Industry 4.0 represents a significant transformation in the manufacturing industry, driven by a wide range of technologies, viz. Cyber-physical systems (CPS), aiming to enhance efficiency, productivity, and global competitiveness. CPS enables the co-engineered interaction of networks consisting of physical and computational components through data sharing. Data is the most critical factor influencing all four performance outcomes, namely operational, product, economic, and responsiveness. Systematic data alignment into knowledge graph is achieved through ontology. Therefore, ontology is essential in Industry 4.0 as it enables self-assessment, knowledge sharing, and context representation. The objective is to design an ontology-based asset maintenance framework in a Cyber-physical production systems (CPPS) capable of defining and designing maintenance plan for the specified asset. It proposes a conceptualization of CPPS for maintenance where maintenance domain ontologies are utilized to define maintenance agents capable of generating maintenance plan for the given asset. The significance of this work lies in facilitating collaboration and communication across heterogeneous platforms, thereby enabling real-time computation for smart diagnostics and maintenance in CPPS which is based on maintenance domain ontologies.