The continuous series are Thomson Financial’s options calculated series available on the Datastream product. Unlike individual options series, continuous series do not expire until the actual options class ceases to exist. So these series have the most history, consider them like a basket off individual options. The values from the nearest expiry month options are used to calculate for example the Implied Volatility.
Please note: some datatypes in the options Data Category in Datastream are only available for the continuous series – behind the name of the datatype you’ll see “(Cont Series)”. This means these datatypes are not available for indiviudal options series.
You can find more background material in the ExtraNet of Datastream Navigator – in the Options User Companion.