XML is a cheap DSL

Given that that is had strong schema XSD verification built in, where you can tell in an instant whether or not the document is correct; it’s the right tool for a majority of jobs.

My experience has been the people complaining about it were simply not using automated tools to handle it. It’s be like people complaining that “binaries/assembly are too hard to handle” and never using a disassembler.

Re: XML is a cheap DSL

#5

Post by jgalt212 » Sat, Mar 14, 2026, 12:57 PM UTC

> Tax logic needs a declarative specification

preach. I'm convinced there are cycles in the tax code that can be exploited for either infinite taxes or zero taxes. Can Claude find them?

Re: XML is a cheap DSL

#6

Post by sgarland » Sat, Mar 14, 2026, 12:57 PM UTC

While a great article, I actually found this linked post [0] to be even better, in which the author lays out how so much modern tooling for web dev exists simply because XML lost the browser war.

EDIT: obviously, JSON tooling sprang up because JSON became the lingua franca. I meant that it became necessary to address the shortcomings of JSON, which XML had solved.

0: https://marcosmagueta.com/blog/the-lost-art-of-xml/

Re: XML is a cheap DSL

#7

Post by necovek » Sat, Mar 14, 2026, 12:58 PM UTC

XML is notoriously expensive to properly parse in many languages. Basically, the entire world centers around 3 open source implementations (libxml2, expat and Xerces), if you want to get anywhere close to actual compliance. Even with them, you might hit challenges (libxml2 was largely unmaintained recently, yet it is the basis for many bindings in other languages).

The main property of SGML-derived languages is that they make "list" a first class object, and nesting second class (by requiring "end" tags), and have two axes for adding metadata: one being the tag name, another being attributes.

So while it is a suitable DSL for many things (it is also seeing new life in web components definition), we are mostly only talking about XML-lookalike language, and not XML proper. If you go XML proper, you need to throw "cheap" out the window.

Another comment to make here is that you can have an imperative looking DSL that is interpreted as a declarative one: nothing really stops you from saying that

  totalOwed = totalTax - totalPayments
  totalTax = tentativeTaxNetNonRefundableCredits + totalOtherTaxes
  totalPayments = totalEstimatedTaxesPaid +
                      totalTaxesPaidOnSocialSecurityIncome +
                      totalRefundableCredits

means exactly the same as the XML-alike DSL you've got.

One declarative language looking like an imperative language but really using "equations" which I know about is METAFONT. See eg. https://en.wikipedia.org/wiki/Metafont#Example (the example might not demonstrate it well, but you can reorder all equations and it should produce exactly the same result).

Re: XML is a cheap DSL

#8

Post by raverbashing » Sat, Mar 14, 2026, 1:03 PM UTC

Honestly let's leave XML in that 90s drawer from where it should have never left

Re: XML is a cheap DSL

#9

Post by badgersnake » Sat, Mar 14, 2026, 1:03 PM UTC

sgarland wrote: post #6

While a great article, I actually found this linked post [0] to be even better, in which the author lays out how so much modern tooling for web dev exists simply because XML lost the browser war. EDIT: obviously, JSON tooling sprang up because JSON became the lingua franca. I meant that it became necessary to address the shortcomings of JSON, which XML had solved. 0: https://marcosmagueta.com/blog/the-lost-art-of-xml…

It’s the usual case of “I can’t be bothered to learn the complicated thing, give me something simple.” Two years later, “Oh wait, I need more features, this problem is more complicated than I thought”.

Re: XML is a cheap DSL

#10

Post by necovek » Sat, Mar 14, 2026, 1:03 PM UTC

necovek wrote: post #7

XML is notoriously expensive to properly parse in many languages. Basically, the entire world centers around 3 open source implementations (libxml2, expat and Xerces), if you want to get anywhere close to actual compliance. Even with them, you might hit challenges (libxml2 was largely unmaintained recently, yet it is the basis for many bindings in other languages). The main property of SGML-derived languages is that…

FWIW, this is also one of the reasons MathML has never become the "input" language for mathematics, and the layout-focused (La)TeX remains the de-facto standard.

Ergonomics of input are important because they increase chances of it being correct, and you can usually still keep it strict and semantic enough (eg. LaTeX is less layout-focused than Plain TeX)