In communication theory, coding is to transform the original information symbols according to certain mathematical rules. The purpose of coding is to transmit information to the destination as quickly as possible under the condition of ensuring a certain quality. There are two problems to be solved in communication: one is how to transmit information with as few symbols as possible without distortion or allowing a certain degree of distortion, which is the source coding problem; Secondly, in the case of channel interference, how to increase the anti-jamming ability of signals and maximize the information transmission rate is a channel coding problem. The source coding theorem (Shennong's first theorem) gives the possibility to solve the former problem, and at the same time gives a coding method; The coding theorem of noisy channel (Shennong's second theorem) points out that there is such a coding, which can make the error probability of transmission close to the capacity of the channel, thus giving the possibility of solving the latter problem. Therefore, the use of coding in communication can minimize the influence of distortion and channel interference, and at the same time, information can be transmitted at an information transmission rate close to the channel capacity.

function

1. Authentication code is the unique identification of the classified object of authentication information.

2. Classification When the classified objects are classified according to certain attributes, a code is designed for each category.

Message coding

Message coding

In this case, the code can be used as an identifier to distinguish object categories. This sign needs a clear and definite structure.

3. Sorting Because all coded symbols have a certain order, it is more convenient to sort in this order.

4. Special meaning Due to certain needs, when some special symbols are used to represent specific things or concepts, coding provides certain special meanings, such as technical parameters and performance indicators of some classified objects.

purpose

The purpose of information coding is to establish the connection between the data in the computer and the information actually processed, and improve the efficiency of information processing.

fundamental principle

The basic principle of information coding is to meet the requirements of users and processing logically;

The structure is easy to understand and master;

It should be widely applicable and easy to expand.

Code type

Generally, there are two types of codes, one is meaningful code, that is, it gives the code a certain practical meaning and is easy to classify; One kind is meaningless code, which only gives the information element a unique code to facilitate the operation of information. Commonly used code types are:

(1) sequence code, that is, the sequential coding of information elements;

(2) interval code, that is, a code interval represents a certain information group;

(3) Memory codes, that is, codes that can help associative memory.

There are many forms of information, so there are many coding schemes. For example, the graphic character codes (GB 5007-85) including the first and second classes of Chinese characters and common symbols, the "Big Five" of other characters and symbols such as Japanese and Korean, and the "american standard code for information interchange Code" of English characters were all formulated in China.

system design

1. Determine the system objectives: determine the information content of PDM system according to the overall system objectives, and conduct a comprehensive investigation on the data and information related to enterprise products; Analyze the nature and characteristics of all kinds of information; Optimize and reorganize information classification; Unify the definition of information name and provide system design data. It mainly includes the following information: data, design documents (scheme, calculation, etc. ), process documents (process route, process card, etc. ), product drawings, change orders, etc.

2. Data investigation and analysis:

Preliminary investigation: A preliminary investigation is to investigate the basic situation of an enterprise, including its production plan, production type, product variety, output, equipment, technology, production capacity, quality, cost, product stability, product development trend, inventory, sales and service, etc.

Status Survey: According to the information scope determined by the preliminary survey, conduct an in-depth investigation on the existing information classification, coding and product structure data of the enterprise, and collect all expired documents, statements, account details and various documents.

message coding

message coding

Feature analysis: analyze the collected information through the feature table, and define things or concepts, data items and data elements that need unified names.

3. Determine the list: preliminarily sort out the collected information, list the list or list, and describe it with words and figures as much as possible.

4. Formulating coding rules Every message must have an independent code, and the information code is generally a composite code composed of classification code and identification code. Classification code is the code indicating the information category, and the identification code is the code indicating the information features (such as structure shape, material, technology, etc.). ).

The structure of information classification coding system generally adopts decimal classification system. In the decimal classification system, the hierarchical structure is represented in the form of a tree, and the position of each code point number depends on the previous one, which is represented by numbers from 0 to 9, and each code point represents a fixed meaning.

In order to ensure the correct input of codes, check codes should be added to long codes and key codes to check the errors caused by their input and transmission operations.

Different types of information can have different coding rules, and the same type of information can be coded with the same length.

5. Establishment of coding system: Select the coding system that has matured in practical application, and try to use the existing information coding (material coding, product coding, tooling coding, etc.). ) has different contents in the enterprise, and tries, adjusts and modifies it to make it an information coding system of the enterprise.

6. Verification: After the coding system is formed, it should be tested, modified and supplemented to ensure the reliability and applicability of the coding system.

7. Release and implementation: All classification systems, coding systems and codes shall conform to enterprise standards.

8. Conclusion

Product information coding is the basic work for discrete manufacturing enterprises to implement informatization. It is the premise of implementing PDM and the necessary condition of implementing ERP. For group enterprises, if their subsidiaries are related to business, both single-site companies and multi-site companies should adopt a unified coding system. Scientific coding system design is the key to ensure the success of PDM/ERP. When designing the coding system, standardization personnel, product designers, purchasing personnel, production managers, etc. should participate, fully consider the needs of each independent subsystem, and at the same time consider the integration of coding of each subsystem to avoid creating new system islands.