The IndeGx vocabulary has two goals:
- To extend Manifest and VoID to make it possible to express complex rules for metadata generation by the IndeGx engine.
- To define resources for the expression of metadata about endpoints and datasets that are not available in well-known vocabularies.
The details of the vocabulary are presented on a dedicated page.
The declaration of extraction rules follows the structure described in the following schema. In color are the elements defined by the IndeGx vocabulary.
The elements of the metadata generation rules are called generation assets, and are instances of kgi:GenerationAsset. They are organized in a tree-like structure. Each generation asset can be applied by the IndeGx engine, either by the application of a list of other generation assets it contains of by the application of SPARQL queries it contains.
The application of a generation asset can be put on hold and wait for the application of other assets before being applied. This condition is expressed as a list of generation assets objects of the property kgi:requiredAssets. Note that the usage of this property makes it possible to declare loops in the tree-like structure of the generation assets. Currently, there is no mechanism to detect and prevent loops in the IndeGx engine.
Metadata generation rules are centered around the definition of a manifest, by convention with a file name containing manifest. The manifest always contains one instance of mf:Manifest. This instance may give a list of sub-manifests as object of the mf:include property. It also may give the list of entries it will apply as the object of the property mf:entries.
Entries are instances of mf:ManifestEntry and earl:TestCase. By convention, their URIs correspond to the address of an RDF file which contains the description of the test associated with the entry. The generation assets that are applied depending on the result of the test are listed as objects of the properties kgi:onSuccess and kgi:onFailure.
The test can be either an instance of kgi:TestQuery or kgi:DummyTest. A kgi:TestQuery instance must give a SPARQL query as the object of kgi:query and it can precise an endpoint to send the query to different from the one being treated. A test instance of kgi:DummyTest represents a test that always succeeds.
Actions are instances of kgi:Action. In the tree-like structure of the metadata generation rules, they are the leaf nodes. An action must give a SPARQL query as the object of the property mf:action. By convention, the action is generally a blank node. The SPARQL query is the one that will be executed by the IndeGx engine to generate the metadata. By convention, it is a SPARQL UPDATE query or a CONSTRUCT query. As for the test, the action can precise an endpoint to send the query to different from the one being treated using kgi:endpoint. An action can also precise the timeout allocated to the execution of the query, as the object of the property kgi:timeout. The action can also give the IndeGx engine a size of pagination to apply to the query, as the object of the property kgi:recommendedPagination.