I’ll be attending PloneConf this year again, giving a talk about Deliverance. I’ve been working on Deliverance lately for work, but the hard part about it is that it’s not obviously useful. To help explain it I wrote the philosophy of Deliverance, which I will copy here, to give you an idea of what I’ve been doing:

Why is Deliverance? Why was it made, what purpose does it serve, why should you use it, how can it change the way you do web development?

On the Subject of Platforms Right now we live in an age of platforms. Developers (or management or coincidence) decides on a platform, and that serves as the basis for all future development. Usually there’s some old things from a previous platform (or a primordial pre-platform age: I’m looking at you formmail.pl !) The goal is always to eliminate all of these old pieces, rewriting them for the new platform. That goal is seldom attained in a timely manner, and even before it is accomplished you may be moving to the next platform. Why do you have to port everything forward to the newest platform? Well, presumably it is better engineered. The newest platform is presumably what people are most familiar with. But if those were the only reasons it would be hard to justify a rewrite of working software. Often the real push comes because your systems don’t work together. It’s hard to keep templates in sync across all the platforms. Multiple logins may be required. Navigation is inconsistent and incomplete. Functionality that cross-cuts pages — comments, login status, shopping cart status, etc — isn’t universally available. A similar conflict arises when you consider how to add new functionality to a site. For example, you may want to add a blog. Do you: Use the best blogging software available? Use something native to your platform? Write something yourself? The answer is probably 2 or 3, because it would be too hard to integrate something foreign to your platform. This form of choice means that every platform has some kind of “blog”, but the users of that blog are likely to only be a subset of the users of the parent platform. This makes it difficult for winners to emerge, or for a well-developed piece of software to really be successful. Platform-based software is limited by the adoption of the platform. Not all software has a platform. These tend to be the most successful web applications, things like Trac, WordPress, etc. “Aha!” you think “I’ll just use those best-of-breed applications!” But no! Those applications themselves turn into platforms. WordPress is practically a CMS. Trac too. Extensible applications, if successful, become their own platform. This is not to place blame, they aren’t necessarily any worse than any other platform, just an acknowledgment that this move to platform can happen anywhere.

Beyond Platforms, or A Better Platform One of the major goals of Deliverance is to move beyond platforms. It is an integration tool, to allow applications from different frameworks or languages to be integrated gracefully. There are only a few core reasons that people use platforms: A common look-and-feel across the site. Cohesive navigation. Indexing of the entire site. Shared authentication and user accounts. Cross-cutting functionality (e.g., commenting). Deliverance specifically addresses 1, providing a common look-and-feel across a site. It can provide some help with 2, by allowing navigation to be more centrally managed, without relying purely on per-application navigation (though per-application navigation is still essential to navigating the individual applications). 3, 4, and 5 are not addressed by Deliverance (at least not yet). Deliverance applies a common theme across all the applications in your site. It’s basic unit of abstraction is HTML. It doesn’t use a particular templating language. It doesn’t know what an object is. HTML is something every web application produces. Deliverance’s means of communication is HTTP. It doesn’t call functions or create request objects . Again, everything speaks HTTP. Deliverance also allows you to include output from multiple locations. In all cases there’s the theme, a plain HTML page, and the content, whatever the underlying application returns. You can also include output from other parts of the site, most commonly navigation content that you can manage separately. All of these pieces can be dynamic — again, Deliverance only cares about HTML and HTTP, it doesn’t worry about what produces the response. This is all very similar to systems built on XSLT transforms, except without the XSLT , and without XML. Strictly speaking you can apply XSLT to any parseable markup, even HTML, but the most common (or at least most talked about) way to apply XSLT is using “semantic” XML output that is transformed into HTML. Deliverance does not try to understand the semantics of applications, and instead expects them to provide appropriate presentation of whatever semantics the underlying application possesses. Presentation is more universal than semantics. While Deliverance does its best to work with applications as-they-exist, without making particular demands on those applications, it is not perfect. Conflicting CSS can be a serious problem. Some applications don’t have very good structure to work with. You can’t generate any content in Deliverance, you can only manipulate existing content, and often that means finding new ways to generate content, or making sure you have a place to store your content (as in the case of navigation). This is why arguably Deliverance does not remove the need for a platform, but is just its own platform. In so far as this is true, Deliverance tries to be a better platform, where “better” is “more universal” rather than “more powerful”. Most templating systems are more powerful than Deliverance transformations. It can be useful to have access to the underlying objects used to procude the markup. But Deliverance doesn’t give you these things, because it only implements things that can be applied to any source of content. Static files are entirely workable in Deliverance, just as any application written in Python, PHP, or even an application hosted on an entirely separate service is usable through Deliverance.