To realize all the functions of EDI, the following four conditions need to be met, including EDI communication standard and EDI semantic grammar standard.
Data communication network is the technical basis to realize EDI.
In order to transmit files, it is necessary to have a wide coverage, efficient and safe data communication network as its technical support environment. Because EDI transmits commercially or administratively valuable documents in standard format, communication network must have a series of security functions such as format verification, confirmation, tracking, tamper prevention, theft prevention, electronic signature, file filing and so on, in addition to general data transmission and exchange functions. , and can provide legal evidence when there is a legal dispute between users.
The message processing system MHS provides the most ideal communication environment for EDI. In order to realize EDI in MHS, ITU-T put forward the communication standard X.435 of EDI in 1990 according to the requirements of international standard EDIFACT, making EDI a service of MHS communication platform.
Computer application is the internal condition to realize EDI.
EDI not only transmits standard data files through computer network, but also requires automatic identification and processing of accepted and sent files. Therefore, users of EDI must have a perfect computer processing system.
From the perspective of EDI, a user's computer system can be divided into two parts: one part is an EDI subsystem closely related to EDI, including message processing, communication interface and other functions; The other part is the internal computer information processing system, commonly called EDP (Electronic Data Processing).
The better the EDP of an enterprise, the higher the efficiency of using EDI. Similarly, only after extensive use of EDI can we give full play to the role of EDP within each unit. Therefore, only by combining EDI and EDP comprehensively and effectively can the greatest economic benefits be obtained.
Standardization is the key to realize EDI.
EDI is to realize the intercommunication and automatic processing of business documents and documents, which is different from the interactive processing of man-machine dialogue, but the automatic response and automatic processing between computers. Therefore, the standardization of file structure, format and grammar rules is the key to realize EDI.
The development of EDI's international standards is as mentioned above, that is, the UN/EDIFACT standard has become the mainstream of EDI standards. However, international standards alone are not enough. In order to adapt to the domestic situation, countries need to formulate their own EDI standards. Therefore, it is a very heavy and complicated work to realize EDI standardization. At the same time, after adopting EDI, some official seals and paper documents will be cancelled, and the management mode will change from planned management to process management. All these will lead to a series of social changes, so people call EDI "a structural business revolution".
EDI legislation is a social environment to ensure the smooth operation of EDI.
The use of EDI will inevitably lead to changes in the way of trade and administration, as well as a series of legal issues. For example, the legal effect of electronic documents and electronic signatures, legal evidence and arbitration in case of disputes. Therefore, in order to fully implement EDI, relevant laws and regulations must be formulated. Only in this way can we create a good social environment and legal guarantee for the full use of EDI.
However, making laws is often a long process. How to deal with legal disputes before the official promulgation of EDI law? The general practice of advanced developed countries abroad is that before using EDI, all the trading partners of EDI sign an agreement to ensure the use of EDI. Such as the American Bar Association's "EDI Agreement for Trading Partners".
Implementation process of EDI
Functional model and working principle of EDI system
In EDI, the information objects exchanged by EDI participants are called postal parcels. In the exchange process, if all the information obtained by the receiver from the sender is contained in the exchanged package, it is considered to be semantically complete, and the package is called a complete semantic unit (CSU). The producers and consumers of CSU are collectively called the end users of EDI.
In the process of EDI, the messages exchanged are all structured data, and the whole process is completed by EDI system. The structure of EDI system is shown in Figure 2. 1.
User interface module
Business managers can use this module for input, query, statistics, interruption, printing and so on. Keep abreast of market changes and adjust strategies.
Internal interface module
This is the interface between EDI system and other internal information systems and company databases. After the EDI system processes the external EDI messages, most related contents need to be sent to other information systems through the internal interface module, or other information systems can be queried to confirm and reply to other EDI messages.
Message generation and processing module
This module has two functions:
A. receive commands and information from user interface module and internal interface module, generate various EDI messages and documents such as orders and invoices according to EDI standards, and send them to other EDI users through EDI network by communication module after being processed by format conversion module.
B. automatically process messages sent by other EDI systems. In the process of processing, it is necessary to contact the information system of this unit to obtain the necessary information and reply to other EDI systems, and at the same time send the relevant information to other information systems of this unit.
