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u |
tree
structure
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one
to one and one to many relationships
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objects
grouped in container
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express
relationship directly
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implicit
acess path to the data
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multiple
relationships
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links
of specific semantics
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u |
occurance
operator
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allow
various instances
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matching
one DTD
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useful
for subclassing
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u |
Inheritance
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by
reference
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by
position
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