Why is the scientific citation index a reform of the traditional retrieval system?

1. Firstly, the traditional retrieval system provides retrieval approaches from the perspectives of author, classification and subject.

2. Secondly, the scientific citation index provides a new retrieval way from another angle, that is, from the perspective of the relationship between references.

3. Finally, the authors of the cited papers in these scientific citation indexes are used as a new starting point to find more cited papers, which is a change to the traditional retrieval system.