Introduction In the 21st century, enterprises face increasingly fierce international competition. To win markets and customers, they must strengthen management through the implementation of MRPII/ERP. However, upper-level production planning management is increasingly influenced by the market, and it is evident that plans are failing to keep pace with changes. Faced with demanding customer requirements for delivery dates, more product modifications, and constant order adjustments, enterprise decision-makers realize that planning must rely on the market and actual operational status, rather than solely on material and inventory returns to control production. Furthermore, MRPII/ERP software primarily targets resource planning. These systems can typically handle events from yesterday (historical analysis) and predict and handle events tomorrow, but often leave gaps in the handling of events happening today. Traditional production site management is essentially a black box operation, which can no longer meet the needs of today's complex and ever-changing competition. Therefore, how to make this black box operation transparent, identify any issues affecting product quality and cost, improve the real-time nature and flexibility of planning, and simultaneously improve production line efficiency has become a major concern for every enterprise. Manufacturing Execution System (MES) can precisely fill this gap. MES (Manufacturing Execution System) is the execution layer between the planning layer and the shop floor operation control system (SFC), primarily responsible for production management and scheduling. It enhances manufacturing competitiveness by controlling all factory resources, including materials, equipment, personnel, process instructions, and facilities, providing a systematic way to integrate functions such as quality control, document management, and production scheduling on a unified platform. This enables a real-time ERP/MES/SFC system for the enterprise. MES is a new concept proposed by the American management community in the 1990s. The Advanced Manufacturing Research (AMR) institution in the United States, through surveys of numerous enterprises, found that existing enterprise production management systems generally consist of enterprise management software represented by ERP/MRPII, production process monitoring software represented by SCADA and HMI (Human Machine Interface), and a suite of MES software to automate operations and support comprehensive enterprise integration. Because MES emphasizes control and coordination, modern manufacturing information systems not only have excellent planning systems but also execution systems that ensure plans are implemented effectively. Therefore, MES has been rapidly adopted by enterprises abroad, bringing significant economic benefits. Enterprises recognize that only by extracting data from the product level, passing through the operational control level, and delivering it to the management level, achieving full enterprise information integration through continuous information flow, can they remain competitive in an increasingly fierce market. As enterprise production models gradually shift towards agile manufacturing, the implementation of Business Process Reengineering (BPR), the heterogeneity of enterprise environments, and the formation of dynamic alliances between enterprises place even higher demands on MES (Manufacturing Execution System). Traditional MES solutions are ill-suited to the requirements of agile manufacturing. An MES solution for agile manufacturing must not only be cost-effective but also possess excellent adaptability, reconfigurability, and integrability. Therefore, many organizations and research institutions abroad have begun researching MES solutions for agile manufacturing. I. Typical MES Models 1. MES Connotation The demand for MES arose from the transformation of production models over the past decade, thus its development history is shorter than that of MIS, MRP, and CAD/CAM. However, research and application of MES have progressed very rapidly. MESA International (MES International Federation) is a trade federation dedicated to promoting MES concepts and products. To help its member organizations promote MES in the business world, it has developed a series of research, analysis, and development plans. The MES International Federation defines MES as: MES can optimize and manage the entire production process from order placement to product completion through information transmission. When real-time events occur in the factory, MES can react promptly, report, and guide and process them using current, accurate data. This rapid response to changes in status allows MES to reduce non-value-added activities within the enterprise, effectively guiding the factory's production operations, thereby improving the factory's on-time delivery capability, material flow performance, and production return rate. MES also provides mission-critical information about product behavior within the enterprise and throughout the entire product supply chain through two-way direct communication. As can be seen from the above definition, the key to MES is emphasizing the optimization of the entire production process. It requires collecting a large amount of real-time data during production and processing real-time events promptly. Simultaneously, it maintains bidirectional communication capabilities with the planning and control layers, receiving relevant data from both layers and feeding back processing results and production instructions. Therefore, MES differs from traditional shop floor controllers, which primarily focus on production management through work orders and auxiliary material flow, and also from unit controllers, which emphasize job and equipment scheduling. Instead, MES should be considered as a production model, integrating the planning and scheduling, tracking, monitoring and control, material flow, quality management, equipment control, and Computer Integrated Manufacturing Interface (CIM) of the manufacturing system to ultimately implement a manufacturing automation strategy. The figure illustrates the data flow diagram and position of MES in enterprise production management. 