How can a database derived from copyrighted works be public domain?
<p>I've been using the website <a href="http://RefractiveIndex.INFO" rel="nofollow">RefractiveIndex.INFO</a> to get some optical constants for a physics project.</p>

<p>It seems like all the graphs reference a book or some source for the data they contain. For example, the most popular one would probably be for water (<a href="http://refractiveindex.info/?shelf=main&amp;book=H2O&amp;page=Hale" rel="nofollow">located here</a>), which references <code>G. M. Hale and M. R. Querry. Optical Constants of Water in the 200-nm to 200-µm Wavelength Region, Appl. Opt. 12, 555-563 (1973)</code>.</p>

<p>When I read about the database <a href="http://refractiveindex.info/download.php" rel="nofollow">here</a>, the author says that he has released the database to the public domain. How can he do that if the data in this database is not really his own?</p>

<p>Also this leaves me unsure exactly how to cite the source. It feels odd to not include the authors of the actual data.</p>

<p>At least in the United States (and I'm pretty sure this is true around the world), facts and information cannot be copyrighted. Just because a work is copyrighted, doesn't mean every part of that work is copyrighted, and factual information conveyed by the work is a part which is not subject to copyright.</p>

<p>Copyright on a collection of facts is limited to the selection and arrangement of those facts, and only if that selection and arrangement has some bare minimum amount of originality. See <em>Feist v. Rural</em>, 499 U.S. 340. In this case, it looks at first glance like the person who made that site made their own selection of which materials and which sources would be included; the one place where they really seem to have copied their selection is from glass catalogs with datasheets from specific manufacturers, who would have a hard time arguing that "everything we manufacture in this widely-recognized class of substances" is an original selection. What the author of the website has done is relinquish <em>his</em> rights in <em>his</em> selection and arrangement of the data.</p>

<p>In some places, there are other rights besides copyright that do apply to databases; for instance, the EU recognizes database rights to protect significant investment in compiling a database of stuff. But the US does not have that concept.</p>

<p>For citing stuff, that's not really a legal question, and has more to do with academic standards. Ask your adviser or teacher if you have one.</p>

<p>Although a paper containing experimental data can be copyrighted, the data itself can not.</p>

<p>As for citing the original publication, it is completely up to you. It is not uncommon to cite a handbook or database containing a compilation of data from hundreds of sources rather than the original works.</p>

copyright public-domain