# Reference Models for Digital Manufacturing Platforms
## 3 Reference Models Alignment
### Reference Model for Industrie 4.0 (RAMI 4.0)
#### 3.1.2 Life Cycle and Value Stream  
The second axis in the RAMI 4.0 reference model represents the life cycle of products and systems and is taken from the IEC 62890 standard [32]. The product life-cycle model first introduces a differentiation between product type and product instance. A product type is characterized by a unique product identifier, all the documentation associated with the product (development documents, manufacturing and test descriptions, technical documentation, etc.), and the required certificates. This definition of product type is valid for either hardware and software products, or software or hardware parts of products that bundle both hardware and software. A product instance, on the other hand, is an individual instantiation of a product type. A product instance is characterized by a unique instance identifier, such as a serial number or ordering number.  
From this fundamental differentiation between type and instance, the product life-cycle is divided into phases that detail the life cycle of both product type and product instance. Hence, all activities that concern the development, maintenance, and service of a product type, refer to the product type. In a similar fashion, all activities regarding the production, maintenance, and servicing of a specific product instance refer to the product instance.  
In the context of RAMI 4.0, the generic life-cycle model of a product type starts with the development phase, in which the product type is developed and tested in the targeted system environment. The development phase includes activities, such as product type design, sales ramp-up, testing, or piloting, and ends with the delivery release of the product type, when the product is released for sale. The operational businesses of the product type finishes with the end of product sales, typically when the product is to be obsoleted. During the product sales (and typically for an extended period thereafter), the product type is under the maintenance phase, where configuration management and after-sales support activities take place. Configuration management comprises all activities related to the management of the different versions and revisions of the product type. Depending on the service level agreements, one or several versions of the product type will have independent after-sales support phases. The sum of these phases is called the product life-cycle, where the term cycle refers to the fact that there is a recurring sequence of the different phases in the context of a particular product type.  
The product instance generic life time model starts with the production phase when the instancing of the product type begins. After the product instance is sold, the product instance enters the use phase, which starts with the product commissioning, installation, or activation, and ends with the decommissioning, de-installation or with an irreparable defect. Each product instance has a life time that comprises the production and use phases, i.e. starts with production and ends with the start of disassembling or disposal of the instance. The product life time is independent and can be significantly longer than the life-cycle of the product type.