OPTN: Volume & Open Interest = Liquidity ?

[Dave Lord <zdave@xxxxxxxxx>]

I am looking for opinions about Volume and Open Interest as indicators of options liquidity.  Do they, together or separately, provide an indication of the degree of liquidity?  If so, at what levels -- or at what ratio to each other?  Is this the same for buying *and* writing options?  If not, how do they differ?

Thanks in advance for your thoughts, Dave
zdave@xxxxxxxxx