1. A computing system comprising; a processor; a lexical data store having a plurality of lexical entries, each lexical entry having a segment field and a metadata field, the segment field identifying a textual string and the metadata field identifying one or more segment identifiers that are different than the textual string and are mapped to the textual string by the lexical entry; a rules data store having a plurality of rule entries, each rule entry representing a rule that indirectly identifies valid compound words by identifying, in the rule entry, at least one segment identifier and an operation to be performed on textual strings that are mapped to the at least one segment identifier in the lexical data store to form the valid compound words; and memory storing executable instructions, which, when executed by the processor, configure the computing system to: receive an input signal indicative of a textual input; access a rule entry in the rules data store representing a particular one of rules; parse the particular rule into a rule structure that represents the at least one segment identifier and the operation from the accessed rule entry; determine whether the textual input comprises a valid compound word, by applying the rule structure to the textual input to match the textual input to a textual string identified from the lexical data store based on the at least one segment identifier and the operation represented by the rule structure; and generate and electronically transmit, through a communication interface, an output indicative of the determination whether the textual input comprises a valid compound word.