Adding an invisible reference: PI or <remark>?

I just made a small BibTeX-like system for DocBook which allows to
include in the bibliography only the referenced biblioentries (so the
bibliography can be a comprehensive document, maintained separately,
and the output still stay small).

I would like to implement the ability to add a feature like the
\citeref of BibTex where the biblioentry is included even if there is
no visible reference to it. I wonder about the best markup. Advices
welcome.

1) A PI like <?bibtex-like myentry>

2) <remark><xref linkend="myentry"/></remark>

3) Other solution?