This thesis presents an information model developed to represent, organize, and link information essential to maintenance and operation management, a facility management function. It first describes the facility management domain and identifies facility information as a primary element to sustain the decision-making process. Then it discusses the need for open communication channels to allow information exchange throughout facility's life-cycle phases, reviews several models addressing information integration, and introduces a framework, which ensures interoperability within different facility management functions. The proposed information model focuses on the information describing building mechanical systems and utilizes object-oriented modeling language. To validate the information model, a prototype is implemented and a real case-study is investigated to provide data and to demonstrate how the research relates to practice.