Numbering and cross-references

I am writing a large document (guess what) with chapter, section, subsection, subsubsection (and paragrph).

I have changed the numbering to fit my taste:

\setcounter{secnumdepth}{3} % Number subsubsections
\def\thechapter       {\Roman{chapter}}
\def\thesection       {\arabic{section}}
\def\thesubsection    {\thesection.\arabic{subsection}}
\def\thesubsubsection {\thesubsection.\arabic{subsubsection}}


This is nice but I have a problem. Suppose that in chapter II, I write a reference to section I.2. It will be rendered as 2 (ie, no chapter information).

Is there a way to deal with that?

P.S.: for details I use hyperref (the link points to the right section) and autoref.

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\def\thesection{\thechaper.\arabic{section}}? Or do you don't want your section titles also labeled "I.2" etc.? –  Martin Scharrer Jul 13 '11 at 16:31
Exactly: I don't want section titles labeled I.2 but I want references in the form I.2 (in fact "section 2 of chapter I" would be better). –  Mathieu Dubois Jul 15 '11 at 11:28
This sound similar to \autoref of hyperref. Have a look on its manual. –  Martin Scharrer Jul 15 '11 at 11:36
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