Index: trunk/Ohana/src/libohana/doc/dvo-structures.txt
===================================================================
--- trunk/Ohana/src/libohana/doc/dvo-structures.txt	(revision 3466)
+++ trunk/Ohana/src/libohana/doc/dvo-structures.txt	(revision 4832)
@@ -36,2 +36,21 @@
    (can be loaded with translation, losing the exptime,
    and limited the number of Naverage to 0xffffff - in load_catalog) */
+
+------
+
+the DVO structure Catalog contains the data from a single sky patch, including:
+    average, measure, missing, and secfilt.  
+
+the catalog may be saved in one of 4 modes (catalog.catmode):
+    raw   : the old Elixir style which is a header + 4 binary tables
+    mef   : catalog is a single file with header and 4 fits tables
+    split : catalog is 5 files, one with the header and one for each table
+    mysql : catalog is 4 (or 5?) mysql tables
+
+    in split mode, the filename is the file of the descriptive header
+    and the averages, the measure, missing, and secfilt data are
+    stored in additional files referenced in the header and named
+    based on the filename (replacing extension .cpa with .cpb, .cpc,
+    .cpd, for example)
+
+