For large applications, we would recommend RDF whenever there is
significant variability of schema, but would still use an
application-specific, relational style representation for those
parts of the data that are regular in format. This is possible
without loss of flexibility for the variable-schema part. However,
this will introduce relational-style restrictions on the regular
data; for example, a person could only have a single date-of-birth
by design. In many cases, such restrictions are quite acceptable.
Querying will still take place in SPARQL, and the representation
will be transparent.
A relational table where the primary key is the RDF subject and
where columns represent single-valued properties is usually called
a property table. These can be defined in a manner similar to
defining RDF mappings of relational tables.