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3.4 Using the GeoViQua schemas

The root element of the producer metadata document should be a GVQ_Metadata element. The root element of user‐submitted data should be a GVQ_FeedbackCollection containing one or more GVQ_FeedbackItem elements.

When producer and user quality information are to be aggregated using a brokering approach, the document returned may take the form of a GVQ_Metadata element containing 0 or more GVQ_FeedbackCollection elements named ‘userFeedback’.

The design which permits this is shown in Figure 25.

GVQ_Metadataelement.png

Figure 25. A GVQ_Metadata element may contain 0 or more GVQ_FeedbackCollection elements

      

Because GVQ_Metadata is substitutable for MD_Metadata, this permits a collection of producer and user metadata to be returned as the content of a CSW catalogue response.

    3.4.1 Dataset and unique resource identifiers

    Unique dataset/resource identifies are vital to correctly connect producer data to user quality information. This is also crucial when dataset relationships are documented hierarchicaly, and thus all quality information that a particual dataset has also contains quality information inherited by its 'parent' dataset. A big concern is on how these unique identifiers are going to be maintained and updated.

      3.4.1.1 Recommended practice for recording dataset identifiers

      Many GeoViQua quality elements contain unique identifiers for datasets, encoded as MD_Identifier elements. The origin and maintenance of these unique identifiers is outside the scope of GeoViQua, but since it is a problem that affects GeoViQua in the ability to relate the quality elements to datasets, GeoViQua is stimulating the debate about metadata and data identifiers in GEOSS as an AIP5 technical activity12. It is assumed that there will be some option available composed of a code / codespace combination. In order to be compliant with INSPIRE’s URI mappings, it is recommended that this information is recorded in an MD_Identifier element using the codespace and code elements, as shown below:

      Codespace.png

      3.4.1.2 Identifiers - uniqueness and canonicalization

      The target is not really intended to be defined within the model. Potentially the target should solve the problem of creating referenceable hierarchies and could be shared with other models, i.e. from a feedback perspective it merely establishes the context that really lives outside in GEOSS.

      It has been decided that, for the purpose of modelling feedback, the existence of a globally unique identifier for the referenced resources can be postulated.

      As far as we could determine, that is not the case within GEOSS. For prototyping and evaluation that may be acceptable, but in future we will need to make use of a service of some kind which is capable of resolving dataset identifiers.

      3.4.1.3 Identifiers - Granularity

      Not every feedback target can be assumed to have an identifier, because GEOSS datasets are of mixed granularity. As a result, targets need to be able to discern concepts that are accumulated at the granularity that can be identified using well‐defined identifiers. In other words, it may well be necessary to specify how resources which are known to exist can be identified in a “synthetic” manner to allow feedback submission and discovery.

      For example, a dataset may be organized into layers which do not have a GEOSS identifier. To be able to target such a layer, the targets should be equipped with a locally unique (i.e. within the dataset) layer identifier (e.g. a name) and a parent target which contains the actual GEOSS identifier (possibly canonicalized).

          


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