Specifications define systems. The definition of a system can be stated casually or formally. A formal specification is a mathematically precise definition of software functionality. Informal specifications are less precise definitions of software functionality. The benefits of formal specifications are clear. Arguments against the use of formal specifications have been refuted;Several formal specification techniques are available for specifying imperative programs, e.g., Z, VDM, and SPECS. Most specification techniques for distributed/concurrent systems concentrate on low level issues, e.g., deadlock and synchronization;Structured Analysis (SA) specifications are a popular informal specification technique, but they lack a rigorous mathematical semantics. SA specifications are based on a graphical syntax with little underlying formal structure. In this thesis, we identify and formalize those underlying structures that are represented informally, provide a formal definition of a SA specification, develop formal interpretations for those components of SA specifications that are subject to varying interpretation, and define an operational semantics for animating SA specifications. The resulting formalized SA specifications are mathematically precise and can be used to specify distributed/concurrent systems.