1. A method in a computer system for managing employee data for an enterprise, comprising: providing, by a Human Capital Management (HCM) computer system, a hierarchical employment data model comprising three tiers of data records, the three tiers of data records comprising: a top relationship tier comprising one or more relationship data records for each employee of a plurality of employees of a first enterprise, each of the one or more relationship data records storing work relationship information defining a relationship between one employee of the plurality of employees and the first enterprise, a middle terms tier below the top relationship tier comprising one or more terms data records, each of the one or more terms data records storing employment terms information for one of the one or more relationship data records of the top relationship tier, and a bottom assignment tier below the middle terms tier comprising one or more assignment data records, each of the one or more assignment data records storing assignment information for one of the one or more terms data records in the middle terms tier, wherein defining the hierarchical employment data model for the first enterprise comprises defining a set of fields for employee data records of the first enterprise at each of the top relationship tier, the middle terms tier, and the bottom assignment tier of the hierarchical employment data model; receiving, by the HCM computer system, a plurality of employee data, each employee data of the plurality of employee data describing one of the plurality of employees of the first enterprise; for each employee data of the plurality of employee data: determining, from the employee data, each relationship that an employee described by the employee data has with the first enterprise, each set of terms for each relationship of the employee, and each set of assignments for each set of terms for the employee by: parsing, by the HCM computer system, the employee data into one or more portions of the employee data, and for each portion of the one or more portions of the employee data: identifying, by the HCM computer system, a data type of the portion of the employee data, determining, by the HCM computer system, an associated tier for the portion of the employee data based on the data type of the portion of the employee data, the associated tier being one of the top relationship tier, the middle terms tier, and the bottom assignment tier, and storing, by the HCM computer system, the portion of the employee data in the associated tier in a data repository configured according to the hierarchical employment data mode; receiving, by the HCM computer system, a request for information about a first employee of the plurality of employees; parsing, by the HCM computer system, the request into one or more request portions; for each request portion of the one or more request portions: identifying, by the HCM computer system, a request data type of the request portion, determining, by the HCM computer system, an associated request tier for the request portion based on the request data type, the associated request tier being one of the top relationship tier, the middle terms tier, and the bottom assignment tier, and retrieving, by the HCM computer system, response employee data from the associated request tier of the data repository; composing, by the HCM computer system, a response message comprising the retrieved response employee data for each request portion; and transmitting, by the HCM computer system, the response message in response to the request.