Visualization of CHR through Source-to-Source Transformation

In this paper, we propose an extension of Constraint Handling Rules (CHR) with different visualization features. One feature is to visualize the execution of rules applied on a list of constraints. The second feature is to represent some of the CHR constraints as objects and visualize the effect of CHR rules on them. To avoid changing the compiler, our implementation is based on source-to-source transformation

CHR^vis: Syntax and Semantics

The work in the paper presents an animation extension (CHR^{vis}) to Constraint Handling Rules (CHR). Visualizations have always helped programmers understand data and debug programs. A picture is worth a thousand words. It can help identify where a problem is or show how something works. It can even illustrate a relation that was not clear otherwise. CHR^{vis} aims at embedding animation and visualization features into CHR programs. It thus enables users, while executing programs, to have such executions animated. The paper aims at providing the operational semantics for CHR^{vis}. The correctness of CHR^{vis} programs is also discussed

Neighbor predation linked to natural competence fosters the transfer of large genomic regions in Vibrio cholerae

Natural competence for transformation is a primary mode of horizontal gene transfer. Competent bacteria are able to absorb free DNA from their surroundings and exchange this DNA against pieces of their own genome when sufficiently homologous. However, the prevalence of non-degraded DNA with sufficient coding capacity is not well understood. In this context, we previously showed that naturally competent Vibrio cholerae use their type VI secretion system (T6SS) to actively acquire DNA from non-kin neighbors. Here, we explored the conditions of the DNA released through T6SS-mediated killing versus passive cell lysis and the extent of the transfers that occur due to these conditions. We show that competent V. cholerae acquire DNA fragments with a length exceeding 150 kbp in a T6SS-dependent manner. Collectively, our data support the notion that the environmental lifestyle of V. cholerae fosters the exchange of genetic material with sufficient coding capacity to significantly accelerate bacterial evolution