So if the seals weren't necessarily stamps, then they don't necessarily have to include information about the contents of a jar or package being sent to a far away land. Which is really too bad for us—decipherment would somewhat easier if we know or could guess that the glyphs represent something that might be shipped in a jar (Harappans grew wheat, barley, and rice, among other things) or that part of the glyphs might be numbers or place names.
Since the seals aren't necessarily stamp seals, do the glyphs have to represent language at all? Well, the glyphs do recur. There's a fish-like glyph and a grid and a diamond shape and a u-shape thing with wings sometimes called a double-reed that are all found repeatedly in Indus scripts, whether on seals or on pottery sherds.
What Rao and his associates did was try to find out if the number and occurrence pattern of glyphs was repetitive, but not too repetitive. You see, language is structured, but not rigidly so. Some other cultures have glyphic representations that are considered not language, because they appear randomly, like the Vinč inscriptions of southeastern Europe. Others are rigidly patterned, like a Near Eastern pantheon list, with always the head god listed first, followed by the second in command, down to the least important. Not a sentence so much as a list.
So Rao, a computer scientist, looked at the way the various symbols are structured on the seals, to see if he could spot a non-random but recurring pattern.
Sources and Further Information
Rao, Rajesh P. N., et al. 2009 Entropic Evidence for Linguistic Structure in the Indus Script. Science Express 23 April 2009
Guide to the Indus Civilization
Bibliography of the Indus Civilization
Study of the Indus Script at Harappa.com.
