I have the following codes:

```
ItemSimilarity itemSimilarity = new UncenteredCosineSimilarity(dataModel); 
recommender = new GenericItemBasedRecommender(dataModel,itemSimilarity);
List<RecommendedItem> items = recommender.mostSimilarItems(10, 5);

```

my datamodel is like this:
uid itemid socre

```
userid itemid score
  1    6    5
  1   10    3
  1   11    5
  1   12    4
  1   13    5
  2   2     3
  2   6     5
  2   10    3
  2   12    5

```

when I run the code above,the result is just like this:
 13
 6
 11
 2
 12
I debug the code,and find that the  *List items = recommender.mostSimilarItems(10, 5);* return the items has the same score,that is one!
so,I have a problem.in my opinion,I think the mostsimilaritem should consider the item co-occurrence matrix：

```
    2   6   10  11  12  13

2   0   1   1   0   1   0

6   1   0   2   1   2   1

10  1   2   0   1   2   1

11  0   1   1   0   1   1

12  1   2   2   1   0   1

13  0   1   1   1   1   0

```

in the matrix above ,the item 12's most similar should be [6,12,11,13,2],because the item 1 and item 12 is more similar than the other items,isn't it? 
now,anyone who can explain this for me?thanks!