NLP: What is expected from the output of a perfect coreference system? For instance, consider the following piece of text:
'The father of Richard is a very nice guy. He was born in a poor family. Because of that, Richard learnt very good values. Richard is also a very nice guy. However, Richard's mother embarasses the family. She was born rich and she does not know the real value of the money. She did not have to be a hard worker to succeed in life.&quot;
How should a perfect coreference should work? Is this solution the perfect solution?
Cluster 1:
'The father of Richard' (first sentence) &lt;-&gt; 'He' (second sentence)

Cluster 2:
'Richard' (third sentence) &lt;-&gt; 'Richard' (forth sentence)

Cluster 3:
'Richard\'s mother' (fifth sentence) &lt;-&gt; She (sixth sentence) &lt;-&gt; she (sixth sentence) &lt;-&gt; She (seventh sentence)  

If I use the coreference library of spacy (neuralcoref), I get these clusters:
Clusters:
[Richard: [The father of Richard, He, Richard, Richard, Richard], a poor family: [a poor family, the family], Richard's mother: [Richard's mother, She, she, She]]

Note that this output says that &quot;Richard&quot; is the same for sentences that is true. However, &quot;He&quot; in the second sentence is not related to &quot;Richard&quot;, but to his father. Also &quot;Richard&quot; and the &quot;Father of Richard&quot; are together in the same cluster. Furthermore, &quot;poor family&quot; and &quot;family&quot; should not come together. However, this is realy difficulty since in this case there is some level of ambiguity.'
I know that this is a very difficult problem. The point is not criticize this fantastic library. I am just trying to understand what I should expect as perfect result.
If I change a little the text:
'The mother of Richard is a very nice woman. She was born in a poor family. Because of that, Richard learnt very good values. Richard is a very nice guy. However, Richard's father embarasses the family. He was born rich and he does not know the real value of the money. He did not have to be a hard worker to succeed in life.'
The clusters are:
[Richard: [The mother of Richard, She, Richard, Richard, Richard, He, he, He], a poor family: [a poor family, the family]]

In this case, the clusters become stranger, since &quot;She&quot; and &quot;Richard&quot; are in the same cluster. Furthermore, the &quot;He&quot; related to the &quot;father of Richard&quot; belongs to the cluster, but not &quot;Richard's father&quot;.
So, my question is:
What is the perfect result that I should expect from a &quot;perfect&quot; coreference system?
The clusters you mentioned at the beginning seem right. A &quot;perfect&quot; coreference system should be able to find all words/phrases that refer to the same object.
However, in language, there will always be some ambiguity. For example, consider the sentences &quot;Bob and John like building. He has fun doing it.&quot;. It is ambiguous whether &quot;He&quot; refers to &quot;Bob&quot; or &quot;John&quot;. In that sense, a perfect coreference system may not even exist theoretically. If it did, it would either avoid classifying &quot;He&quot; or recognize that it could go with either &quot;Bob&quot; or &quot;John&quot;.