@book{SWP-94-05,
year={1994},
author={Lunde, R{\"udiger}
    and Claus-Peter Wirth\protect\index{Wirth, Claus-Peter}},
title={{ASF$^+$ --- eine ASF-\"ahnliche Spezifikationssprache}},
publisher={{SEKI Publications}},
series={{SEKI-Working-Paper SWP--94--05 (ISSN 1860--5931)}},
address={Univ.\ Kaiserslautern},
note={\url{http://www.ags.uni-sb.de/~cp/p/swp9404}},
abstract={Maintaining the main aspects of the
algebraic specification language ASF as presented in {[Bergstra\&al.89]}
we have extend ASF with the following concepts:
While once exported names in ASF must stay visible up to the top the
module hierarchy,
ASF$^+$ 
permits
a more sophisticated hiding of signature names.
The erroneous merging of distinct structures that 
occurs when importing different actualizations of the same 
parameterized module in ASF
is avoided in ASF$^+$ by a more adequate form of
parameter binding.
The new ``Namensraum''-concept of ASF$^+$ 
permits the specifier on the one hand directly to
identify the origin of hidden names
and on the other 
to decide 
whether an imported
module is only to be accessed or whether 
an important property of it is to be modified.
In the first case he can access one single globally 
provided version; in the second he has to import a copy of the module.
Finally 
ASF$^+$ 
permits
semantic conditions on parameters and the 
specification of 
tasks for a theorem prover.},
}