"Domain Graph" [1] was renamed to "Multilayer Graphs" [2].
The "Multilayer Graphs Model" was aimed to address the limitations found in prior Graph Models (e.g. RDF, Property Graphs) in representing higher-arity graphs without having to resort to reification or reserved words/vocab.
Skipping over the formal math definitions, a Multi-Layer Graph, in practical terms, is represented by statements of "quads": "{edge id, source, label, target}" -- similar on the surface to RDF-named graphs, but not.
The source and target may also refer other edges in addition to referring to the "entities" of real-world-concepts; targets may also be data types (e.g. strings, ints, etc)-- I believe that MilleniumDB puts edges, sources, targets and some simple values under the same packed int64 namespace.
Useful for MilleniumDB under-the-hood design/architecture, and probably for Wikidata where their data model are qualified facts-- a qualifying statement (e.g. "valid from 2020 to 2024") about a factual statement ("Alice Lived in America").
But this is just me, a non-expert, trying to cut to the core points after discovering and reading the papers just recently since knowledge graphs are hot topics right now.
allowing edges to have edges is something that RDF* allows.
Property graphs DBs like Neo4j don't support it but you can do it by using a node as a relationship. This is called a metanode or a hypernode. The need for this is mitigated somewhat by the fact that property graphs allow edges to have properties themselves. so you would use
The "Multilayer Graphs Model" was aimed to address the limitations found in prior Graph Models (e.g. RDF, Property Graphs) in representing higher-arity graphs without having to resort to reification or reserved words/vocab.
Skipping over the formal math definitions, a Multi-Layer Graph, in practical terms, is represented by statements of "quads": "{edge id, source, label, target}" -- similar on the surface to RDF-named graphs, but not.
The source and target may also refer other edges in addition to referring to the "entities" of real-world-concepts; targets may also be data types (e.g. strings, ints, etc)-- I believe that MilleniumDB puts edges, sources, targets and some simple values under the same packed int64 namespace.
Useful for MilleniumDB under-the-hood design/architecture, and probably for Wikidata where their data model are qualified facts-- a qualifying statement (e.g. "valid from 2020 to 2024") about a factual statement ("Alice Lived in America").
But this is just me, a non-expert, trying to cut to the core points after discovering and reading the papers just recently since knowledge graphs are hot topics right now.
[1] https://arxiv.org/abs/2111.01540 [2] https://users.dcc.uchile.cl/~ahogan/docs/mutlilayer_graphs.p...