2. MES Framework Model In the late 1980s, with the rapid development of computer and network technologies, interdisciplinary integration and crossover emerged in process industry control. Simultaneously, the combination of signal processing, computer, communication, and computer network technologies with automatic control technologies enabled process control to break through the isolated automation model, giving rise to a new integrated automation model that combines control, optimization, scheduling, management, and operation. In the 1990s, with the rapid advancements in computer technology, research on computer-integrated production systems became a cutting-edge topic in the field of automation. Large international process industry enterprises, especially petrochemical companies, highly valued the application of information integration technology, investing significant enthusiasm and effort in building factory-level, company-level, and even super-company-level information integration systems. These systems use data-oriented (rather than application-oriented) models as their core, connecting real-time and relational databases to monitor, control, and diagnose production processes, monitor the environment, integrate units, simulate, and optimize. At the management decision-making level, they handle material balancing, production planning, scheduling, production scheduling, enterprise resource planning, and offline/online simulation and optimization. According to foreign statistics, the main control and optimization technologies adopted by petrochemical enterprises to improve economic efficiency include: advanced control technology for equipment, inventory management, automated laboratory management, optimization of public works, and optimization of production scheduling. Among these, the economic benefits of production scheduling optimization are the most significant. This solves the information problems with both production and management characteristics that were previously difficult to handle in integrated automation systems for process industries. Currently, this has become the mainstream framework for the theory and products of integrated automation systems for process industries in advanced Western industrial countries. 3. MES Positioning Model As a manufacturing-oriented system, MES inevitably has close relationships with other production management systems within the enterprise. MES acts as an information hub, essentially a communication tool providing real-time data from the production site to other application systems. The positioning model of MES is shown in the figure. It can be seen that there is functional overlap between MES and other subsystems. For example, MES, CRM, and ERP all include human resource management; MES and PDM both have document control functions; and MES and SCM both include scheduling management, etc. The extent of overlap between systems depends on the actual implementation in the factory, but the value of each system is unique. 4. MES Functional Model MES itself is a collection of various production management functional software. MESA has summarized eleven main MES functional modules through the practice of its members, including: detailed process scheduling, resource allocation and status management, production unit allocation, process management, human resource management, maintenance management, quality management, document control, product tracking and product list management, performance analysis and data acquisition. Actual products may contain one or more of these functional modules. The functions of each module are briefly described below: (1) Detailed Process Scheduling: Optimizes shop floor performance through job sequencing and scheduling based on limited resource capabilities. (2) Resource Allocation and Status Management: Guides workers, machines, tools, and materials on how to coordinate production and tracks their current working status and recent completion status. (3) Production Unit Allocation: Sends materials or processing orders to a processing unit to begin the operation of a process or step through production instructions. (4) Document Control: Manages and distributes information related to products, process specifications, designs, or work orders, while also collecting standard information related to work and the environment. (5) Product tracking and product list management: By monitoring the position and status of workpieces at any time, the historical records of each product are obtained, which provide users with traceability of product groups and the usage of each final product. (6) Performance analysis: The results measured in the actual manufacturing process are compared with past historical records, enterprise-set goals, and customer requirements. The output reports or online displays are used to assist in performance improvement. (7) Human resource management: Provides employee status information data (working hours, attendance, etc.) updated in minutes, and guides personnel work based on changes in personnel qualifications, work patterns, and business needs. (8) Maintenance management: Ensures the normal operation of machines and other assets and equipment through activity monitoring and guidance to achieve the factory's execution goals. (9) Process management: Guides the factory's workflow based on plans and actual product manufacturing activities. The functions of this module can also be implemented by production unit allocation and quality management. Here it is implemented as a separate system. (10) Quality management: Records, tracks, and analyzes the quality of products and processing processes in real time according to engineering goals to ensure product quality control and identify issues that need attention in production. (11) Data Acquisition: Monitor, collect, and organize data from personnel, machines, and underlying control operations, as well as process and material information. This data can be manually entered in the workshop or acquired through various automated methods. II. Current Status and Suggestions for the Application and Development