Matthias P. Krieger

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We prove optimal lower bounds for multilinear circuits and for monotone circuits with bounded depth. These lower bounds state that, in order to compute certain functions, these circuits need exactly as many OR gates as the respective DNFs. The proofs exploit a property of the functions that is based solely on prime implicant structure. Due to this feature,(More)
Automated test data generation is an important method for the verification and validation of UML/OCL specifications. In this paper, we present an extension of DNF-based test case generation methods to class models and recursive query operations on them. A key feature of our approach is an implicit representation of object graphs avoiding a representation(More)
Operation contracts consisting of pre- and postconditions are a well-known means of specifying operations. In this paper we deal with the problem of operation contract simulation, i.e., determining operation results satisfying the postconditions based on input data supplied by the user; simulating operation contracts is an important technique for(More)
Executing formal operation contracts is an important technique for requirements validation and rapid prototyping. Current approaches require additional guidance from the user or exhibit poor performance for underspecified contracts that describe the operation results non-constructively. We present an efficient and fully automatic approach to executing OCL(More)
From its beginnings, OCL is based on a strict semantics for undefinedness, with the exception of the logical connectives of type Boolean that constitute a three-valued propositional logic. Recent versions of the OCL standard added a second exception element, which, similar to the null references in object-oriented programming languages, is given a(More)
We explore the potential of adding objective functions to OCL operation contracts. If an operation contract includes an objective function, the operation has the obligation to yield results that make the objective function assume an optimal value. Thus, an objective function expresses a preference among the possible operation results that conform to the(More)
The utilization of 2-(2-nitrophenyl)propyloxycarbonyl (NPPOC) as a photolabile primary amine cage enables the thiol-Michael 'click' reaction to be photo-triggered. The photolabile amine exhibits efficient catalytic activity upon UV irradiation and is shown to initiate the photopolymerization of tetrathiol and diacrylate comonomers via Michael addition.