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In the special case of a '''finitary relation''', for concreteness a '''''k''-place relation''', the concepts of figure and ground are defined as follows:
In the special case of a '''finitary relation''', for concreteness a '''''k''-place relation''', the concepts of figure and ground are defined as follows:
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:* The '''ground''' of ''L'' is a [[sequence]] of ''k'' [[nonempty]] [[set]]s, ''X''<sub>1</sub>, …, ''X''<sub>''k''</sub>, called the ''domains'' of the relation ''L''.
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:* The '''ground''' of ''L'' is a [[sequence]] of ''k'' [[nonempty]] [[set]]s, ''X''<sub>1</sub>, …, ''X''<sub>''k''</sub>, called the ''domains'' of the relation ''L''.
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:* The '''figure''' of ''L'' is a [[subset]] of the [[cartesian product]] taken over the domains of ''L'', that is, ''F''(''L'') ⊆ ''G''(''L'') = ''X''<sub>1</sub> × … × ''X''<sub>''k''</sub>.
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:* The '''figure''' of ''L'' is a [[subset]] of the [[cartesian product]] taken over the domains of ''L'', that is, ''F''(''L'') ⊆ ''G''(''L'') = ''X''<sub>1</sub> × … × ''X''<sub>''k''</sub>.
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Strictly speaking, then, the relation ''L'' consists of a couple of things, ''L'' = (''F''(''L''), ''G''(''L'')), but it is customary in loose speech to use the single name ''L'' in a systematically equivocal fashion, taking it to denote either the couple ''L'' = (''F''(''L''), ''G''(''L'')) or the figure ''F''(''L''). There is usually no confusion about this so long as the ground of the relation can be gathered from context.
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Strictly speaking, then, the relation ''L'' consists of a couple of things, ''L'' = (''F''(''L''), ''G''(''L'')), but it is customary in loose speech to use the single name ''L'' in a systematically equivocal fashion, taking it to denote either the couple ''L'' = (''F''(''L''), ''G''(''L'')) or the figure ''F''(''L''). There is usually no confusion about this so long as the ground of the relation can be gathered from context.
==Definition==
==Definition==