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2. 1 introduction

Product data management (Produc t Data Management _ PDM) takes the product as the center, integrates and manages all the product-related information and processes in the enterprise production process through computer network and database technology, so as to keep the product data consistent, up-to-date and safe in its life cycle. Provide an environment for engineers and technicians to work together Thus shorten the product research and development cycle, reduce costs, improve quality, and win competitive advantage for enterprises.

PDM system provides information management of product life cycle (including market demand research, product development, product design, sales, after-sales service), and can establish a parallel collaborative environment for product design and manufacturing within the enterprise. It can promote enterprises to improve their product quality, shorten the development cycle, improve work efficiency, accelerate the speed of products on the market, so as to improve the competitiveness of products. Therefore, PDM technology has been widely used in domestic and foreign manufacturing enterprises in recent years. The purpose of PDM is to transmit the right information, in the right form, to the right person at the right time and to complete the right task.

The actual demand of enterprises promotes the development of PDM products, and there are many mature products in the market, such as Metaph ase of S DRC Company, IMAN of EDS and so on. The early PDM products focus on the data management and sharing of departmental design links. With the improvement of user requirements and the development of technology, the enterprise-level PDM system that runs through the whole process of the enterprise has become a hot spot of development. This system can follow certain specifications, fully integrate the existing application systems, and also achieve information integration for the product data of cross-regional enterprises.

2. 2 distributed PDM system framework based on C, S mode

2. 2. 1c times computing structure model

The C / S computing structure mode can be defined as the working mode in which the client-side and server-side applications are developed separately and based on specific communication protocols to communicate with the server-side applications in order to cooperate to complete the corresponding tasks in the In t e rnet environment. The introduction of client / server system has injected new vitality into many desktop systems, reducing the memory burden of clients at the same time. Improve efficiency. In the aspect of network database, the request issued by the client is transmitted to the database server through the network, and the server interprets the query request, takes the data from one or more databases, and then queries it, thus reducing the network traffic. At present, the computing mode based on C / S has been widely used in the mechanical manufacturing industry, and CIMS engineering is a good example.

Cl ient/S erver is a city-separated computing model. Compared with the traditional host-based structure, it has better scalability and better performance-to-price ratio. The traditional Cl ient/S erver structure is mostly based on the two-tier structure of "fat client": client and server, and all clients implement their own user interface and application logic. the main problem of this structure is that the scalability of the system is poor and it is difficult to install and maintain.

With the continuous expansion of the system, due to the ever-changing requirements of the end customer, the client may be overwhelmed, and the oversize of the client program obviously runs counter to the idea of distributed computing. The solution to the above problems is to adopt the multi-tier Cl ient/S erver daily structure. At present, it is usually planned into three layers: client, application server and DBM S server. The logical structure is shown in figure 2. 1

Figure 2-1 Multi-layer Cramp S logic structure

1. Client

The client must install a special program that matches the server-side program. By executing client applications, based on specific network communication protocols such as T C P / IP. Realize the communication and interaction with the application server in order to complete the corresponding tasks.

2. Application server layer

The application server layer consists of a series of application servers, such as w eb server, middleware server that supports C ORBA, D C OM, Age nt, mobile Age nt and other middleware. By building the corresponding server, the communication and information transmission between the application server and the database application can be realized.

3. Database server layer

The database server layer consists of a series of commercial databases such as Oracle, S QL S erv er, Syba se, etc., and the corresponding database connection management drivers and other document information such as e-mail, Lo tu s Notes and so on.

2. 2. 2 the overall framework of PDM based on Cramp S mode

The internal structure of PDM is a hierarchical structure based on operating system, network environment and distributed database. The object management framework of PDM system is the core module of PDM system and the concrete embodiment of the information modeling idea of the whole PDM system. All entities involved in PDM, people, data, processes and relationships among entities are ultimately managed by the object management framework in the form of objects. The object management framework provides the cornerstone of unified data management for the whole PDM system. Based on the object management framework is the functional framework of various PDM systems, including product structure management, product configuration management, integration tools, workflow management and so on.

