’t do it.

A disabled link is not a link, it’s just text. You need to rethink your design if it calls for disabling a link.

[…]

Surefire way: remove the href

If you have decided that you are going to ignore my warning and proceed with disabling a link, then removing the href attribute is the best way I know how.

Straight from the official Hyperlink spec:

The href attribute on a and area elements is not required; when those elements do not have href attributes they do not create hyperlinks.

An easier to understand definition from MDN:

This attribute may be omitted (as of HTML5) to create a placeholder link. A placeholder link resembles a traditional hyperlink, but does not lead anywhere.

See the source link on more complex stuff involving disabling click/tap/keyboard interactions via JavaScript.

But sometimes links look like buttons (and buttons look like links)

In Resilient Web Design Jeremy Keith discusses the idea of material honesty. He says that “one material should not be used as a substitute for another, otherwise the end result is deceptive”.

Making a link look like a button is materially dishonest. It tells users that links and buttons are the same when they’re not.

In Buttons In Design Systems Nathan Curtis says that we should distinguish links from buttons because “button behaviours bring a whole host of distinct considerations from your simple anchor tag”.

For example, we can open a link in a new tab, copy the address or bookmark it for later. All of which we can’t do with buttons.