Monday, 30 November 2009

Disaggregation Models

~ This page describes how specific chapters, modules, units and pages of a course can be individually selected using the Icodeon Common Cartridge Platform ~

Disaggregation is used to describe how a collection of digital assets might be logically divided into smaller units.

There does not seem to be anything very controversial about that - but disaggregation has been the cause of more disagreement than you might expect.
A classic example of a disaggregation controversy occured with the disruptive introduction of digital music software, such as iTunes. The music industry wanted to sell a CD; the consumer wanted to buy an individual track. What was the right "unit of disaggregation"? Well, eventually the consumer's view prevailed: the individual track took precedence over the CD.

The e-Learning industry has had its own disaggregation controversy - by trying to figure out what the "unit of disaggregation" is for online learning: is it the course, the unit, the module, the activity? Or what? Most of this time this controversy is expressed in the debate about what a digital learning object is.

You might suppose that the World Wide Web might fall into it's own disaggregation controversy. After all, what is the unit of "unit of disaggregation" for the web? Is it a website? A web page? An image in a web page?

Interestingly, the World Wide Web neatly side-steps it's own disaggregation controversy with the concept of addressability: everything on the web MUST have a unique address - a URL - whether it is a website, a web page or an image. Look at these addresses:
  • http://www.website.com
  • http://www.website.com/webpage.html
  • http://www.website.com/images/image.gif
With the web, we do not need to concern ourselves too much with disaggregation, because what ever level of granularity we want to work with, we can construct an appropriate address.

The Icodeon Common Cartridge Platform follows the World Wide Web approach - and side-steps any disaggregation controversy by using a URL Language that supports addressability.

Look at this course about college Organic Chemistry, published by Pearson in IMS Common Cartridge format. You can see the entire cartridge here in the Icodeon Cartridge Explorer.



There is the entire cartridge, subdivided into chapters, each of which have several pages.

Most instructors would probably want to use some of this material, but not all of it. So what is the "unit of disaggregation" that should be offered to the instructor?

The Icodeon Common Cartridge Platform makes this question redundant because the Platform URL Language can address the cartridge, or the chapter, or the page. Or a mix of these (a page from Chapter 1, and all of Chapter 2 - for example).

The choice is for the instructor to make - and it not limited by any technology decision.

To address a page, we use the URL Language like this:

http://{hostname}/cartridges/
{cartridge-name}/items/@first.json
That gives us a JSON representation of the first page in the cartridge. When mashed up with a blog, we end up with a single link:

~ Webcontent Launch Tool from Icodeon CC Platform ~

But what if we want a chapter, not a page? We just use the URL Language with an address including the chapter identifier, not the page identifier:
http://{hostname}/cartridges/
{cartridge-name}/items/{item-identifier}.json
That gives us a JSON representation of a chapter in the cartridge. When mashed up with a blog, we end up with a list of links:

~ Webcontent Launch Tool from Icodeon CC Platform ~

And if we want the whole course, not a chapter? We just use the URL Language that uses the root identifier:
http://{hostname}/cartridges/
{cartridge-name}/items/@root.json
That gives us a JSON representation of the whole course.When mashed up with a blog, we end up with a nested list of links:

~ Webcontent Launch Tool from Icodeon CC Platform ~

The instructor is free to choose what is included in e-Learning material: references to a course, a chapter or a page are all supported.

So by following the World Wide Web approach - and side-stepping any disaggregation controversy by using addressability - the Icodeon Common Cartridge Platform puts the decision about the size of the learning object back where it belongs: in the professional judgement of the instructor.

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