Ojo Philip - There are many conditions which must be looked into for a conference proceedings and/or conference paper before publishing it again. 1) If only an abstract is published then there is no problem 2) Adding some more results with more details and without any plagiarism with a major change is usually acceptable. 3) Taking permissions from the publisher and authors. However, a word of caution is that if it is published in book form as full paper then we cannot submit it to any journal.
Ojo Philip - There are many conditions which must be looked into for a conference proceedings and/or conference paper before publishing it again. 1) If only an abstract is published then there is no problem 2) Adding some more results with more details and without any plagiarism with a major change is usually acceptable. 3) Taking permissions from the publisher and authors. However, a word of caution is that if it is published in book form as full paper then we cannot submit it to any journal.
A paper published already could be presented in a conference (if their guideline allows). Often done by researchers, a published paper in a conference that contains up to 30% of new idea is publishable in an indexed journal. Again, some papers presented in a conference have reference citation and this is done from personal previously published work , most times.
The two way round here, as they are two faces, are plausible. Earlier discussions here as well;
1. To be sincere with you, a paper presented in a conference and you no that the paper will be published in a conference proceeding then it can not be published again.
2. There is what is called an extended paper: that is paper published from conference presentation, then the paper will be publish in a journal after the authors must have effects almost 50% changes in the paper, starting from the, title; abstract; introduction; methodology; result and conclusion. When this is excellently done the authors can published it in a journal.