Some file formats are good for long-term storage of files, because they’re likely to be usable for a long time. (“A long time” in computer terms means ten or twenty years; if you want files that really last, get a rock, a hammer, and a chisel.) These are preservation formats. There are also file formats which are good for moving files from one application to another. These are interchange formats. (See my last post, “Tied to an Application”, on why these are important.) The two have a lot of overlap but aren’t the same.

The two have things in common. Specifications should be publicly available. The format should represent the information without losing any. There shouldn’t be legal barriers to implementation.

The big difference is that interchange formats have to work right now. A format which is otherwise great doesn’t help most users if they can’t import it into a new application with available software. Interchange formats have to keep editing-related information. PDF is a great format for preservation, but try turning a PDF into an editable file. The results are usually disastrous if the file’s at all complex.

Is Microsoft Word a usable interchange format? Much as it makes me gag, I have to say yes in many cases. You can open Word files with quite a number of different applications. Someone got paid a lot to reverse-engineer the Word format, but the job has been done. A safer bet, though, might be to export from Word to ODF. The current version can do this natively, and the ODF Add-In on SourceForge claims to do it better. That way, whatever application is importing the file is following a published spec, leaving less room for bugs and other surprises.

RTF (Rich Text Format) is nominally an interchange format, but it’s actually a poor one. Its handling of character encoding is miserable and can result in garbled files when an application guesses wrong about a file’s encoding. It isn’t standardized.

Don’t count on any interchange format to give you exactly the same content with a new application. There will almost always be subtle difference in formatting from one application to another. Color profiles may be treated differently. Metadata might not be 100% preserved.

Don’t use JPEG for image interchange. Its lossy compression means there will be spillage along the way. TIFF is good for getting images from one application to another.

When you export a file, keep it in the original format as well, at least till you’re sure you’ve exported it to your satisfaction. If anything goes wrong, that leaves you a chance of exporting again with better tools or settings, or if all else fails of manually moving information over.