Service design methodology has been incorporating methods and tools from multiple disciplines such as ethnography, management, system design and interaction design. Service design tools can be divided into three categories: basic research tools, service analysis tools, and in-depth guidance tools. Although user experience considered to be a key concern of service design, there is a lack of methods to describe profound user experiences and reveal deep meanings to the user. This paper introduces Semiotics Approach for Product Architecture Design (SAPAD) that provides a framework for representing meanings of service activities by adopting Stamper's semiotic ladder model. The semiotic ladder model is composed of six levels: 1) Physical level, 2) Syntactic Level, 3) Empiric Level, 4) Semantic Level, 5) Pragmatic Level, and 6) Social Level. This framework enables thorough exploration of the deep meanings, value and potential contradictions of stakeholders in complex interactive relationships between many system constituents. Through the two case studies of service design for: a) a blood donation vehicle service system, and b) a community elderly rehabilitation service system, SAPAD framework was proved to be very useful and effective for analyzing system inquiry data and synthesizing comprehensive interpretation levels of user experience with clear meaning relevance. Especially representing and understanding profound experience can form a basis for effective integration of trans-disciplinary perspectives critical for achieving integrity and sustainability of service system quality.