Firstly, the original point of these prefixes was to provide a quick way of moving these files to the end of the parts.lst file.
With the formalisation of the header in 2008, some of this need has been superceded and tools should really query the LDRAW_ORG line to determine a file's category.
Files with a "_" description prefix are hard-coded colour versions of parts where we know the official LEGO part number for the part in that colour. These may be individually moulded parts (0 !LDRAW_ORG Part Physical_Colour ...) or assemblies of several moulded parts (0 !LDRAW_ORG Shortcut Physical_Colour ...).
Files may have a "~" description prefix, to move them out of the parts list for 4 reasons:
1) "Obsolete" files, errors or files that use patterning techniques that we no longer use. These also have the word "Obsolete" somewhere in the description.
2) "Moved to" file references, where we originally used an "unknown" (3-digit or uNNNN) part number and have since discovered the official number, or to maintain backward compatibility where a part has developed variants.
3) "Assembly component" files that represent an individually moulded part which is always issued by LEGO as part of an assembly and are therefore unlikely to be needed on its own, except by advanced users. Parts can be promoted out of this category if LEGO start to issue the part on its own, e.g. the 2x2 turntable plate base (3680).
4) "Flexible part component" files that ease the construction of flexed versions of the part
I would support a wholesale update to the LDRAW_ORG metadata lines for these files to separate and identify these categories and move away from the use of special characters to imply meaning.
With the formalisation of the header in 2008, some of this need has been superceded and tools should really query the LDRAW_ORG line to determine a file's category.
Files with a "_" description prefix are hard-coded colour versions of parts where we know the official LEGO part number for the part in that colour. These may be individually moulded parts (0 !LDRAW_ORG Part Physical_Colour ...) or assemblies of several moulded parts (0 !LDRAW_ORG Shortcut Physical_Colour ...).
Files may have a "~" description prefix, to move them out of the parts list for 4 reasons:
1) "Obsolete" files, errors or files that use patterning techniques that we no longer use. These also have the word "Obsolete" somewhere in the description.
2) "Moved to" file references, where we originally used an "unknown" (3-digit or uNNNN) part number and have since discovered the official number, or to maintain backward compatibility where a part has developed variants.
3) "Assembly component" files that represent an individually moulded part which is always issued by LEGO as part of an assembly and are therefore unlikely to be needed on its own, except by advanced users. Parts can be promoted out of this category if LEGO start to issue the part on its own, e.g. the 2x2 turntable plate base (3680).
4) "Flexible part component" files that ease the construction of flexed versions of the part
I would support a wholesale update to the LDRAW_ORG metadata lines for these files to separate and identify these categories and move away from the use of special characters to imply meaning.
Chris (LDraw Parts Library Admin)