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0 pointsdmsnell1y ago0 comments

I’ve become quite a fan of writing in SGML personally, because much of what you note is spot-on. Some of the points seem a bit of a stretch though.

Any type-checking inside of SGML is more akin to unused-variable checking. When you say that macros/entities may contain parameters, I think you are referring to recursive entity expansion, which does let you parameterize macros (but only once, and not dynamically within the text). For instance, you can set a `&currentYear` entity and refer to that in `copywrite "&currentYear/&currentDay`, but that can only happen in the DTD at the start of the document. It’s not the case that you could, for instance, create an entity to generate a Github repo link and use it like `&repoName = "diff-match-patch"; &githubLink`. This feature was used in limited form to conditionally include sections of markup since SGML contains an `IGNORE` “marked section”.

   <!ENTITY % private-render "IGNORE">
   ...
   <![%private-render[
   <side-note>
   I’m on the fence about including this bit.
   It’s not up to the editorial standards.
   </side-note>
   ]]>

SGML also fights hard against stream processing, even more so than XML (and XML pundits regret not deprecating certain SGML features like entities which obstruct stream processing). Because of things like this, it’s not possible to parse a document without having the entire thing from the start, and because of things like tag omission (which is part of its syntax “MINIMIZATION” features), it’s often not possible to parse a document without having _everything up to the end_.

Would love to hear what you are referring to with “safe” third-party transclusion and also what features are available for removal or rejection of undesired script in user content.

Apart from these I find it a pleasure to use because SGML makes it easy for _humans_ to write structured content (contrast with XML which makes it easy for software to parse). SGML is incredibly hard to parse because in order to accommodate human factors _and actually get people to write structured content_ it leans heavily on computers and software doing the hard work of parsing.

It’s missing some nice features such as namespacing. That is, it’s not possible to have two elements of the same name in the same document with different attributes, content, or meanings. If you want to have a flight record and also a list of beers in a flight, they have to be differentiated otherwise they will fail to parse.

   <flight-list>
   <flight-record><flight-meta pnr=XYZ123 AAL number=123>
   </flight-list>

   <beer-list>
   <beer-flight>
   <beer Pilsner amount=3oz>Ultra Pils 2023
   <beer IPA>Dual IPA
   <beer Porter>Chocolate milk stout
   </beer-list>

DSSSL was supposed to be the transforms into RSS, page views, and other styles or visualizations. With XML arose XSL/XSLT which seemed to gain much more traction than DSSSL ever did. My impression is that declarative transforms are best suited for simpler transforms, particularly those without complicated processing or rearranging of content. Since `osgmls` and the other few SGML parsers are happy to produce an equivalent XML document for the SGML input, it’s easy to transform an SGML document using XSL, and I do this in combination with a `Makefile` to create my own HTML pages (fair warning: HTML _is not XML_ and there are pitfalls in attempting to produce HTML from an XML tool like XSL).

For more complicated work I make quick transformers with WordPress’ HTML API to process the XML output (I know, XML also isn’t HTML, but it parses reliably for me since I don’t produce anything that an HTML parser couldn’t parse). Having an imperative-style processor feels more natural to me, and one written in a programming language that lets me use normal programming conveniences. I think getting the transformer right was never fully realized with the declarative languages, which are similar to Angular and other systems with complicated DSLs inside string attribute values.

I’d love to see the web pick up where SGML left off and get rid of some of the legacy concessions (SGML was written before UTF-8 and its flexibility with input encodings shows it — not in a good way either) as well as adopt some modern enhancements. I wrote about some of this on my personal blog, sorry for the plug.

https://fluffyandflakey.blog/2024/10/11/ugml-a-proposal-to-u...

Edit: formatting

0 comments

tannhaeuser1y ago

Nice to meet a fellow SGML fan!

> When you say that macros/entities may contain parameters, I think you are referring to recursive entity expansion,

No, I'm referring to SGML data attributes (attributes declared on notations having concrete values defined on entities of the respective notation); cf. [1]. In sgmljs.net SGML, these can be used for SGML templating which is a way of using data entities declared as having the SGML notation (ie. stand-alone SGML files or streams) to replace elements in documents referencing those entities. Unlike general entities, this type of entity expansion is bound to an element name and is informed of the expected content model and other contextual type info at the replacement site, hence is type-safe. Data attributes supplied at the expansion site appear as "system-specific entities" in the processing context of the template entity. See [2] for details and examples.

