What is the requirement for submitting a revised workshop paper to a conf in CS? We have published a workshop paper last year. Now, we are planning to submit it to a conference. The conference paper roughly have 50% new materials. Basically, the workshop paper studied a 3.5-year data set while the conf version extends it to 4.5-year. The conf version also has a new data set. We also applied several new analysis methods to the data, obtaining new results.

My question is, is 50% new material enough for a new conference publication? Also, can I reuse the analysis methods in the workshop paper? What about reusing some text?

Thank you very much!

Update: Based on the valuable answers and comments from the community, I think a good approach to handle this is issue is to carefully cite our previous work for any content that is originated from it. Therefore, we make a clear distinction between old stuff and new stuff. But a trick thing is anonymity. We probably can only cite our previous work anonymously in the submission, otherwise the reviewers can easy tell the paper is from us...

We will also consult the conference for more information.
Depends on the specific workshop and conference.

Some workshops (if they are small events at bigger conferences, and if they don't publish the proceedings) don't count as prior publication, so you can use all the material again.

Some workshops are actually more like a regular conference, but use the name workshop.  So you should treat it as prior publication.

I suspect from your question that it is more the former.  I would suggest asking the papers chair for the conference;  if the workshop is related, they are probably familiar with it.