The PDM prototype system is supported by the distributed data processing technology in the network environment, and adopts the client / server (Cl ient/S erver C / S) structure. The server is responsible for the storage of public data and multi-user synchronization, and the client is mainly responsible for the management of customer private data. The overall structure of the system is shown in figure 2. 2.

Figure 2-2 overall framework of PDM system

The bottom layer is the data layer, which uses Cambodia to store the final data of the entire data digging database management system. The data layer adopts distributed storage strategy, uses the way of file system to store picture files and multimedia files, and adopts the form of data encryption and multi-node storage to ensure the security of files. The rest of the data files are stored in database.

The middle layer is the core of the whole PDM system. It provides support for heterogeneous operating environment and heterogeneous data environment. It provides connection and transaction support for multiple operating interfaces. The middle layer can be divided into three sub-layers: interface and protocol layer, component management and access control layer and application system integration layer.

The interface and protocol layer mainly provides transparent data interfaces, data structures and interaction protocols for the component management and access control layer to shield the heterogeneous underlying environment, such as providing H TT P protocol support for web browsers, database drivers such as ODBC, JDB C and so on.

The component management and access control layer mainly provides services for distributed applications in the system. In this layer, component management implements the management of all component objects in the system, access monitoring listens to client requests, accepts client access requests and judges the legitimacy of requests, thus deciding whether to provide corresponding operation services; data control is responsible for directing legitimate access requests. And provide caching, backup and other services for intermediate data; security control ensures that the operation of all column data is legal, and illegal data access outside the system is prohibited; data distribution and replication are responsible for synchronous update and maintenance of distributed database and data mining in data warehouse to ensure that users can get correct information at any time.

The application system integration layer, which is built on the component management and access control layer, is the functional layer of the product data management system. It manages the product data and the processing flow of these data. Provide online user demand feedback, online customer orders, resource reorganization and configuration management, product structure and configuration management, process and workflow management, design retrieval and part library management, program and project management, permissions and user management, inspection and annotation, Internet electronic collaboration, application tool integration and system management and other functions And provide general electronic warehouse and document management and multi-user electronic communication and mail forwarding support.

In order to support Web, it also provides remote transmission support for data files such as pictures, large text, multimedia and so on. In the integration part of application tools, in addition to using file-based encapsulation and API interface to realize the call of application tools and the coordination of related application tools, the system also establishes a unified product data model to realize the integration of some application tools and the system in the underlying data environment. The application tools developed as components are also encapsulated with CORB A standard to realize the seamless connection between them and the system.

The top layer of the system is the user interface. The user interface includes browsers, distributed client applications and C / S application tools.

2. 3 analysis of the main functions of product data management system

In enterprises, a large number of product-related data are often distributed in multi-departments, even in multi-regions, and the formats of these data are diverse, such as text files, databases, picture files, etc., the query, browsing and sharing of these data, as well as the combination of workflow to manage these data, are often encountered by enterprises in the process of information integration.

As the content of PDM is very extensive and the technology is constantly developing, it is difficult to give an accurate definition at present. There are many differences in the global commercialization of PDM products. PDM system provides enterprises with a macro-management and control of all product-related information mechanism.

Generally speaking, an integrated enterprise application PDM system should have the following basic functions: electronic document management function, workflow and design process management function, product structure and configuration management function, view and review function, design retrieval and part library function, project management function, electronic collaboration function, tool and "integration" function, scanning and imaging service function and so on. Here are several main functional modules of PDM.

2. 3. 1 distributed picture and document management

The main purpose of the picture and document management of PDM is to realize: distributed electronic warehouse, the version of picture and document, the unified coding of picture and document, the attribute retrieval and query of graph and document, the use authority and security of document, the unified master model of product data, etc., and provide the storage, retrieval and management functions for distributed heterogeneous data mining.

In PDM, data access is completely transparent to users, users do not need to care about the specific location of electronic data storage, and whether they get the latest version, all these tasks are done by the PDM system. The security mechanism of electronic database enables administrators to define different roles and give them different rights and scope of data access, and by assigning corresponding roles to users, the data can only be obtained or modified by authorized users. At the same time, the release and change of electronic data in PDM must go through a pre-defined approval process before it can take effect, so that users always get the correct information that has been approved.