Understanding and appreciating the construction of templating as a parametric macro expansion mechanism without additional syntax may require intimate knowledge of lesser known SGML features such as LPDs and data entities, and also some HyTime concepts.

> create an entity to generate a Github repo link

Templating can turn text data from a calling document into an entity in the called template sub-processing context so might help with your use case, and with the limitation to have to declare things in DTDs upfront in general.

> it’s not possible to parse a document without having the entire thing from the start, and because of things like tag omission (which is part of its syntax “MINIMIZATION” features), it’s often not possible to parse a document without having _everything up to the end_.

Why do you think so and why should this be required by tag inference specifically? In sgmljs.net SGML, for external general entities (unlike external parameter entities which are expanded at the point of declaration rather than usage), at no point does text data have to be materialised in its entirety. The parser front-end just switches input events from another external source during entity expansion and switches back afterwards, maintaining a stack of open entities.

Regarding namespaces, one of their creators (SGML demi-good James Clark himself) considers those a failure:

> the pain that is caused by XML Namespaces seems massively out of proportion to the benefits that they provide (cf. [3]).

In sgmljs.net SGML, you can handle XML namespace mappings using the special processing instructions defined by ISO/IEC 19757-9:2008. In effect, element and attributes having names "with colons" are remapped to names with canonical namespace parts (SGML names can allow colons as part of names), which seems like the sane way to deal with "namespaces".

I haven't checked your site, but most certainly will! Let's keep in touch; you might also be interested in sgmljs.net SGML and the SGML DTD for modern HTML at [4], to be updated for WHATWG HTML review draft January 2025 when/if it's published.

Edit:

> Would love to hear what you are referring to with “safe” third-party transclusion and also what features are available for removal or rejection of undesired script in user content.

In short, I was mainly referring to DTD techniques (content models, attribute defaults) here.

[1]: https://sgmljs.net/docs/sgmlrefman.html#data-entities

[2]: https://sgmljs.net/docs/templating.html

[3]: https://blog.jclark.com/2010/01/xml-namespaces.html

[4]: https://sgmljs.net/docs/html5.html

dmsnellOP1y ago

Took me a while to process your response; thanks for providing to so much to think about. And yes, it is indeed nice meeting other SGML enthusiasts!

Can’t say I’m familiar with the use of notations the way you are describing, and it doesn’t help that ISO-8879-1986 is devoid of any reference to the italicized or quoted terms you’re using. Mind sharing where in the spec you see these data attributes?

The SGML spec is hands-down the most complicated spec I’ve ever worked with, feeling like it’s akin to how older math books were written before good symbolic notation was developed — in descriptive paragraphs. The entire lack of any examples in the “Link type definition” section is one way it’s been hard to understand the pieces.

> some HyTime concepts

I’m familiar with sgmljs but have you incorporated HyTime into it? That is, is sgmljs more like SGML+other things? I thought it already was in the way it handles UTF-8.

> Why do you think so and why should this be required by tag inference specifically?

Perhaps it’d be clearer to add chunkable to my description of streaming. Either the parser gets the document from the start and stores all of the entities for processing each successive chunk, or it will mis-parse. The same is true not only for entities for also for other forms of MINIMIZATION and structure.

Consider encountering an opening tag. Without knowing that structure and where it was previously, it’s not clear if that tag needs to close open elements. So I’m contrasting this to things that are self-synchronizing or which allow processing chunks in isolation. As with many things, this is an evaluation on the relative complexity of streaming SGML — obviously it’s easier than HTML because HTML nodes at the top of a document can appear at the end of the HTML text; and obviously harder than UTF-8 or JSON-LD where it’s possible to find the next boundary without context and start parsing again.

> Regarding namespaces, one of their creators (SGML demi-good James Clark himself) considers those a failure:

Definitely aware of the criticism, but I also find them quite useful and that they solve concrete problems I have and wish SGML supported. Even when using colons things can get out of hand to the point it’s not convenient to write by hand. This is where default namespacing can be such an aid, because I can switch into a different content domain and continue typing with relatively little syntax.

