Monday, May 25, 2009

ReStructured Text markup and Content Management

I can't say enough good things about ReStructuredText (RST).  I've used all of the available markup languages (SGML, HTML and XML).  They have their place, but they all fall short of being truly usable.

In This sounds complicated, because it is I reviewed some of my history of cheap content management.   

In looking at content of all kinds, I'm finding that RST is much, much easier to work with than SGML, HTML or XML.  In short, I think that RST makes the file system into a really good content management system (CMS).  Unstructured content is a big win.  Structured content is a "don't care".  But there's a middle ground of semi-structured content that requires sophisticated semantic markup.

SGML At The Dawn Of Time

When the web started it's ascent (back in the 90's), I was lucky.  I had already been working with folks that did military contracting, and folks there had introduced me to SGML.   When I moved from SGML to HTML, I saw it as a pleasant simplification because it had a more-or-less fixed DTD.  

My first personal web pages were lovingly hand-crafted HTML masterpieces.  (Okay, they were lovingly hand-crafted.)   There was  a lot of work involved in markup, cross-references, and presentation. 

HTML via a Class Hierarchy

My first templating was via proper Python classes.  I created class hierarchies that embodied the page template and filled in required data.  The heart of each class was an emit method that wrote the final HTML.

Variant page layouts and special cases were easily handled by Python simple inheritance.  

Of course, the big problem is that HTML is just representation.  There's often some bleed-through between the problem domain model and the HTML representation of that underlying model.  You don't want your problem domain objects to encode any HTML.  You can have a generic Tag class, but the Page class is specific to your problem domain.

The Python class structure is nice, but it's only suitable for structured content management.  When you have semi-structured and unstructured data -- the strong suit of HTML -- you find the class hierarchy to be too rigid.

Some time in the early 00's, I discovered Cheetah.

HTML via Templates

Cheetah (and template engines like Mako, Jinja, and numerous others) did what I wanted.  A base template was -- effectively -- a superclass.  Each block in that template could be overridden by a subclass.

The content, then, becomes a relatively simple template file that extends a page layout.  You can handle unstructured and semi-structured content very nicely.  I changed my ways of working with HTML to leverage this elegant, extensible view of the world.  I redid my personal web site: the content become a collection of Cheetah templates that contained all the content.

Note that I've *added* a markup language.  In addition to HTML, I also have some Cheetah markup on each page.  While this got me consistency and flexibility (and a reduction in the volume of stuff on each page) it did make things slightly more complex.

Look at for another example of an all-Cheetah static site.  I did several sites like this.  The workflow involved (1) design the overall page, (2) getting the data into a usable form, (3) generating the page-level template files, and (4) running Cheetah to emit HTML from the templates.  All static content.  Runs like lightning.  

The JSP Distraction

Eventually, I started doing development with Struts, which depends heavily on JSP.  You have HTML commingled with Java code.  Plus, you've got custom actions via a tag library to extend JSP processing.  You can create page-level templates with a reasonably smart JSP tag library.

This template solution doesn't work well for unstructured or semi-structured data.  It's a pure programming solution.

DocBook XML and Semantic Markup

I wrote Building Skills in Python entirely in Appleworks.  That was pretty well unmaintainable and unpublishable in that form.

I converted the text to DocBook XML.  I used the Leo outliner to manage the document as a whole.  I wrote my own publishing workflow to transform the XML to HTML and PDF.   It worked reasonably well.

More important, using DocBook reinforced the importance of semantic markup.  It took me back to my SGML days.  It also showed why and other HTML presentation things have to be moved out of the document and into the stylesheet.

This was a very nice way to handle the semi-structured and unstructured content in a book.  Direct use of XML is a pain in the neck.  XML has a lot of syntax.  It's much nicer to do your thinking with something lighter weight.  

ReStructured Text (RST) for Unstructured Content

Somewhere in the late 00's, I found Python's docutils and RST.  I can't figure out when I started -- precisely -- but using RST as part of content management didn't fully click at first.

After reworking my personal site, which includes a lot of really unstructured ("random" might be a better word) content, I'm seeing the value in RST + Filesystem as a CMS.  I think the Sphinx folks are right.  If you have a simple markup system and all the filesystem tools that have evolved over the past few decades, you're covered.

Further, on larger projects, I've found that I can pop out a nice template documentation tree with a simple .. toctree:: directive on the index.rst page and generate a tidy, complete documentation package without much pain.

Structured Content

For structured data, you have ordinary classes and programs.  You have SQL databases, ORM to map to classes; all of that technology.  It's easy to write applications that emit RST which you can then publish.  

Most structured content can be boiled down to tables and charts.  The .. csv-table:: directive makes it easy to have an application emit data that you fold into a more elegant-looking report.

The Nuance -- Semi-Structured Data

My worst-case scenarios are my résumés: sailing, programming and writing.  The data has deep semantic meaning:  it isn't just words.  On the other hand, the data has lots of special-cases and exceptions: it isn't totally amenable to a database.

The absolute best part of docutils is that the parser's output is available for processing.  You can -- easily -- add directives and text roles to create semantic meaning.

I experimented with XML and YAML for my résumés.  The XML is cumbersome.  The YAML requires a fairly sophisticated class model to make use of the information.  

RST with a few text roles, however, rocks.  The .. role:: directive makes it easy to throw roles into a document for later use by applications.


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