1. A method for mapping one or more key-value pairs associated with a document into one or more tabular structures, the one or more key-value pairs each having a key name and a value, and each of the one or more tabular structures having one or more rows and columns for storing the values, the method comprising: reading the document, by a document reader, to identify the one or more key-value pairs associated with the input document; determining whether a value associated with a given one of the one or more key-value pairs is a scalar value or a composite value; in the event that the value associated with the key-value pair is a scalar value: extracting the key name of the key-value pair, storing the value of the key-value pair in a row of the tabular structure, or in the event that the value associated with the key-value pair is a composite value: extracting the key name of the key-value pair; generating a sub-tabular structure associated with the extracted key name of the key-value pair.