Presentation Management

Fabulator 0.0.9 is going to be full of changes. Some are relatively minor internal changes that only matter to people who have written tag libraries (i.e., me). The biggest change that will have an impact for you, the user, is the presentation layer management.

XML is at the heart of the Fabulator system. Applications are written in XML, libraries are written in XML. The views are written in whatever markup is comfortable, but the interactive elements (the forms) are easiest in XML.

Tag libraries will have two ways they can influence the system beyond defining types, functions, and actions. Tag libraries will be able to specify two different XSLTs: one that can be applied to the application to transform it, and one that can be applied in a presentation context to provide new presentation elements. The first can be used as a macro language for the applications. The second can be thought of as similar for presentations.

I’m considering using Fluid Infusion as the foundational JavaScript library for presentation. I’m not settled yet on which gem will get it, though it might be easiest to bundle it with the Radiant extension.

To add presentation transformations, you do something like the following in your Ruby tag library. This example is taken from the core action library.

Now the system knows which XSLT file to use when transforming the markup to HTML, it knows which elements in the tag library’s namespace should automatically be given default values and captions, and it knows which elements contribute their ‘id’ attribute to the path pointing to the default value in the application’s memory (and thus contribute to the name of the HTML input element as well).

You can have, for example, the following form in Radiant:

The name and email fields will be populated by the data in ‘/account/name’ and ‘/account/email’ if they exist. The HTML input fields will have the names ‘’ and ‘’.

The Radiant tag (<r:form />) automatically surrounds the enclosed XML in a <form xmlns=”http://…” /> element with the appropriate namespace declaration to allow simple form markup without prefixes.

Because different tag libraries may have structural elements that contribute to the path, the system will also inject a ‘path’ attribute into interactive elements so they know how to name the HTML elements. The tag library doesn’t have to know what other tag libraries are contributing.

It makes sense for one library to use another, so the XSLT associated with one library will be run before the XSLT associated with a library associated with a namespace mentioned in the library’s root element (for libraries defined in XML), or in the root element of the XSLT (for libraries defined in Ruby). This is for presentation and application XML transformations.

This is the start of a push away from explicit HTML in projects. We’ve done a lot to make the algorithms transportable through time — we don’t have to revisit projects to update code when we update the framework (or won’t once we hit 1.0), but there’s more to a project than just the algorithms. There’s also the HTML and CSS that tends to grow stale over time. By creating a presentation layer, we can capture the presentation intent of the project while providing a (hopefully) robust path forward.

Ultimately, a project may be able to expose the presentation and algorithm layers to advanced researchers and let them create their own algorithmic presentations built from humanities data. That’s a number of years off, but that’s the direction we’re headed.

Next on the todo list: come up with a reasonable set of presentation tags for building Exhibit displays. For those thinking this looks similar to things like Cacoon, you’re not too far off from the general idea as far as the implementation goes. Some details are a bit different, of course.