I wrote:
On the other hand, there are full automated methods, which don't involve user interaction. the unsupervised approach is feasible if the goal is to extract from a huge number of Web resources.
I didn't use "on one hand" before it, I just want to introduce a comparison with the supervised (semi-automated) methods which involve user interaction and has described in the previous paragraph.
Is my usage correct? especially that I used "on the other hand, there are …", should I say something like "on the other side, there are …" or "on the other end, there are …"?!
Best Answer
"On the other hand" is a common idiom to introduce a competing or contrasting ideas. While you certainly CAN say, "On one hand ... on the other hand ...", it is not necessary.
PS This reminds me of the review of a book by Peter Schickele that says, "On the one hand, Peter Schickele is very funny. On the other hand, he wears a ring." You may need to read that a couple of times.