When an investigator submits a paper to a journal for publication she/he has to sign an agreement with the journal that states that the journal essentially "owns" the paper and the data contained in the paper. Once the paper is published in the journal, can the data be posted on-line as well? And, if the raw data appeared on-line prior to the publication of the paper, can the publisher refuse to publish the paper claiming that the "paper has already been published?"
The initial answer is these questions is it depends on what the journal contract says. Initially, the researcher owns the data due to copyright rules. But she/he could sign these rights over to someone else (if they aren't careful.) But the picture is not as simple as this looks since what the researcher publishes is not the original data, but an analysis of the data. The rights to the analysis "data" contained in the paper oftentimes is signed over to the publisher but the raw data are still owned by the researcher. Also, because much of our funds comes from Federal sources, we are obligated to follow the Federal rules about making the raw data collected with these funds publicly available, as soon as possible, and usually no later than two years after collecting/processing.
Many publishers do no permit web sites to download an article from the publisher's web site and reserve that article from their own web server. If the article has a digital object identifier (doi) one can access the article's abstract via http://dx.doi.org/. Depending on the specific agreement between the requester and the publisher, the article may be available on-line as well, or the requester will be given the opportunity to buy a copy of the article from the publisher.
For information about how to include a data citation in your paper, click here.