Of note, in the linked reference, James Clark isn’t arguing against the use of namespaces, but more of the contradiction between what’s written in the XML and the URL the namespace points to, also of the over-reliance on namespacing for meaning in a document.

What feels most valuable is being able to distinguish a flight of multiple segments and a flight of different beers, and to do so without typing this:

  <com.dmsnell.things.liquids.beer.flight>
    <com.dmsnell.things.liquids.beer.beer>

  <com.dmsnell.plans.travel.itineraries.flight>
    <com.dmsnell.plans.travel.flights.segment>

Put another way, I’m not concerned about the problem of universal inter-linking of my documents and their semantics across the web, but neither was SGML.

Cheers!

tannhaeuser1y ago

Get a copy of The SGML Handbook! It includes the ISO 8879 text with much needed commentary. The author/editor deliberately negotiated this to get some compensation for spending over ten years on SGML; it's meant to be read instead of the bare ISO 8879 text.

Regarding HyTime, the editor (Steven Newcomb or was it Elliot Kimber?) even apologized for its extremely hard-to-read text, but the gist of it is that notations were used as a general-purpose extension mechanism, with a couple of auxiliary conventions introduced to make attribute capture and mapping in link rules more useful. sgmljs templating uses these to capture attributes in source docs and supply the captured values as system-specific entities to templates (the point being that no new syntax is introduced that isn't already recognized and specced out in HyTime general facilities). The concept and concrete notations of Formal System Identifiers is also a HyTime general facility.

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0 pointsdmsnell1y ago0 comments

I’ve become quite a fan of writing in SGML personally, because much of what you note is spot-on. Some of the points seem a bit of a stretch though.

   <!ENTITY % private-render "IGNORE">
   ...
   <![%private-render[
   <side-note>
   I’m on the fence about including this bit.
   It’s not up to the editorial standards.
   </side-note>
   ]]>

Would love to hear what you are referring to with “safe” third-party transclusion and also what features are available for removal or rejection of undesired script in user content.

   <flight-list>
   <flight-record><flight-meta pnr=XYZ123 AAL number=123>
   </flight-list>

   <beer-list>
   <beer-flight>
   <beer Pilsner amount=3oz>Ultra Pils 2023
   <beer IPA>Dual IPA
   <beer Porter>Chocolate milk stout
   </beer-list>

https://fluffyandflakey.blog/2024/10/11/ugml-a-proposal-to-u...

Edit: formatting

0 comments

tannhaeuser1y ago

Nice to meet a fellow SGML fan!

> When you say that macros/entities may contain parameters, I think you are referring to recursive entity expansion,

> create an entity to generate a Github repo link

Regarding namespaces, one of their creators (SGML demi-good James Clark himself) considers those a failure:

> the pain that is caused by XML Namespaces seems massively out of proportion to the benefits that they provide (cf. [3]).

Edit:

> Would love to hear what you are referring to with “safe” third-party transclusion and also what features are available for removal or rejection of undesired script in user content.

In short, I was mainly referring to DTD techniques (content models, attribute defaults) here.

[1]: https://sgmljs.net/docs/sgmlrefman.html#data-entities

[2]: https://sgmljs.net/docs/templating.html

[3]: https://blog.jclark.com/2010/01/xml-namespaces.html

[4]: https://sgmljs.net/docs/html5.html

dmsnellOP1y ago

Took me a while to process your response; thanks for providing to so much to think about. And yes, it is indeed nice meeting other SGML enthusiasts!

> some HyTime concepts

I’m familiar with sgmljs but have you incorporated HyTime into it? That is, is sgmljs more like SGML+other things? I thought it already was in the way it handles UTF-8.

> Why do you think so and why should this be required by tag inference specifically?

> Regarding namespaces, one of their creators (SGML demi-good James Clark himself) considers those a failure:

What feels most valuable is being able to distinguish a flight of multiple segments and a flight of different beers, and to do so without typing this:

  <com.dmsnell.things.liquids.beer.flight>
    <com.dmsnell.things.liquids.beer.beer>

  <com.dmsnell.plans.travel.itineraries.flight>
    <com.dmsnell.plans.travel.flights.segment>

Put another way, I’m not concerned about the problem of universal inter-linking of my documents and their semantics across the web, but neither was SGML.

Cheers!

tannhaeuser1y ago

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