If the requirements of the other party cannot be met due to special circumstances and cannot be properly resolved through repeated consultations between the EDI systems of both parties, such incidents will be submitted to the user interface module for manual intervention and decision-making.
Format conversion module
All EDI documents must be converted into standard exchange format, and the conversion process includes syntax compression, nesting, code replacement and necessary EDI syntax control characters. In the process of format conversion, grammar check should be carried out, EDI messages with grammatical errors should be rejected, and the other party should be notified to resend.
communication module
This module is the interface between EDI system and EDI communication network. Including calling, automatic forwarding, legality and integrity check, error alarm, automatic response, communication recording, message assembly and disassembly and other functions.
In addition to these basic modules, EDI system must have some basic functions.
A. Naming and addressing functions
The end user of EDI must be the only identifiable name enjoyed by * * *. Naming and addressing functions include communication and authentication.
In communication, EDI uses addresses instead of names to communicate. Therefore, it is necessary to provide a method of addressing by name, which should be based on the open system directory service ISO9594 (corresponding to ITU-T X.500). In authentication, there are several levels of necessary authentication, namely, communication entity authentication, mutual authentication between sender and receiver, etc.
B. Safety function
The security function of EDI should be included in all the above modules. It includes the following contents:
Mutual authentication between end users and all EDI participants;
Data integrity;
Electronic (digital) signatures between EDI participants;
Deny the possibility of EDI operation activities;
Key management.
C. Semantic data management function
A complete semantic unit consists of multiple information units. The management service functions of CSU and IU include:
IU should be identifiable and distinguishable;
IU must support reliable global reference.
It should be able to access the contents indicating IU attributes, such as syntax, structural semantics, character set and encoding;
Should be able to track and locate IU;
Provide convenient and consistent access for end users.
Operation flow of EDI
Nowadays, the universal EDI communication network is a mailbox system based on MHS data communication platform, and its communication mechanism is the storage and forwarding of information between mailboxes. The specific implementation method is to attach a large-capacity information processing computer to the data communication network and establish a mailbox system on the computer. Both parties need to apply for their own mailbox, and the communication process is to send the documents to the other party's mailbox. The file exchange is completed automatically by the computer. When sending files, users only need to enter their own mailbox system.
EDI can be regarded as a sub-platform of MHS communication. Figures 2.2, 2.3 and 2. Explain the position and function of EDI in the seven-layer protocol of computer communication network, the communication and exchange principle of EDI mailbox system and the complete communication flow respectively.
Each functional module in the communication process is described as follows:
Mapping)-Generate EDI flat files.
EDI flat file is a standard intermediate file, which maps user's application files (such as documents and bills) or data in the database through the application system. This process is called mapping.
Flat files are documents and bill files that users can edit, modify and operate directly through the application system. It can be read, displayed and printed directly.
Translation-generate EDI standard format files.
Its function is to generate EDI standard format files from flat files through translation software.
The EDI standard format file is the so-called EDI electronic document, or electronic bill. It is the basis of trade and business communication between EDI users. EDI standard format file is an ASCII file that only computers can read. According to the requirements of EDI standard, it generates an ASCII code file containing control symbols, codes and document information by adding specific separators, control symbols and other information to the directory items in the document file (flat file).
connect
This step is completed by computer communication software. Users access EDI mailbox system through communication network and deliver EDI electronic documents to the other mailbox.
The EDI mailbox system automatically completes the delivery and delivery, and according to the requirements of X.400 (or X.435) communication protocol, auxiliary information such as envelope, letterhead, letter tail, delivery address and security requirements are added to the electronic document.
Receiving and processing of electronic data interchange files
The receiving and processing process is the opposite of the sending process. First of all, the receiving user needs to access the EDI mailbox system through the communication network, open his mailbox, receive the letter to his computer, and restore it to an application file after format verification, translation and mapping. Finally, edit, process and reply the application documents.
In the actual operation process, the EDI application software package provided by EDI system includes all functions such as application system, mapping, translation, format verification, communication connection and so on. Its processing process, users can be regarded as a "black box", there is no need to care about the specific process inside.
Fig. 2.5 is a schematic diagram of a trading company's customs declaration through EDI communication network.
Communication service of EDI
The EDI communication environment (EDIME) consists of an EDI communication system (EDIMS) and multiple EDI users (ediimg), as shown in figure 2.6. The development and application of EDI is realized through computer communication network, mainly in the following three ways.
