Digital television is a new, interesting, and rich platform for developing next generation multimedia services. Navigator is the most important service of digital television. It acts as the main index of all services available in set-top box. In this paper, we describe the definition of a Navigator, its functionality, its information retrieval processes, and its information source based on DVB-SI (Service Information) which is multiplexed in MPEG2 Transport Streams (TS). The process of developing a Navigator in Java language is presented. A software model including navigation model, state model of a remote control, and data structures is introduced. Furthermore, a software reference model for DVB-SI demultiplexing is described. Its implementation was based on a client/server approach using the User Datagram Protocol (UDP). The development issues, performance evaluation, and future research topics are given as conclusions.