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    Combining context provisions with graph grammar rewriting rules - the three-dimensional case

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    In this paper we consider the representation and generation of three-dimensional structures by means of formal descriptive methods. Graph and graph grammar theory present us with a powerful two-dimensional representational method, and we propose to use these concepts as basis for the three-dimensional case. Three dimensional structures however, often appear in other structures and within a certain context. This context may be defined or influenced by the overall structure, or other related structures. We therefore need to be cognisant of the role that these contexts play when we introduce the concepts of three-dimensional graph and graph grammar systems, with particular reference to contextual rewriting rules. It is the combination of context provisions with graph grammar rewriting rules that results in a formal descriptive method which represents three-dimensional structures. The generative abilities of the concepts we introduce and discuss, are illustrated by considering the generation of various chemical structural formulae

    Going Beyond Counting First Authors in Author Co-citation Analysis

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    The present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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