Facility Management Software Systems (FMSS) represent an advanced integration of technology into the operational aspect of buildings and other related facilities. These software systems are built to streamline processes, create efficiencies, centralize information, and thereby facilitate the effective and efficient management of facilities.

The conceptual underpinning of FMSS is primarily drawn from the fields of information technology and computer science. The design principles of these systems are influenced by various theories such as the Information Processing Theory and the Systems Theory. Information Processing Theory provides the basis for developing FMSS that can gather, process, store, and disseminate information effectively and efficiently. Systems Theory, on the other hand, influences the development of an FMSS that is integrated, interactive, and interdependent, facilitating the synchronized functioning of various components of a facility.

The architecture of FMSS is typically based on the concept of a database management system, a key product of the evolution of data science. This system acts as a repository of information pertaining to the various facets of facility management, ranging from asset tracking and maintenance scheduling, to space allocation and energy management. The sophisticated nature of FMSS leverages the power of algorithms - a sequence of computational procedures - to process information and generate actionable insights for decision-making.

FMSS employ a range of advanced technologies to carry out their functions. Internet of Things (IoT) has been pivotal in transforming the landscape of facility management by enabling the development of smart buildings. IoT allows for the integration of various devices and systems within a facility, enabling them to communicate with each other and with the FMSS. This integration facilitates real-time monitoring and control of facilities. The use of Artificial Intelligence (AI) and Machine Learning (ML) in FMSS enhances their predictive capabilities, enabling them to anticipate and respond to potential issues before they escalate.

However, the adoption of these advanced technologies is not without its trade-offs. While AI and ML can enhance the predictive capabilities of FMSS, they also introduce complexity and potential vulnerabilities into the system, raising concerns around data privacy and security. Similarly, while IoT enables the seamless integration of devices and systems within a facility, it also increases the potential for cyber threats, given the increased number of access points into the system.

Despite these challenges, the benefits offered by FMSS are generally considered to far outweigh the potential downsides. The capacity of these systems to centralize data, automate processes, and generate timely and accurate insights can significantly enhance the operational efficiency and cost-effectiveness of facilities. It enables managers to make informed decisions, anticipate problems, and respond swiftly and competently when issues arise.

In conclusion, Facility Management Software Systems represent the confluence of advanced technologies and sophisticated system design, providing an integrated solution for the effective and efficient management of facilities. While the adoption of these systems presents certain challenges, their potential to transform the operational landscape of facilities makes them an indispensable tool in modern facility management. Therefore, understanding the workings of these systems is essential for any facility manager aiming to harness the power of technology to enhance their facility's performance and, ultimately, their bottom line.