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Goals & Criteria

  • Broadly approachable
  • Hit the ground running
  • Interoperable
  • Scalable and forward-looking
  • Fits the approach of the Fluid community: functional, declarative, Web-oriented

A broadly approachable services layer technology lets us reach out to a large number of Web developers, allowing them to get involved in the Engage community and technology using skills and languages they may already be familiar with. Similarly, the Fluid community itself needs to hit the ground running with Engage, building the services layer in technologies that are familiar and will get us coding with minimum ramp-up time.

Interoperability is a primary goal of Engage, ensuring that our technologies will work with a wide range of existing authoring tools, content management systems, and other tools commonly found in museums and on the Web. The Engage services layer needs to fit in well and leverage open standards wherever possible.

At the same time, our choice for server-side technology needs to be scalable and forward-looking, allowing museums to invest in Engage over long run, without fear that our services will slow down impossibly when confronted with large collections, and that they won't quickly go obsolete.

Lastly, the Fluid community has built up, over the years, a set of techniques and philosophies for writing software: accessibility, the Open Web, functional programming, and markup agnosticism are common themes throughout our technologies. As a community, we embrace diversity and a wide range of styles; shared patterns and techniques in code help make our solutions more coherent and consistent to develop with.

Candidates We Considered

We explored a variety of potential technologies for the Engage services layer. In each case, we considered both a programming language and an accompanying Web framework, recognizing that much of the advantage of a particular language comes from good tools we can reuse. Here's a list of the options we considered:

  • PHP
  • Ruby + Merb
  • Python + CherryPy
  • Server-side JavaScript: a) JVM + Servlets + JSGI, and b) V8CGI or other next-generation runtime + Apache module

We explored each of these options through a series of conversations with the Engage development team and the wider Fluid community. An in-depth set of notes and ideas from these conversations is available at the Fluid Engage Server-side Technology page.

Some Background Thinking

< intro to the process >

Our evaluation wasn't particular scientific, though we did perform some fairly comprehensive performance benchmarks as we started to narrow down our choices. In general, our process involved carefully examining both the features and the context of a particular technology: what it has to offer both in terms of technical solutions as well as the associated community, documentation, and support.

Many of the most familiar Web framework, regardless of language, tend to take a roughly similar approach to structuring code along the lines of Model, View, and Controller (MVC). This particular style of Web MVC can broadly be described as Rails-inspired, and is shared by technologies such as Django, Merb, and others. In short, this approach tends have the following characteristics:

  • Models, or entities, have a direct mapping to database tables through a object/relation mapping layer
  • Views are HTML templates and the associated code required to map and render the model
  • Controllers fill in the glue between this, providing various other responsibility including URL routing

In context of Engage, this approach has a number of weakness. With the schema-less approach...

While much has been said about the alternative MVC approach we've taken in Infusion...

  • MVC and the proliferation of controllers
  • Goal of ubiquity
  • Infrastructure and being at the bleeding edge

JavaScript on the Server

Portability and JSGI

Next Generation Runtimes

Rhino and the JVM

Tying it all Together

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