RE: RDB structure to RDF mapping

On Apr 19, 2016 9:07 AM, "Pete Rivett" <pete.rivett@adaptive.com> wrote:

> You should be aware that, if you’re trying to represent real world
databases, the situation can get complex since a Key may consist of many
Columns. And the same Column may be part of many Foreign Keys and also part
of the Primary Key.

Thanks to the wonders of RDF, representing compound/composite keys isn't
that much harder than handling simple keys.  Or to put it another way,
handling simple keys isn't much easier :)

In both cases, a link between  two tables needs to be represented as an
instance, because it needs to have properties asserted about it (lo - a
graph database :)

For simple keys one can  use a pair of single valued properties to store
the columns to join on.

For compound (or composite) keys you can extend this by e.g. representing
the compound keys as instances in themselves;  keeping a list of pairs of
columns (or keeping two lists of columns); or having a multivalued property
where each value is a pair of columns.

The performance costs of any of these approaches is unlikely to be
significant for sane collections of RDBMS schemata. Fortunately we have ORM
tools to avoid this.
Since rdf lists involve cdr chasing, this can be a performance drain
depending on the particular triple store implementation. Using a
multivalued property may be faster.

Simon