Magnus Manske wrote:
How about: <newpagetemplate title="ISSN 12345">some_template|12345</newpagetemplate>
which links to a special page with the contents (dynamically generated) {{some_template|12345}}
This discussion is very interesting and could potentially lead to something very powerful and useful. However, it seems like the novel concept needs some time to mature, first being developed as a separate Mediawiki module, then tested on separate wikis, before at last being deployed on Wikipedia.
For the more immediate need, is it possible to just double the existing Special:Booksources page to be used for ISSNs? As I pointed out in my first posting in this thread, it doesn't require any changes to the wiki syntax or parser. The new special page would just be linked to from the Template:ISSN. That's all.