1. A computer-implemented method comprising: receiving, at a computer device, a collection of text-based strings associated with a document; determining, via the computer device, a set of lexical identifiers for the collection of text-based strings, the set of lexical identifiers comprising one or more lexical identifiers assigned to uniquely represent one or more of the text-based strings of the collection, wherein the one or more lexical identifiers are assigned using a map, wherein, if wholly represented in the map, a text-based string of the collection is represented by a lexical identifier, and, if not wholly represented in the map, the text-based string of the collection is represented using multiple lexical identifiers from the map, wherein the map comprises lexical identifier values such that any text-based string can be represented using either a single lexical identifier or a new lexical identifier created using multiple lexical values of the map.