Electronic reference room is the core of PDM document management, which is based on relational database (such as S QL S er ver). It mainly ensures the security and integrity of data, and supports a variety of query and retrieval functions. Through the associated text records based on the database, users can use the electronic reference room to manage product electronic data documents stored on heterogeneous mediums, such as building complex data models, modifying and accessing documents, and establishing relationships between different types of or heterogeneous engineering data (including graphics and texts, data sequences, documents generated by word processors, etc.). Realize document hierarchy and contact control, package management application systems (such as CAD, CAPP, word processing software, image management and editing, etc.), and easily realize information sharing with product data as the core. The schematic diagram of document management is shown in figure 2. 3

Figure 2-3 schematic diagram of document management

2. 3. 2 product configuration management "

Product configuration refers to the product structure under certain conditions. Product configuration management takes the electronic warehouse as the bottom support and the product structure tree as the operating environment to manage and maintain the product objects and their relationships. Product configuration management can manage product update and deformation information, realize version control, retrieve and query the latest product data efficiently and flexibly, and realize the security and integrity control of product data. Product configuration management enables all departments of an enterprise to share a unified product configuration throughout the product life cycle, and generate corresponding product structure views according to the product definitions of different stages, such as design view, process view, purchasing view and so on.

Product structure and configuration management is to realize the management of product structure and configuration information and bill of materials (BOM _ Bill of Ma terial). It takes the database as the bottom support, takes the parts list of the product drawing paper as its organizational core, connects all the engineering data and documents that represent the final product, realizes the organization, management and control of the product data, and provides different views and descriptions of the product structure to the user or application system under the constraint of certain goals and rules, and generates different BOM. BOM, namely bill of materials, also known as product structure, mainly expresses the relationship between the structure of enterprise products and the components in the products. It is a typical tree structure. In this tree structure, it also includes the number of children required by the parent node.

The product design process generally follows the following four stages of solution development:

(1) definition of requirements

(2) Development and configuration of product functions

(3) develop and configure technical principles to achieve predetermined functions.

(4) develop and configure the mechanism and structure to realize the technical principle.

From the product design process, we can see that the product configuration runs through all the product design stages except the requirement definition. In a sense, product configuration is a product design method, and its biggest advantage is that designers can quickly generate new solutions without making or making appropriate changes on the basis of existing schemes according to the needs of customers. it accelerates the time of all aspects of product development (sales, design, manufacturing), thus greatly shortening the time to market. At the same time, due to the use of mature technology, the quality of new products is guaranteed and the cost is reduced.

The product is made up of a series of interrelated parts, so the product can be decomposed according to the assembly, and the assembly can be further decomposed into components and parts until all of them are broken down into parts. Components are organized according to their assembly relationship, and users can associate all kinds of product definition data information with parts to form a complete description of the product structure. There is a variety of product-related information throughout the product life cycle. This information exists in the form of files and drawings, collectively referred to as drawing documents, including design task books, design specifications, two-dimensional drawing paper, three-dimensional models, technical documents and various process data files.

In PDM system, documents are closely related to objects (products, assemblies, parts). The product structure information tree is formed by associating the document with the parts in the product structure, and its model is shown in figure 2-4. However, it is impossible for enterprises to store all product structures independently, but to manage them by classification. Therefore, for a macro product category, only through configuration can we get a specific product object and have practical significance, so the so-called product configuration is on the premise of meeting the configuration conditions. According to the defined configuration rules to determine which version of the final product, options, alternatives and so on. Product configuration management enables all departments of an enterprise to share a unified product model throughout the product life cycle, easily form variant products, and generate applicable product structure views corresponding to the product information requirements of different stages.

