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Comment by wendroid | Hacker News Reader

I always use the same example as why I dislike XML so much

    <a>
        <b>hi</b>
    </a>

is not the same as

    <a><b>hi</b></a>

But Erik Naggum makes the argument against XML so much more fun

http://harmful.cat-v.org/software/xml/s-exp_vs_XML

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How are those two examples different? Every XML system I've used would see those as the same.

I, however, really enjoyed this line from the link. "I once believed that it would be very beneficial for our long-term information needs to adorn the text with as much meta-information as possible. I still believe that the world would be far better off if it had evolved standardized syntactic notations for time, location, proper names, language, etc, and that even prose text would be written in such a way that precision in these matters would not be sacrificed, but most people are so obsessively concerned with their immediate personal needs that anything that could be beneficial on a much larger scale have no chance of surviving."

This wonderfully, succinctly explains why efforts like the semantic web are doomed to failure.

Technically, they are different. In the first example, there's whitespace between <a> and <b> as well </b> and </a>. Most applications ignore whitespace but they're not required to - whitespace is not ignored in XML.

I just died a little inside. Knowing that there are people out there that would inflict this kind of nonsense as a standard for others to use makes one really lose faith in humanity.

That's the only way to distinguish

  an <strong>emphasized</strong> word

from

  an<strong>emphasized</strong>word

Which makes perfect sense for documents. So why do we use a markup language suitable for documents for general data? Whitespace matters in a document, but does not matter for data. (I'm not accusing you, I'm actually curious if you know the answer. I've never had to deal with XML.)

It's an excellent question. My answer is, use XML for data if you need features that come with it, such as validation, or if you'll want to use it with tools/standards that orbit XML, like XQuery, or if you have a situation where you're dealing with both documents and data, and you want them to interoperate. Otherwise there's probably not a lot of benefit to XML; JSON, YAML, or a DSL will suit you just fine.

A lot of XML-hate comes from its overuse—it comes with overhead that is too expensive for simple cases, but is pretty useful when you go beyond simple. Right tool for the right job and all that...

It may matter a lot for some data... When you send a binary file, would you like all of the zeros stripped? Your insignificant data from one perspective is possiblely significant from another perspective.

It is not possible to ship binary over XML. Regardless of encoding used, XML rigidly forbids the bytes corresponding to non-whitespace ASCII chars below 32: http://www.w3.org/TR/2008/REC-xml-20081126/#charsets This makes arbitrary binary impossible. You have to base64 encode it or something.

Not entirely relevant to your point, but worth bringing up. (XML doesn't ever mangle binaries, because it simply forbids them.)

I don't follow. If you need literal, unstructured data embedded in a structured format, then use whatever escape mechanism the format has.

Because for the longest time there was nothing both better and standardized. I've dealt with xml many times and hate it but It's better than maintaining your own proprietary DTL.

Anyone who adopted JSON could have been using s-expressions all along, but it's become a tradition to ignore everything Lisp got right until some brave soul gives it a makeover with curly braces.

In theory, I'll agree with you. However, as far as I know, there are no s-exp parsing libraries for any language I know but Lisp. Also s-exps as they exist in Lisp assume some Lispish concepts that don't map to all languages. Symbols, for example, don't exist in Java. JSON is a better solution for cross language portability.

(sorry I want to reply to the reply but there's no reply button for it)

Saying there are no s-expression parsers for non-Lisp is ridiculous.

This one's http://sexpr.sourceforge.net/ for C, it's been in sourceforge since 2002.

perhaps you prefer one in :

Javascript - http://planet.plt-scheme.org/package-source/dherman/javascri...

Perl - http://search.cpan.org/~nelhage/Data-SExpression-0.34/lib/Da...

Limbo - http://man.cat-v.org/inferno/6/sexprs

I shan't go on

I didn't say that there weren't s-expression parsers for languages other than Lisp; just that I haven't found them. I'll be the first to admit that I haven't really been looking.

But you'll note the disparity in support. A library for parsing XML with C may have existed since 2002, but it's existed for XML since 97. In Java, XML support has been baked into the JVM for a while, but S-exp parsers are hard to find. That library you list for Javascript is not a s-exp parser but rather a Scheme library for generating Javascript from a Scheme-like language. Googling for javascript and s-exps returns a lot of results like that but not many s-expression parsers. There certainly aren't any widely used and recognized libraries like there are for XML and JSON fro most languages aside from Lisp.

The line breaks are classed as nodes (as is all whitepsace) unless you tell XML parsers to ignore them usually.

You're complaining that standard parsers give you extra information about the document being parsed? Another thing that might annoy you: even though comments are "ignored", many XML parsers generate comment nodes in the DOM. This allows you to produce an output document that is exactly equivalent to the input document.

If a node doesn't mean anything to your application, ignore it. If you're an XHTML parser, the whitespace is significant, so you need to handle it. If you're a FooML parser, the whitespace is insignificant, so just ignore it.

If you hate XML, this is not a particularly good justification.

I've become a JSON and YAML fan as I think they have higher signal to noise ratios (they each have their own issues with white space though).

  JSON:
  {"a":{"b":"hi"}}

  YAML:
  ---
  a:
    b: hi

In what contexts would those two snippets of XML be treated differently? (Not that I am jumping in to defend XML I'm just curious).

If you wrote code to crawl the tree generated from that XML, you'd have text nodes (of whitespace) in one, but not the other.

That's what I thought - I don't think I've ever seen an application that would bother with that difference.

You're using that application right now - XHTML takes the difference into consideration. Consider the <pre /> tag:

  <pre><b>Hello!</b></pre>

is rendered differently from

  <pre>
     <b>Hello!</b>
  </pre>

Good point! :-)

The difference is a big deal to applications that use XML as a markup language (marking up documents and text), as it was designed to do originally.

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