Each element in an IGDS file may have one or more attribute linkages attached to it. The IGDS reader and writer support both user data and database attribute linkages.
Note, however, that the DGN V8 reader and writer do not support the interpretation1 of user linkages.
Database linkages and MSLINKS are supported. FRAMME linkages are supported for reading.
Because an element may have more than one linkage, linkages are stored in an FME feature attribute list named igds_linkage{#}. As with other feature attribute lists, # starts at zero and increments for each successive linkage.
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The term interpretation in this case refers to the reader extraction of format information into human-readable and semantically valuable information on a feature. FME will read the linkages, but not in a way which clarifies what the data is for, or what it represents. It reads values and types, such as number = 1234, rather than interpreting the values as something like a river length, or a mountain elevation. In addition, data may be binary, rather than strings or numbers. Linkages are read in this way, and the writer is limited to consuming the basic format that the reader creates, rather than creating the correct interpretation of arbitrary schema attributes as linkages. |