# Reference Models for Digital Manufacturing Platforms
## 3 Reference Models Alignment
### Smart Manufacturing Ecosystem  
The Advanced Manufacturing Series (AMS) of standards by NIST provide different specifications for Smart Manufacturing Systems (SMS), and they are described below. In addition to the specifications in the AMS series, the National Institute of Standards and Technology [38] describes the standard landscape for SMSs. The document contains a detailed description of the characteristics and enabling technologies of SMS, and a comprehensive list of standards and standardization activities relevant for SMS, from three different perspectives (Figure 3):  
* Product Lifecycle Management (Product): Includes six phases for the product development lifecycle (design, process planning, production engineering, manufacturing, use and service, end-of-life, and recycling). This perspective is equivalent to the RAMI 4.0 Life Cycle and Value stream dimension. Figure 2: I4.0 Communication protocol stack. * Production System Lifecycle (Production): Defines five phases in the lifecycle of production equipment: design, build, commission, operation and maintenance, and decommission and recycling. This perspective is also equivalent to the RAMI 4.0 Life Cycle & Value Chain, from the point of view of the manufacturing equipment provider. * Business Cycle for Supply Chain Management (Business): This perspective regards the plan-source-make-deliver-return phases of the Supply-Chain Operations Reference model (SCOR). This perspective can also be mapped to the Life Cycle and Value stream of the RAMI 4.0 model in collaborative use cases. Alignment to RAMI 4.0  
Regarding the AMS Series, Part 1-Reference Architecture for Smart Manufacturing [39] provides a modelling framework for specifying the architecture of both collaborative production systems and the software systems that supports them. The Reference Architecture for Smart Manufacturing Part 1 contains functional models to identify production activities-from product design to production-and descriptions of information flows between them. The different activities depict the life-cycle of products and can be aligned to the IEC 62890 product life-cycle model Instance Production phase described above. Distribution, maintenance and dispatching are out of the scope of the reference architecture, and product design is not expanded in the document, so the entire reference model can be regarded as a detailed description of the activities and data workflows within the instance production phase. NIST Software Requirements Specification to Distribute Manufacturing Data [22] defines general functional and non-functional requirements for the distribution of manufacturing data across an enterprise. The document covers Volatile Data Streams (VDS) and Query-able Data Repository (QDR) applications for internal and external data access to manufacturing data. VDS applications are based on the MTConnect HTTP protocol [40], whereas QDR applications should use an HTTPS client-server REST-compliant communication and therefore, there are significant differences between AMS-2 and the 14.0 connectivity whitepaper. NIST Guide to Industrial Wireless Systems Deployments [41] aims to provide a framework for integrated manufacturing design and analysis. The objective is to facilitate the integration and exchange of information between the product design and the product manufacturing phases, focusing on big data analytics and (deep) machine learning algorithms rooted in cloud services. The framework  
Figure 3: Smart Manufacturing Ecosystem Perspectives. defines a four-layer model which can be mapped to the RAMI 4.0 layers. The framework consists of the following layers:  
* Manufacturing System Layer: Represents the physical system and can be mapped to the RAMI 4.0 asset layer. * Model Ecosystem Layer: This layer contains the modelling environment and runtime for the digital models of the manufacturing layer. It can be mapped to the RAMI 4.0 Integration layer, Communication layer and to some extent to the Information layer.