SDB does not have a single database layout. This page is an informal overview of the two main types (“layout2/hash” and “layout2/index”).
In SDB one store is one RDF dataset is one SQL database.
Databases of type layout2 have a triples table for the default graph, a quads table for the named graphs. In the triples and quads tables, the columns are integers referencing a nodes table.
In the hash form, the integers are 8-byte hashes of the node.
In the index form, the integers are 4-byte sequence ids into the node table.
Triples
+-----------+ | S | P | O | +-----------+
Primary key: SPO
Indexes: PO, OS
Quads
+---------------+ | G | S | P | O | +---------------+
Primary key: GSPO
Indexes: GPO, GOS, SPO, OS, PO.
Nodes
In the index-based layout, the table is:
+------------------------------------------------+ | Id | Hash | lex | lang | datatype | value type | +------------------------------------------------+
Primary key: Id
Index: Hash
Hash:
+-------------------------------------------+ | Hash | lex | lang | datatype | value type | +-------------------------------------------+
Primary key: Hash
All character fields are unicode, supporting any character set, including mixed language use.