of MES 1. Current Status of MES Development As a product of the transformation of production mode, MES mostly originated from the internal needs of factories. Traditional MES (T-MES) developed from sporadic workshop-level applications in the 1970s. After accumulating considerable experience, some professional companies engaged in MES development gradually emerged, and their systems have developed fairly mature standards. Usually, they develop relatively standardized MES for specific production types or specific functional requirements, and have a certain market share. Although MES was proposed after MRPⅡ/ERP, it is located in the execution layer between the control layer and the planning layer. Under the control of the planning layer, it collects real-time data related to production from the underlying control system and performs short-term production operation planning, scheduling, monitoring, resource allocation, and production process optimization. To build a more advanced planning layer system on the basis of the existing MES system, it is necessary to first understand the current status of MES system construction. MES systems are mainly divided into two categories: dedicated MES systems and integrated MES systems. If the existing system is a dedicated system, it is developed for a specific domain of problems, such as shop floor maintenance, production monitoring, limited capacity scheduling, or SCADA. Its system reconfigurability is weak, making it difficult to dynamically modify and configure functions in response to changes in business processes. When further implementing advanced enterprise information systems, the overall system integration should be considered. Ideally, it should be developed in-house or customized, fully considering the structure and functions of the original MES system and seamlessly integrating the new system with the existing one. If the existing system is an integrated MES system, it has good integration capabilities, customization, reconfigurability, scalability, and interoperability. It can easily achieve integration between different vendors, protection of the original system, and plug-and-play (P&P) functionality. Enterprises can choose a suitable software system from mature, highly scalable suites. While evaluating the existing MES system, it is also necessary to consider whether the new planning layer system requires improvements to the existing MES system and whether the existing system can meet the needs of the new system's construction. For example, ERP systems require data from MES regarding production operations, such as the number of periodic inventory checks, production capacity, material consumption, labor and production line performance, work-in-process (WIP) storage location and status, and actual order execution. SCM systems need to retrieve the actual status of production orders, the company's current actual production capacity, and the interrelationships of production shift changes from MES. CRM systems require successful quotations and on-time delivery from the MES system, which provides real-time production data at every moment. Can the existing MES system provide this data and meet these needs? If not, the MES system itself must be improved first. 2. Several Suggestions for MES After clarifying the company's needs and understanding the current state of the existing MES system, whether developing a software system tailored to the company's needs or adopting a ready-made software package, the following issues must be considered: 1. Pay attention to the characteristics of the process manufacturing industry. Most MRPII/ERP systems on the market today evolved from discrete manufacturing and are more suitable for discrete manufacturing. When developing your own software or using packaged software, pay attention to the characteristics of process enterprises. For example, production planning mainly relies on market forecasting, cost accounting mainly uses parallel carry-over methods, and work scheduling is done only on a per-production-line basis. 2. Emphasize the implementation of MES system projects. Currently, most state-owned enterprises use so-called MES or SFCS systems, which are merely software that partially reflects the actual factory manufacturing execution system, not standard MES system software. The entry barrier for MES systems is relatively high; it's considered low only because it's not a true MES system. MES systems should be implemented on a project-by-project basis because domestic enterprises often have incorrect understandings and attitudes towards management software (expecting every action performed by the software to be reversible or canceled, failing to standardize workflows, or allowing for arbitrary changes). 3. Emphasize system integration to avoid information silos. From the perspective of the AMR three-tier enterprise integration model, the planning layer system needs to be closely integrated with the MES system to realize its full potential. A planning layer system detached from MES lacks the support of underlying data, and its results are unreliable. To ensure that the MES system and the planning layer system use a unified and standardized data format and access method, the MES system must not only provide data sources for the planning layer system, but the planning layer's plans must also control the MES system. For example, ERP's planning data is the basis for MES to schedule production; SCM controls the formulation of production plans and the production time of certain parts in the factory through the procurement and supply time of external materials; the specific customer requirements in CRM's purchase orders are an important basis for guiding factory production; PDM provides MES with actual production process documents and various formulas and operating parameters. 