5 Reference Metadata
- Contents
5.1 Scope of the Metadata Structure Definition (MSD)
The scope of the MSD is reduced in SDMX 3.0, by means of simplifying its structure, but also in the way referenced Artefacts are targeted. In fact, the MSD is restricted to play the role of a single container, without targeting any specific Artefact. The possible targets of Metadata Set are specified in the Metadataflows or Metadata Provision Agreements relating to that MSD. To achieve that, the structure of the Metadataflow has changed in this version of the standard. Moreover, the Metadata Provision Agreement Artefact is introduced to include this feature.
Two more changes, introduced in this version, are the following:
- The Metadata Set becomes a Maintainable Artefact but maintained by a Metadata Provider (another new Artefact in this version).
- Metadata Attributes may also be used in Data Structure Definitions, as long as the latter reference the Metadata Structure Definition that specify those Metadata Attributes.
5.2 Identification of the Object(s) to which the Metadata is to be attached
The following example shows the structure and naming of the MSD and related components for creating reference metadata.
The schematic structure of an MSD is shown below.
Figure 1: Schematic of the Metadata Structure Definition
The MSD contains one Metadata Attribute Descriptor comprising the Metadata Attributes that identify the Concepts for which metadata may be reported in the Metadata Set. The Metadataflow and Metadata Provision Agreement comprise the specification of the objects to which metadata can be reported in a Metadata Set (Metadata Target(s)).
The high-level view of the MSD, as well as the way the Metadataflow and Metadata Provision Agreement specify the Targets:
Figure 2: The high-level view of the MSD containing one Metadata Attribute Descriptor
Figure 3: Wildcarded Target Objects as specified in a Metadataflow
Figure 4: Specific Target Objects as specified in a Metadata Provision Agreement
Note that the SDMX-ML schemas have specific XML elements for each identifiable object type because identifying, for instance, a Maintainable Object has different properties from an Identifiable Object which must also include the agency, Id, version, and id of the Maintainable Object in which it resides.
5.3 Metadata Structure Definition
An example is shown below.
Figure 5: Example MSD showing specification of some Metadata Attributes
This example shows the following hierarchy of Metadata Attributes:
- Contact – this is presentational; no metadata is expected to be reported at this level
- Contact Name
- Address – this is also presentational; up to 3 addresses are allowed
- House Number
5.4 Metadata Set
An example of reporting metadata according to the MSD described above, is shown below.
Figure 6: Example Metadata Set
This example shows:
- The reference to the Metadata Provision Agreement and Metadata Target
- The reported metadata attributes (AttributeSet)
- Reference Metadata in Data Structure Definition and Dataset
An important change of SDMX 3.0 is the ability to reference an MSD within a DSD, in order to report any Metadata Attributes defined in the former to Datasets of the latter.
This is achieved by the following:
- In a DSD, the user may add a reference to one MSD.
- In the Attribute Descriptor of the DSD, the user may include any Metadata Attributes defined in the linked MSD.
- For each link to a Metadata Attribute, an Attribute Relationship may be specified (similarly to that for Data Attributes).
- In any Dataset complying with this DSD, Metadata Attributes may be reported according to the specified Attribute Relationship.
- The hierarchy of the Metadata Attributes defined in the MSD must be respected and they are reported in the same way as in a Metadataset, under the level they are related within the DSD, via their Attribute Relationship.
- In Data Constraints, the user is allowed to restrict values for Metadata Attributes, in the same way as Data Attributes (more on this in section “10 Constraints”).