Is XML really more semantic that HTML with classes/ids? - html

Question

I'm coming from a HTML / JavaScript / PHP background and have recently started learning XML.
I was reading this excerpt from "No Nonsense XML Web Development with PHP" which includes this comparison:
<div>
<div>
<h2>Product One</h2>
<p>Product One is an exciting new widget that will simplify your life.</p>
<p><b>Cost: $19.95</b></p>
<p><b>Shipping: $2.95</b></p>
</div>
</div>
Take a good look at this – admittedly simple – code sample from a computer’s perspective. A human can certainly read this document and make the necessary semantic leaps to understand it, but a computer couldn’t. ....
A computer program (and even some humans) that tried to decipher this document wouldn’t be able to make the kinds of semantic leaps required to make sense of it. The computer would be able only to render the document to a browser with the styles associated with each tag. HTML is chiefly a set of instructions for rendering documents inside a Web browser; it’s not a method of structuring documents to bring out their meaning.
The author then compares this to XML with this:
If the above document were created in XML, it might look a little like this:
<productListing title="ABC Products">
<product>
<name>Product One</name>
<description>Product One is an exciting new widget that will simplify your life.</description>
<cost>$19.95</cost>
<shipping>$2.95</shipping>
</product>
</productListing>
In theory, we should be able to look at any XML document and understand instantly what’s going on. In the example above, we know that a product listing contains products, and that each product has a name, a description, a price, and a shipping cost. You could say, rightly, that each XML document is self-describing, and is readable by both humans and software.
I get the author's point to a degree. Of course a computer would not be able to discern meaning from this HTML, there's no context.
However, I would never expect the HTML to be written in this way. Rather I would expect the HTML to use classes and/or ids to provide the necessary context more like:
<div class="productListing">
<div class="product">
<h2 class="name">Product One</h2>
<p class="description">Product One is an exciting new widget that will simplify your life.</p>
<p class="cost"><b>Cost: $19.95</b></p>
<p class="shipping"><b>Shipping: $2.95</b></p>
</div>
</div>
Given this example, my question is:
Is XML really more semantic than HTML that utilizes classes/ids to provide context to the data it contains?
(Note that I simplified the code examples to avoid TL;DR)

Answer 1

This is an interesting question.I'll give you my two cents.
I jumped onto XML a few years ago when I had to built a dynamic website and my client didn't have access to the database(just FTP access).What I essentially coded was an XML backend and PHP which fetched this through SimpleXML parsing.
In retrospect, I do think XML is more semantically richer than HTML. As a comment pointed out above, the html class has been a styling construct. I don't remember personally using/ hearing anyone using classes or ids for purposes other than CSS/JS based styles or animations.
The key in using XML over HTML with classes was the flexibility to throw it around. For another project, updating values of XML elements from one system, and then having them read and displayed by an other system made a lot of things smoother.Additionally, the XML parsing libraries allow a number of functions for parsing through the nodes.
Also it's important to note that XML allows you to define attributes.This could be viewed as something similar to classes and ids to HTML.
Also, let's not forget that RSS feeds are essentially XML and not HTML with more tags.
Therefore, answering your question specifically with respect to semantic, I definitely think XML has the advantage there.
TLDR:XML is more semantic according to me

Answer 2

You are correct that in terms of just looking at markup, there is little do none difference between XML's "meaningful" element names, and HTML class/id. However, keep in mind that for XML, there is a set of technologies and tools that allow you to easily work with element names. You can write schemas and validate against them. You can compose schemas by using namespaces. You can extract structures by using simple XPath expressions. All of this is much harder with the HTML approach.
So if you have requirements to capture and process "meaningful" structures, then XML is your friend. If all you want is to have snapshot of something where you can say "this is a product", then maybe there really might be not such a big difference.
My advice would be: If you store and process data using multiple publishing pipelines, XML very likely is a much better starting point. If all you want is capture snapshots that will get delivered to HTML-based consumers, then "semantically enriched" HTML may be the easier way to go.