1. A method of separating a set of related documents, the method comprising: determining, on a document selection system, quality scores for a plurality of the documents in the set of related documents based on comparisons with a predetermined value; obtaining a similarity score for a plurality of pairs of documents in the set of related document; and on the document selection system, obtaining a first subset of related documents which solves an optimization problem, the first subset of related documents being a subset of the set of related documents, the optimization problem being a function of one or more quality scores of the documents assigned to the first subset of related documents and one or more similarity scores of pairs of documents assigned to the first subset of related documents, wherein the optimization problem maximizes an evaluation function and wherein the evaluation function is: f ⁡ ( A ) = ∑ v ∈ V ⁢ ⁢ u v ⁡ ( v , A ⁡ ( v ) ) + ∑ v 1 , v 2 ∈ E ⁢ ⁢ u E ⁡ ( v 1 , v 2 , A ⁡ ( v 1 ) , A ⁡ ( v 2 ) ) where v is a document, A(v) is a labelling function which assigns a document, v, to either the first subset of related documents or a second subset of related documents, V is the set of related documents, u v (v,A(v)) is a function of the quality score of a document v, E is a set of all pairs of documents and u E (v 1 ,v 2 ,A(v 1 ),A(v 2 )) is a function of the similarly score between document v 1 and v 2 .
1. A method of separating a set of related documents, the method comprising: determining, on a document selection system, quality scores for a plurality of the documents in the set of related documents based on comparisons with a predetermined value; obtaining a similarity score for a plurality of pairs of documents in the set of related document; and on the document selection system, obtaining a first subset of related documents which solves an optimization problem, the first subset of related documents being a subset of the set of related documents, the optimization problem being a function of one or more quality scores of the documents assigned to the first subset of related documents and one or more similarity scores of pairs of documents assigned to the first subset of related documents, wherein the optimization problem maximizes an evaluation function and wherein the evaluation function is: f ⁡ ( A ) = ∑ v ∈ V ⁢ ⁢ u v ⁡ ( v , A ⁡ ( v ) ) + ∑ v 1 , v 2 ∈ E ⁢ ⁢ u E ⁡ ( v 1 , v 2 , A ⁡ ( v 1 ) , A ⁡ ( v 2 ) ) where v is a document, A(v) is a labelling function which assigns a document, v, to either the first subset of related documents or a second subset of related documents, V is the set of related documents, u v (v,A(v)) is a function of the quality score of a document v, E is a set of all pairs of documents and u E (v 1 ,v 2 ,A(v 1 ),A(v 2 )) is a function of the similarly score between document v 1 and v 2 . 7. The method of claim 1 , wherein the quality score for a document is determined based on a number of times the document has been shared.