This paper presents a service spectrum, which defines the prominent characteristics of services in the context of SOA paradigm. The service spectrum comprises service identification, aspects, attributes, metadata, messaging, and repository/management, serving as a foundation to a systematic service engineering discipline, in which the major stages of the service lifecycle are addressed - portfolio assessment, service analysis, service modeling, service realization, service assembly, and service management. This holistic disciplined approach covers the contents, categories, models, activities, artifacts, standards/policies, patterns, and tools to comprehensively incorporate the industry best practices and our past experience in the real-world SOA solution designs.