Figure 2-4 Product structure information tree model

The product structure tree can clearly display the assembly relationship of the product, easily query the parts information (such as viewing drawing paper and technical documents, etc.) on the structure tree, and automatically generate a BOM (bill of materials) table according to the product structure tree. at the same time, manage the product structure by establishing the product structure and other product information (such as engineering manual, design document, change order, etc.). It mainly includes the management of the assembly structure of the product itself and the management of its related support data, and effectively manages the product structure by editing, browsing, querying / navigating, comparing the product structure tree and so on.

So that users can view the appropriate structure tree according to their own needs. In addition, the query "where to use" can also be supported. If the parts are used for the supporting data related to product parts in the assembly relationship, including design manuals, design documents (drawing paper, data files), change orders, etc., by establishing the relationship between these data and the structure of product parts, make the management of product structure and document more concise and intuitive.

2. 3. 3 dynamic workflow management

There are three difficulties in workflow management of networked manufacturing platform: dynamic change of business process, large amount of dynamic information exchange and interoperation of heterogeneous services across enterprises in Internet environment. It requires that the workflow management system of networked manufacturing platform can effectively deal with complex business processes, support remote and asynchronous collaboration with large traffic, and has high flexibility and expansibility.

As an important part of PDM system, the task of workflow management is to control the whole formation process of the product and make the process traceable at any time. It is generally believed that the workflow management technology in PDM system is mainly used to track and control the process of product design and modification, including the submission and modification of engineering data, management and supervision, document control and automatic notification. Workflow management is the basis of project management, which mainly manages what happens when a user operates on data, the flow of data between different users, and the activities that track all transactions and data during the life cycle of a project.

The establishment of workflow management system is generally divided into three stages: model establishment, model instantiation and model execution. In the modeling stage, by analyzing the work characteristics and production steps of the enterprise, and using workflow modeling tools or manual operation, the production and operation process model of the enterprise is completed, and the production and operation process of the enterprise is transformed into a workflow model that can be processed by computer. The model instantiation phase sets the necessary parameters for each process (also known as the node in the PDM workflow management), allocates the required resources for each node, and restricts the use rights of the node. The implementation phase of the model completes the execution of the production and management process, mainly the completion of human-computer interaction and application execution.

In the computer-based virtual environment, the information in the workflow reflects the generation process of product data from scratch, from less to more. Therefore, workflow is the processing process of product data. Product data is the basic object of workflow management. From the perspective of timing, workflow contains a series of interrelated tasks. Users use tools (integration programs) to deal with product data when they complete the task. Product data in the workflow is gradually generated and improved with the progress of the task, and is constantly enriched. According to the above analysis. The tasks, product data and users in the workflow are summed up as the three elements of the workflow. The relationship between them is shown in figure 2. 5.

Figure 2-5 three elements of workflow

1. Task

Workflow consists of a series of activities, which are tasks. A task is a series of activities or activities that deal with product data in a certain organizational form in order to achieve a certain purpose. The workflow is divided into tasks according to a certain pattern, and the tasks can be further decomposed into unit tasks. From a management point of view, workflow is the process of completing a series of unit tasks.

Figure 2-6 definition of tasks

2. Product data

The tasks in the workflow deal with all kinds of information, namely product data, including product support data, product definition data and workflow data. These product data are usually represented as various forms of engineering and technical documents. Product support data include: various standards, specifications, standard parts, common parts data, sales data and so on. Product definition data includes product definition model, product diagram, BOM table, design file, calculation book, process file and NC program, etc. Workflow data refers to the issuance, change, examination and approval, signature and other data in the process of completing the task.

With the progress of workflow activities, the design results are produced, and at the same time, these phased design results are the input data and trigger conditions for the next task, that is, the input data is the "trigger" of the task. because the arrival of input data is the beginning of a task, you can use data as the driving force of task activities and "promote" workflow flow. It is necessary to determine the input and output data of the task node to prepare for the "automatic" operation of the workflow.

3. User

In the workflow, different tasks are performed by different users. To accomplish a task, temporarily assign people from different professional and technical backgrounds to dynamically form a multi-functional integrated product development team IPT (Integra t ed Product T eam). IPT is dynamically organized to accomplish specific tasks. When a new task appears, a new team will be created, and as the task is completed, the team will be disbanded.

