2. The system of claim 1 , wherein the dictionary-constructing mechanism to generate the dictionary from the first textual data comprises generating a plurality of keys of the dictionary, from second textual data, each key associated with an identifier, the keys comprising: a plurality of static word or phrase keys, each static word or phrase key listing one or more unchanging words in a particular order; and, a plurality of dynamic phrase keys, each dynamic phrase key listing a plurality of words and one or more placeholders in a particular order, each placeholder denoting a place where a word or phrase other than the words of the dynamic phrase key is to be inserted; and, the plurality of keys, including the identifiers of the keys are stored on the storage device.
2. The system of claim 1 , wherein the dictionary-constructing mechanism to generate the dictionary from the first textual data comprises generating a plurality of keys of the dictionary, from second textual data, each key associated with an identifier, the keys comprising: a plurality of static word or phrase keys, each static word or phrase key listing one or more unchanging words in a particular order; and, a plurality of dynamic phrase keys, each dynamic phrase key listing a plurality of words and one or more placeholders in a particular order, each placeholder denoting a place where a word or phrase other than the words of the dynamic phrase key is to be inserted; and, the plurality of keys, including the identifiers of the keys are stored on the storage device. 5. The system of claim 2 , wherein the second textual data is the first textual data to be compressed using the constructed dictionary.