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We alluded to the fact that the rule language used to select resources from resource keys was called a composition language. To briefly elucidate, some resource types have a natural (de)composability or combinability that CGI can usefully exploit. Let us take metadata templates as an example. Currently in DSpace, one can (optionally) define one template for any each collection. If defined, this template is applied by assigning the metadata values in the template to new items submitted to that collection. Conceptually, the set of values making up the template could be a combination (sum) of other templates, say one that is used for the collection, and one that is used for a given content type. RCL will give us the ability to do this declaratively:
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The situation with Ingest Resources is quite different, as noted above: current DSpace practice (which basically all derives from configurable submission) is to encode resource data in an XML file, which is parsed at runtime (typically by an affiliated 'Reader' helper class) to create immutable (read-only) access objects. In this sense, there is no resource persistence problem, since XML disk files are quite persistent. In fact, it is interesting to note that the same XML files typically also contain what CGI would call a resource map: that is, a set of values mapped to resource instances. These facts suggest a number of strategies for working with XML-based resources. We summarize each below, noting some costs and benefits. But it is quite important to understand first, that these strategies can be combined opportunistically, and second, that any strategy can be revisited or overturned as new developer resources or time permits. Past experience suggests that constraints on developer time and availability will require low-barrier strategies to be adopted initially, with more robust ones pursued later.
Grandfathering
In this case, we do (almost) nothing to the resource implementation itself. The existing Read
User Interface
It will have been observed that nothing has been said about end user interactions with CGI services or functionality. In part, this is due to the fact that CGI is really a set of infrastructure services for application code,