# On the Design and Implementation of a Blockchain-Based Data Management System for ETO Manufacturing
## 3 Blockchain network layer (BNL)
### Metadata of Each Production Entity  
As described in the first section, the production process of an ETO-type manufacturing enterprise mainly involves multiple entities, such as supervision, marketing, product design, production, and quality inspection. The production department will have two production lines: discrete semi-finished product processing lines and flow-type finished product assembly lines. Each entity in the BPDMS generates its process data and uploads it to the ledger of the corresponding channel.  
Production is an orderly process from sales orders to qualified finished products. Therefore, each entity maintains an ordered relationship between the preceding and following entities by the relevant key fields in the metadata, as shown in Figure 3.  
* **Marketing department entity (sales department)** is mainly responsible for customer needs and obtaining contract orders with customers, which mainly include contract ID, contract name, customer information, and ordered products and quantities.
* **The product design entity** designs the product according to the requirements of the product ordered in the contract, and generates the production drawing and process route of the product, including the product ID, drawing ID, drawing file, product process route, and contract ID. Here, the contract ID is the data field associated with the preceding entity.
* **The production management entity** is an important unit of the production process, and converts product orders into production work orders. The main data fields here include production work order ID, production schedule, planned completion time, product ID, contract ID, and drawing ID. It should be noted that due to the different types of production lines, the types of work orders are also different, and can be divided into work orders for processing lines and work orders for assembly lines.  
Figure 3: Metadata of each entity and its data flow.  
* **A discrete processing line** is a semi-finished product process, which mainly produces product components. Since the production processes of different components are different, it is necessary to record the production data of the components and determine in a timely manner whether the production is carried out according to the process route. The on-chain data of this production line entity include component ID, work-order ID, line ID, worker list, product ID, processing routing, and routing execution signature.
* **An assembly line** is a streamlined operation that produces a final product by assembling related components. The on-chain data of this entity mainly comprise work-order ID, component ID list, work list, assembly process description, product ID, and production completion time. The supervisor can track and trace the production process of the product by calling the query smart contract, where the product ID is the key field.
* **The quality inspection entity** is an important step in production, which mainly checks whether the product meets the specifications and requirements according to the product characteristics. The data on the chain include product ID, quality inspector, quality inspection time, and result.