The user may define subclasses of this class.
The Product subclass provides means of identifying the data and assisting update procedures.
identity: supplies descriptive information about a set of data, including a product name and number, as well as a version number.
cycle: if the product is revised on a regular cycle, the length of the cycle is specified.
nextVersion: if the next release or version of the product is known, it can be provided here.
price: basic price information may be provided.
remarks: comments may also be given.