A collection of resources. An aggregate can have any number of components.
Each component can be another aggregate, thus forming a tree of resources.
Different kinds of aggregate may exist for various reasons, for example (adapted from ISO 19115):
- Series: a generic collection of resources that share similar characteristics
(theme, date, resolution, etc.). The exact definition is determined by the data provider.
See
org.opengis.metadata.maintenance.ScopeCode#SERIES for more examples.
- Sensor series: a collection of resources observed by the same sensor.
- Platform series: a collection of resources observed by sensors installed on the same platform.
The
#components() of a platform series are sensor series.
Those components usually share the same geospatial geometry.
- Production series: a collection of resources produced using the same process. Members of a production
series share
org.apache.sis.metadata.iso.DefaultMetadata#getResourceLineages() and
org.apache.sis.metadata.iso.lineage.DefaultLineage#getProcessSteps().
- Initiative: a collection of resources related by their participation in a common initiative.
- Transfer aggregate: a set of resources collected for the purpose of transfer.
The
#components() may be the results of an ad hoc query, for example on a Web Service.
The same resource may be part of more than one aggregate. For example the same resource could be part of
a production series and a transfer aggregate. In Apache SIS implementation,
those two kinds of aggregate will usually be implemented by different
DataStore instances.
Metadata
Aggregates should have
#getMetadata() /
org.apache.sis.metadata.iso.DefaultMetadata#getMetadataScopes() /
org.apache.sis.metadata.iso.DefaultMetadataScope#getResourceScope() sets to
org.opengis.metadata.maintenance.ScopeCode#SERIES or
ScopeCode.INITIATIVE if applicable.
If not too expensive to compute, the names of all components should be listed as
org.apache.sis.metadata.iso.identification.AbstractIdentification#getAssociatedResources() with an
AssociationType.IS_COMPOSED_OF relation.