The Dachsprache reference article from the English Wikipedia on 24-Jul-2004
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Dachsprache

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Dachsprache means a language form that serves as standard language for different dialects, mostly in a dialect continuum, even though these dialects may be so different, that mutual intellegibility is not possible on the basilectal level between all dialects. In 1982 Romansch (by then called "Rumantsch Grischun" by most of its speakers) was successfully created by Heinrich Schmid as such a Dachsprache for a number of quite different Romance language forms spoken in parts of Switzerland. Standard German to some extent functions the same way.