20. The media of claim 19 , further comprising instructions that when executed by the at least one processor cause the at least one processor to: identify a relevance of a content item retrieved using the topic to perform a per interest retrieval to be the relevance value reflecting the strength of relationship between the topic and the content item; and identify a relevance of a content item retrieved in a group interest retrieval using the remaining topics, the identified relevance being identified using a cosine similarity between the remaining topics' relevance values, each relevance value corresponding to one of the remaining topics and reflecting the strength of relationship between the remaining topic and the content item.
20. The media of claim 19 , further comprising instructions that when executed by the at least one processor cause the at least one processor to: identify a relevance of a content item retrieved using the topic to perform a per interest retrieval to be the relevance value reflecting the strength of relationship between the topic and the content item; and identify a relevance of a content item retrieved in a group interest retrieval using the remaining topics, the identified relevance being identified using a cosine similarity between the remaining topics' relevance values, each relevance value corresponding to one of the remaining topics and reflecting the strength of relationship between the remaining topic and the content item. 21. The media of claim 20 , the instructions that when executed by the at least one processor cause the at least one processor to rank further comprising instructions that when executed by the at least one processor cause the at least one processor to: rank the retrieved content item in order of each content item's identified relevance.