Ultimate Software, a provider of web-based payroll and workforce management solutions, said United Dominion Realty Trust has selected its Intersourcing on-demand delivery model. With more than 2,100 employees, United Dominion is the fourth-largest apartment real estate investment trust (REIT) in the U.S., owning and operating apartment communities nationwide. To manage its HR/payroll processes, the firm has been using a service bureau, but found that it needed more robust HR functionality and workforce reporting tools to streamline processes and manage its labor force as efficiently as possible. United Dominion selected Intersourcing last September.