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TDF 4.1 SPECIFICATION
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=====================
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The file def_4_1.db gives a compact machine readable description of the
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encoding of TDF version 4.1, generated directly from the TDF specification.
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The similar description for version 4.0, def_4_0.db, is also given.
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The make_tdf tool may be used to generate code from these descriptions
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and a template file; alternatively other tools may be written to process
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the description.
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The information given consists of:
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- the list of basic sorts [sorts],
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- the list of list sorts [lists],
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- the list of simple list sorts [slists],
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- the list of optional sorts [options],
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- the list of linkable sorts [linkable_entities],
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- the list of unit sorts [kinds_of_unit],
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- the list of edge constructs for linkable sorts [graph_edges],
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- the major version number [major_version],
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- the minor version number [minor_version].
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Each sort has the following associated information:
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- the sort name [sortid],
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- the number of bits used to encode the sort [encoding_bits],
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- whether extended encoding is used [has_extension],
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- the list of constructs of that sort [constructs].
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Each construct has the following associated information:
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- the construct name [construct_name],
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- the encoding of the construct [encoding],
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- the name of the construct result sort [result_sort],
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- the list of construct parameters [parameter_sorts],
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it may also have:
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- a list of boundary alignment information [boundaries],
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- a list of parameter break information [break].
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Each construct parameter has the following associated information:
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- the parameter name,
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- the name of the parameter sort.
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The boundary alignment information gives a list of numbers which indicate
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that the nth argument should be aligned on a byte boundary. The parameter
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break information is also a list of numbers which indicate that the value
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of the construct needs to be partially evaluated after the nth argument
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has been read.
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Each list or simple list entry consists of a sort name with a '_list'
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suffix. Similarly each optional sort entry consists of a sort name
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with an '_option' suffix.
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Each linkable sort has the following associated information:
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- the sort name [entity_sort],
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- the name used to identify the sort in a TDF capsule [entity_identifier].
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Each unit sort has the following associated information:
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- the sort name [unit_elements],
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- the name used to identify the sort in a TDF capsule [unit_identifier].
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Each edge construct has the following associated information:
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- the result sort name [edge_sort],
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- the construct name [edge_construct].
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For a formal grammar of the description file, see the sid grammar,
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syntax.sid, in the make_tdf source.
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