TAG1_PART1, TAG1_PART2, TAG1_PARTX (as well as TAG2_PART1, TAG2_PART2, TAG2_PARTX) are alternatives to TAG1 and TAG2 that allow you to split a tag name into two pieces and, for example, position one piece above the other on the symbol. You can create drawings with a mix of both symbols having split tags and other symbols carrying just the single TAG1 or TAG2 attribute.
Note: If a parent symbol has the single TAG1 attribute, related child symbols can have split tag attributes and vice versa. If a parent symbol has split tag attributes, related child symbols do NOT have to have split tag attributes. The default value character string of the symbol for the tag should be annotated as a default value on the TAG1_PART1 attribute definition.