4. Pay attention to the different focuses of the same modules. In the management system that the enterprise is about to implement, some functional modules may already exist in the MES system. For example, both MES and ERP have human resource management modules; both MES and PDM have document control functions; both MES and SCM have scheduling management, etc. What should be done when such functional overlap occurs? In fact, the focus of the same type of module in different systems is different. For example, in the human resource management module, the MES system mainly records the workers' work situation, while the human resource module in ERP focuses on the management of various information of each employee, including personal information, salary, etc. 5. It's crucial to ensure seamless integration between MES and ERP systems. This is primarily because most IT companies implementing management information systems in my country's manufacturing sector don't collaborate with industrial control companies developing MES systems. Many ERP vendors understand that without interfaces, production line management is impossible, meaning ERP will always be a crude, inefficient management approach. Therefore, ERP vendors need to provide interfaces for MES data uploads, while MES vendors are responsible for uploading the data and integrating and managing it according to the interfaces provided by the ERP system. 6. Emphasize the accumulation of phased results. Enterprise IT investment can easily reach millions, tens of millions, or even hundreds of millions of yuan. To ensure a return on such a large investment, it's essential to focus on phased results. This requires companies to identify the right entry point, plan holistically, and implement the entire project in phases. Furthermore, it's vital to summarize the phased results of the MES system to lay a solid foundation for better future applications. III. Development Trends of MES 1. Two Trends in the MES Software Development and Application Market MES software developers and MES system integrators are facing pressure from two sides: top-down penetration by ERP software developers and system integrators, extending their functions to MES; and bottom-up impact from HMI and SCADA software developers and system integrators, increasing the functionality of MES. Strong automation system suppliers (such as Siemens and Rockwell Automation) are acquiring successful MES companies or developing MES software packages to seize market share. Currently, MES software products are not suitable for all industries. 2. Benefits and Trends of MES MES is a production management technology and real-time information system oriented towards the shop floor level. It is a fundamental technical means to implement enterprise agile manufacturing strategies and achieve agile shop floor production. Because MES emphasizes control and coordination, modern manufacturing information systems not only have excellent planning systems but also execution systems that ensure plans are implemented effectively. Therefore, in just a few years, MES has been rapidly adopted by enterprises abroad, bringing significant economic benefits. Chinese enterprises have been implementing enterprise management software, mainly MRPII/ERP, for nearly 20 years. There are a large number of ERP vendors and development teams in the industry, but only a small portion of these vendors will develop towards MES. The reason is that MES is closely integrated with industrial control, and its research and implementation require a strong foundation in industrial automation and experience in industrial field engineering. This is a relatively high technical threshold, excluding many ERP-type IT vendors. However, with the development of the industry and the scale of the economy, a considerable number of IT vendors will merge or cooperate closely with automation vendors and manufacturing enterprises. In 2-3 years, MES vendors may emerge like mushrooms after rain, and their technology and implementation methods will inevitably become more mature. IV. Conclusion (1) MES plays a crucial role in the entire enterprise information integration system, serving as a bridge between production and management activities. Without implementing MES, integrated management and control is just empty talk. For ERP systems targeting manufacturing and process industries, without MES, it will be impossible to organize, manage, and optimize production according to market demands. (2) MES technology has matured significantly over the past decade. However, the development and application of MES is a process, not an event. It is unimaginable that a successful MES implementation can be achieved overnight. To achieve long-term success, it is necessary to transform the manufacturing environment, obtain organized support, and make adaptive changes to the management mechanism. At the same time, MES software also needs further development and improvement in terms of maintenance and interface with other IT management software. (3) To make the investment in enterprise information technology network return quickly, starting with MES is a wise choice. However, the implementation of MES requires proper planning and detailed analysis. It can start with solving one or two urgent factory production bottleneck problems and gradually expand. (4) In the past, MES was usually a large monolithic software system with high customization and maintenance costs. With the development of computer support technology, it has become possible to develop more modular and flexible MES systems, and the cost of implementing and maintaining MES has been greatly reduced. Therefore, as the core of process CIMS, MES has good application prospects in the comprehensive automation process of process industries such as petroleum, chemical, pharmaceutical and pulp and paper. Manufacturing Execution System (MES) software bridges the gap between the enterprise planning level and the production shop process control system, serving as a link for the integration of manufacturing process information. MES helps enterprises implement complete closed-loop production by emphasizing the overall optimization of the manufacturing process, while also providing a solid foundation for the implementation of agile manufacturing. A deep understanding of this advanced management concept and a grasp of its development trends are of significant theoretical and practical value for the proper research and promotion of MES applications in my country.