forked from D-Net/openaire-graph-docs
29 lines
1.5 KiB
Markdown
29 lines
1.5 KiB
Markdown
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# Merge by id
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In the metadata aggregation system it is common to find the same record provided by
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different datasources and, sometimes, even inside the same datasource (especially in
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case of aggregators). As the harmonisation processes are performed per datasource
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contents, the relative records are the output of different mapping implementations.
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This approach has the advantage to be deeply customisable to catch datasource specific
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aspects, but it leaves room for inconsistencies when evaluating the different mappings
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across the various datasources.
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This phase is therefore responsible to compensate for such inconsistencies and performs
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a global grouping of every record available in the graph:
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- entities are grouped by [`id`](../data-model/entities/result#id)
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- relations are grouped by [`source`, `target`, `reltype`](../data-model/relationships/relationship-object)
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This ensures that the same record, possibly assigned to different types by different
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mappings, appears only once in the graph and under a single typing. In case of clashing
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identifiers, the properties are merged (including the provencance information), considering
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the following precedence order for the result typing:
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```
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publication > dataset > software > other
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```
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The same holds for relationships, as the same (e.g.) DOI-to-DOI citation relation could
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be aggregated from multiple sources, this grouping phase would collapse all the different
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duplicates onto a single relation that would however include all the individual provenances.
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