fail fast if there are no satisfiable solutions

@cmungall is already working on this.

Since Jul 11, 2023.

• #370 by @cmungall — open

Assume we start with:

```
A:1 A:2 0.1 0.0 0.0 0.0
B:2 B:1 0.1 0.0 0.0 0.0
A:1 B:1 0.0 0.0 1.0 0.0
A:2 B:2 0.0 0.0 1.0 0.0
```

this is the same as:

```owl
A:1 sub A:2
B:2 sub B:1
A:1 = B:1
A:2 = B:2
```

i.e. the relationship between 1 and 2 are flipped between A and B, yet they are equivalent. This is unsat if we add the

yields:

---

## SINGLETONS
Method: singletons
Score: 0.0
Estimated probability: 1.0
Confidence: 1.0
Subsequent scores (max 10):

- [A:2](http://example.org/A/2) EquivalentTo [B:2](http://example.org/B/2) (most probable) 1.0

---

Which is odd. It looks like it's rejecting p=1.0 axioms, but in fact it's accepting them:

```owl
Prefix(:=)
Prefix(owl:=)
Prefix(rdf:=)
Prefix(xml:=)
Prefix(xsd:=)
Prefix(rdfs:=)

Ontology(

Declaration(Class())
Declaration(Class())
Declaration(Class())
Declaration(Class())
Declaration(Class())
Declaration(Class())
############################
# Classes
############################

# Class: ()

SubClassOf( )
DisjointClasses( )

# Class: ()

SubClassOf( )
DisjointClasses( )

# Class: ()

EquivalentClasses( )
SubClassOf( )

# Class: ()

EquivalentClasses( )

# Class: ()

SubClassOf( )

)
```

which is unsat:

Reproduce the minimal ontology and singleton output described in the issue, then inspect the implementation associated with open pull request #370. Done means the unsatisfiable case is detected and fails fast instead of accepting the probability-1 axiom.

Written by the indexing model from the issue text.