The Define Drawing Information Block opcode doesn't perform any operation. It acts as a container for other drawing information opcodes. If used, this should be the first opcode in the file, following the DWF header.

Info Possible nested list of Drawing Information opcodes

There are a set of drawing information opcodes that a DWF reading application may want to inspect before actually rendering the .dwf file. For example, a user might want to search a directory of many .dwf files for those files created by a specific author. Because almost all opcodes are optional in a DWF, the reader can't assume that the Define Drawing Author opcode will be found in a file and, consequently, is forced to read and parse files in their entirety.

The Define Drawing Information Block opcode solves this problem by allowing all drawing information opcodes to be contained at the very beginning of the file. If, after reading the information block, the desired opcode is not found (the "drawing author" in this example), the DWF reader can safely assume that no occurrences can be found anywhere in the file.

If the Drawing Information Block opcode is used, by convention it should be the first opcode in the file (following the DWF header), and all other "Define Drawing xxx" opcodes should be contained therein.

Define Drawing Author, Define Drawing Initial View, Define Drawing Creator, Define Drawing Description, Define Drawing Creation Time, and Define Drawing Modification Time