The Matrix[1] entity supports cross-source correlation and analysis. Its <Frame> element enumerates a set of Source entities that are to be analysed together.
<Matrix Key=’key’>
[ <Title> matrix-title </Title> ]
[ MAT_PROTO_SUBJ | MAT_COMMENTARY | MAT_DATE ] ...
[ TEXT_SEG ] ...
</Matrix>
<Frame>
SOURCE_LNK ...
[ TEXT_SEG ] ...
</Frame>
<ProtoPerson { DetKey=’key’ || Key=’key’ }>
[ <Title> proto-title </Title> ]
MAT_LINK ...
[ TEXT_SEG ] ...
</ProtoPerson>
<!-- or ProtoAnimal, ProtoPlace, ProtoGroup, ProtoEvent -->
<Commentary DetKey=’key’>
[ <Title> commentary-title </Title> ]
MAT_LINK ...
[ TEXT_SEG ] ...
</Commentary>
<ProtoDate DetKey=’key’>
[ <Title> date-title </Title> ]
MAT_LINK ...
[ TEXT_SEG ] ...
</ProtoDate>
<Link [Type=’link-type’] { DetLnk=’key’ || Value=’value’ }>
[ TEXT_SEG ] ...
</Link>
The Matrix entity is typically used to compare/contrast the profiled sources from a number of Source entities. This would usually be to solve a specific problem, or to study a given person or family, and contrasts with the Source entities themselves which are designed to assimilate one source each for any future study.
[1] "An environment or material in which something develops; a surrounding medium or structure", from Oxford Dictionaries Online (http://www.oxforddictionaries.com/definition/american_english/matrix : accessed 28 Oct 2015), s.v. “matrix”, alternative 1.