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Only a few annotation types have been defined so far, but as the number of tasks grow, we can look for common behavior that can be signaled by annotation. For example, there is a @Mutative type: that tells CS that the task may alter (mutate) the object it is working on.

Scripted Tasks

DSpace 1.8 includes limited (and somewhat experimental) support for deploying and running tasks written in languages other than Java. Since version 6, Java has provided a standard way (API) to invoke so-called scripting or dynamic language code that runs on the java virtual machine (JVM). Scripted tasks are those written in a language accessible from this API. The exact number of supported languages will vary over time, and the degree of maturity of each language, or suitability of the language for curation tasks will also vary significantly. However, preliminary work indicates that Ruby (using the JRuby runtime) and Groovy may prove viable task languages.

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For reasons of portability, the <relFilePath> component may be omitted in this context. Thus, "$td=ruby||LinkChecker.new" will be expanded to a descriptor with the name of the embedding file.

Interface

Scripted tasks must implement a slightly different interface than the CurationTask interface used for Java tasks. The appropriate interface for scripting tasks is ScriptedTask and has the following methods:

public void init(Curator curator, String taskId) throws IOException;
public int performDso(DSpaceObject dso) throws IOException;
public int performId(Context ctx, String id) throws IOException;

The difference is that ScriptedTask has separate perform methods for DSO and identifier. The reason for that is that some scripting languages (e.g. Ruby) don't support method overloading.

performDso() vs. performId()

You may have noticed that the ScriptedTask interface has both performDso() and performId() methods, but only performDso is ever called when curator is launched from command line.

There are a class of use-cases in which we want to construct or create new DSOs (DSpaceObject) given an identifier in a task. In these cases, there may be no live DSO to pass to the task.
You actually can get curation system to call performId() if you queue a task then process the queue - when reading the queue all CLI has is the handle to pass to the task. 

Starter Tasks

DSpace 1.7 bundles a few tasks and activates two (2) by default to demonstrate the use of the curation system. These may be removed (deactivated by means of configuration) if desired without affecting system integrity. Each task is briefly described here.

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