The National Science Digital Library maintain a wiki on how they manage metadata. Here’s list of the types of learning resources that can be defined in IEEE LOM 5.2:Educational.LearningResourceType (and presumably if you’re using Dublin Core, DC.Type).
Now on one level this is a good thing. When creating a metadata record for a learning resource, knowing in advance how other people describe their learning resources helps you to decide how to describe yours. For example, if you upload a learning resource to a repository and declare that it’s of type ‘video’ by adding ‘video’ to the object’s 5.2:Educational.LearningResourceType metadata, then if everyone else uses ‘video’ rather than ‘movie’ to for all similar objects, pretty soon we’d get a lot of consistency and it’d be easy to search for all the videos in the repository. That’s the benefit of controlled vocabulary metadata, we select keywords from a predefined list. Selecting from a limited list of predefined types of objects works well when there are clearly distinct types of objects.
Where it gets tricky however is with resources whose type is not obvious. For example, from the NSDL’s own list, two adjacent terms, ‘project’ and ‘proposal’, two aspects of the same thing. A proposal defines a project, but is the proposal always distinct from the project itself? Plus more fundamentally if you disagree with definition of either of these types of object, which type, if any, should you use? It’s not easy to decide.
Another more fundamental problem with such a list of types of resources is that they often mix the form or format of a resource with its educational purpose. For example, ‘video’ tells me something about the data format, but ‘assessment’ tells me nothing about the data format but tells me a lot about what educational context it might be used for. Can an assessment contain a video for example? Probably. So there’s yet another problem. Aggregations of content can be very difficult to define when they contain multiple data formats. For example multimedia learning resources, should they be described in terms of their technical format, or their educational format, or both?
So, is there merit in creating a controlled vocabulary of types of learning resources or should the user be allowed to define their own type? Well, before you decide one way or another, consider the mine-field presented by the different subject domains. Any list that you can come up with someone will always come up with a type of resource that you hadn’t though of. So rather than attempt to define the empirical list of learning resource types, let the user enter whatever keywords best describe their resource. Like will attract like and soon enough people working in the same domain will be able to find resources of interest. Perhaps too much of what makes metadata difficult for many are the enforced choices a user has to make when describing their resource. Let the content creator decide based on their own professional judgement and maybe we’ll get more descriptive metadata being created voluntarily.