Point to point (PTP) mode
Peer-to-peer mode refers to EDI's information transmission and terminal processing through the communication network according to the agreed format, so as to complete business communication with each other. This method is generally used in early EDI communication, but it has many shortcomings. For example, when EDI users have dozens or even hundreds of trading partners instead of a few, this method is time-consuming and requires repeated transmission. At the same time, this communication mode is synchronous and not suitable for transnational and cross-industry applications.
In recent years, with the development of technology, this peer-to-peer approach is still useful in some fields, but it will be improved. The new method adopts the peer-to-peer structure of remote decentralized control, and uses the remote information service terminal based on terminal open network system to convert data into EDI messages through specific applications, thus realizing international EDI message interoperability.
value added network
It is those VADS companies that use existing computers and communication network equipment to complete general communication tasks and increase the service functions of EDI. The services provided by VADS company to EDI users are mainly mailbox rental and protocol conversion, which are transparent to users. The introduction of mailbox realizes the asynchronism of EDI communication, improves efficiency and reduces communication cost. In addition, the transmission of EDI messages in VADS company's own system (that is, in VAN) is asynchronous, that is, store and forward.
Although the VAN method has many advantages, due to the different EDI service functions of each value-added network, the VAN system cannot be interoperable, thus limiting the global application across regions and industries. At the same time, this method also has a fatal disadvantage, that is, VAN only realizes the lower layer of the computer network, which is equivalent to the lower three layers of the OSI reference model. However, EDI communication often occurs between the application processes of various computers, which determines that the relationship between EDI application processes and VAN is quite loose and inefficient.
MHS mode
Information processing system MHS is a functional model of international e-mail service system jointly proposed by ISO and ITU-T. It is based on the network platform of OSI open system, adapts to all kinds of information, and is fast, accurate, safe and reliable through network connection. It is a non-real-time electronic communication system based on store and forward, which is very suitable for EDI transmission system. MHS creates a perfect application software platform for EDI, which reduces the technical difficulty and workload of EDI design and development. ITU-T X.435/F.435 specifies the EDI information processing system and communication services, and takes EDI and MHS as the official services of OSI application layer. EDI is interconnected with MHS, so that EDI messages can be directly put into the email address of MHS, and the perfect transmission of EDI messages can be realized by using the address function and message transmission service function of MHS.
The EDI information processing system consists of information transfer agent (MTA), EDI user agent (EDI-UA), EDI information storage (EDI-MS) and access unit (AU), as shown in Figure 2.7. The MTA completes the establishment, storage/forwarding of the connection, and the MTS system is composed of multiple MTAs. The transmission process of EDI in MHS is shown in Figure 2.8.
The memory of EDI-MS is located between EDI-UA and MTA, and it is like a resource * * * or mailbox, which helps EDI-UA to send, transfer, store and retrieve EDI information. At the same time, EDI-MS converts the messages received by EDI UA into EDI message database, and provides functions such as database query and retrieval. In order to facilitate retrieval, EDI-MS maps the envelope, header and text of the message to different feature fields of MS information entities, and provides services such as automatic forwarding and automatic echo.
EDI-UA is the interface between electronic file system and transmission system. Its task is to use the function of MTS to transmit electronic documents. EDI-UA divides the information objects it processes into two types: one is called EDI message (EDIM) and the other is called EDI receipt (EDIN). The former is to transmit electronic documents, and the latter is to report the receiving results. EDI-UA and MTS*** are isomorphic to form EDI information system (EDI-MS), and EDI-MS and EDI users together form EDI communication environment (EDIME).
The combination of EDI and MHS has greatly promoted the development of international EDI business. In order to realize the global communication of EDI, the EDI communication system also adopts the X.500 series directory system (DS).
DS can provide the functions of adding, deleting and modifying directories such as the supplement of global EDI communication network and the increase of users, so as to obtain comprehensive information of a series of attributes such as name and address network service, communication capacity list and number inquiry. The combination of EDI, MHS and DS has achieved a new leap in information exchange and provided a broad prospect for the development of EDI. The integrated network of EDI, HS and DS is shown in Figure 2.9.
/EDI spec/EDI kwg/EDI 10 . PHP