There’s a file format — a structure for saving data — that is as powerful a tool in the writing world as a U.S. passport is in world travel. It’s known by the acronym OPML, and those letters should become as familiar to you as QWERTY. I”m going to post several blog entries on OPML; first is an introduction to the meaning and power of this format in practical and conceptual terms. Stay tuned and whether you know OPML or no, comment!