<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>0034-7426</journal-id>
<journal-title><![CDATA[Revista Colombiana de Matemáticas]]></journal-title>
<abbrev-journal-title><![CDATA[Rev.colomb.mat.]]></abbrev-journal-title>
<issn>0034-7426</issn>
<publisher>
<publisher-name><![CDATA[Universidad Nacional de Colombia y Sociedad Colombiana de Matemáticas]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S0034-74262019000200205</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[Existential Graphs on nonplanar surfaces]]></article-title>
<article-title xml:lang="es"><![CDATA[Gráficos existenciales sobre superficies no planas]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[OOSTRA]]></surname>
<given-names><![CDATA[ARNOLD]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad del Tolima Facultad de Ciencias ]]></institution>
<addr-line><![CDATA[Ibagué ]]></addr-line>
<country>Colombia</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2019</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2019</year>
</pub-date>
<volume>53</volume>
<numero>2</numero>
<fpage>205</fpage>
<lpage>219</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_arttext&amp;pid=S0034-74262019000200205&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_abstract&amp;pid=S0034-74262019000200205&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://www.scielo.org.co/scielo.php?script=sci_pdf&amp;pid=S0034-74262019000200205&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT. Existential graphs on the plane constitute a two-dimensional representation of classical logic, in which a Jordan curve stands for the negation of its inside. In this paper we propose a program to develop existential Alpha graphs, which correspond to propositional logic, on various surfaces. The geometry of each manifold determines the possible Jordan curves on it, leading to diverse interpretations of negation. This may open a way for appointing a "natural" logic to any surface.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN. Los gráficos existenciales sobre el plano constituyen una representación bidimensional de la lógica clásica, en la cual una curva de Jordan indica la négation de su interior. En este artículo se propone un programa para desarrollar los gráficos existenciales Alfa, que corresponden a la lógica preposicional, sobre diferentes superficies. La geometría de cada variedad determina las posibles curvas de Jordan sobre ella, lo cual conduce a interpretaciones diversas de la negación. Esto puede abrir el camino para asignar una lógica "natural" a cualquier superficie.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Existential graphs]]></kwd>
<kwd lng="en"><![CDATA[2-dimensional topological manifolds]]></kwd>
<kwd lng="en"><![CDATA[Jordan's Curve Theorem]]></kwd>
<kwd lng="es"><![CDATA[Gráficos existenciales]]></kwd>
<kwd lng="es"><![CDATA[2-variedades topolágicas]]></kwd>
<kwd lng="es"><![CDATA[teorema de la curva de Jordan]]></kwd>
</kwd-group>
</article-meta>
</front><back>
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