Additional expressiveness for relation entities

[NicolasRouquette]

Key axiom support for 'oml:hasSource' or 'oml:hasTarget' or both.

Given:

concept A
concept B
relation entity R [
  from A
  to B
  forward r
]

There could be different key axioms for R as shown below. Additionally, one could assert additional key axioms for other properties.

1. the source without the target

relation entity R [
  from A
  to B
  forward r
  key oml:hasSource
]

2. the target without the source

relation entity R [
  from A
  to B
  forward r
  key oml:hasTarget
]

3. the source and the target

relation entity R [
  from A
  to B
  forward r
  key oml:hasSource, oml:hasTarget
]

Cardinality restrictions on oml:hasSource, oml:hasTarget or both

Given:

concept A
concept B
concept B1 :> B
concept B2 :> B
concept B3 :> B

relation entity R [
  from A
  to B
  forward r
]

There could be cardinality restrictions like this:

relation entity R [
  from A
  to B
  forward r
  restricts all relation oml:hasTarget to max 1 B1
  restricts all relation oml:hasTarget to min 2 B2
  restricts all relation oml:hasTarget to max 0 B3
]