Roland N. Bol

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Nonmonotonic grew out attempts to the essential of common-sense It resulted a number important formalisms, most known them being circumsctiption method McCarthy [loll, default theory Reiter [136], autoepistemic Zogic Moore 11041. a systematic of these see the published Marek Truszczyfiski [98].) of the features of programming is it can support nonmonotonic(More)
We present a general theory for the use of negative premises in the rules of Transition System Specifications (TSSs). We formulate a criterion that should be satisfied by a TSS in order to be meaningful, that is, to unequivocally define a transition relation. We also provide powerful techniques for proving that a TSS satisfies this criterion, meanwhile(More)
The growing awareness that plants might use a variety of nitrogen (N) forms, both organic and inorganic, has raised questions about the role of resource partitioning in plant communities. It has been proposed that coexisting plant species might be able to partition a limited N pool, thereby avoiding competition for resources, through the uptake of different(More)
In this study, we assessed whether a range of temperate grassland species showed preferential uptake for different chemical forms of N, including inorganic N and a range of amino acids that commonly occur in temperate grassland soil. Preferential uptake of dual-labelled (13C and 15N) glycine, serine, arginine and phenylalanine, as compared to inorganic N,(More)
To understand the role of dung-derived carbon in the carbon cycle of grazed temperate grasslands, we need a procedure to trace dung-derived C. The natural C tracer technique of applying C4 dung to a C3 grass pasture allowed us to succesfully quantify the fate of cattle dung in the soil environment. Dung was collected from beef steers fed on either maize(More)
Bol, R.N., K.R. Apt and J.W. Klop, An analysis of loop checking mechanisms for logic programs, Theoretical Computer Science 86 (1991) 35-79. We systematically study loop checking mechanisms for logic programs by considering their soundness, completeness, relative strength and related concepts. We introduce a natural concept of a simple loop check and prove(More)
D In the framework of Lloyd and Shepherdson [16], partial deduction involves the creation of SLDNF-trees for a given program and some goals up to certain halting points. This paper identifies the relation between halting criteria for partial deduction and loop checking (as formalized in [l]). For simplicity, we consider only positive programs and(More)
When glaciers retreat they expose barren substrates that become colonized by organisms, beginning the process of primary succession. Recent studies reveal that heterotrophic microbial communities occur in newly exposed glacial substrates before autotrophic succession begins. This raises questions about how heterotrophic microbial communities function in the(More)