The general workflow management module is divided into three parts: tool module, project management module and workflow-driven engine module. Among them, the tool module is a collection of many small applications, and its purpose is to facilitate users to set the running environment of the workflow management system. Such as system personnel rights management, project personnel assignment, process template design and other operations can be completed in this module. "process template" is the framework of a certain workflow model and the expression of workflow rules.

The mode of operation of any work can be expressed by the process template-the definition of nodes in workflow management and the relationship between nodes are determined by the process template. A process template can have multiple instances according to different tasks and projects, but these instances manage the workflow according to the rules defined by the template.

A process template contains several "node" and "co nn ector". The node is used to identify a state in the workflow: the connection is responsible for representing the relationship between the nodes. When all the tasks in a node are completed, the person in charge of the node can submit or reject the node. When the node is submitted. The workflow flows forward according to the direction of the connection associated with the node: when the node is rejected, the workflow returns to the node at the next level. Different combinations of nodes and connections can meet the needs of users for different forms of process templates.

2. 3. 4 flexible coding management

Coding is a symbol that endows things or concepts with certain regularity and is easy to be processed by people or computers. it is a technical means for people to unify understanding, unified point of view and exchange of information, and it is the basis of enterprise informatization. Under a complete coding system, information can be transmitted, stored, processed and utilized uniformly, harmoniously and effectively. A good information classification and coding system is the basic guarantee for information integration.

Information coding is the process of information collection, processing, data analysis and establishment of data model. Information coding follows the following principles:

(1) uniqueness principle. You must ensure that only one code is assigned to an encoding object. A code reflects only one coding object, that is, the principle of one thing, one code.

(2) standardization principle. The coding shall adopt the relevant international and domestic standards that have been promulgated as far as possible, and unify the coding form.

(3) the principle of brevity. Under the premise that the code length design meets the application requirements, the coding should be as short as possible to save storage space, data processing and transmission time.

(4) principle of flexibility. When describing different kinds of things, the coding system should be flexible in the number of coding bits and the order of code bits.

(5) the principle of scalability. Scalability should be considered in coding to prevent the coding structure from being reconstructed due to data expansion.

(6) principle of stability. It is necessary to consider the possibility of coding changes and keep the coding relatively stable as far as possible.

(7) principle of identifiability. Reflect the characteristics of the coding object as much as possible, which is convenient for memory and application.

At present, there are many classification and coding systems in the world, some of which have entered the stage of commercial use, but they are not universal, mainly because each system is designed for specific enterprises. Due to the great differences in the production conditions and the types and complexity of processed parts in different industries and factories, it is difficult to achieve universal application. Some factories produce fewer types of parts, which are relatively simple, and it may be enough to use a few code points, while in other factories, there are many kinds of parts and there are great differences in parts, so it may not be enough to use a 15-digit code to classify them. Some features need to be further subdivided, but due to the limitation of the length of the code point, the code point can not be added to meet the requirements. In order to solve such contradictions fundamentally, it is necessary to have a coding system with stronger adaptability and unstable structure. Its characteristic should be that the code point can be long or short, and the code value can contain more or less content, that is, it requires the coding system to be flexible.

2. Information security management of 4PDM system

Product data management (Product Data M an agement _ PDM) is a technology for integrated management of product-related data and processes. PDM system has been implemented in more and more domestic and foreign enterprises, and has gradually become an integrated platform for enterprise informatization. PDM system stores and manages a large number of enterprise sensitive data, so the security and security performance of the system has become an important issue.

PDM system in distributed environment provides the ability to access a large number of information resources, but it is usually accessed through the interface of system data that already exists on I nt e rn et. However, in this new field of distributed systems and information resources, the inherent distributed characteristics of the system make more parts of the system may be attacked by illegal authorized users. In order to prevent the system from internal and external attacks and the loss and destruction of confidential data, thus causing irreparable losses to enterprises, system security has increasingly become a necessary consideration.

2. 4. The concept of 1PDM information security

ISO 748922 divides the security services of an open interconnected system into five categories: authentication, access control, data confidentiality, data integrity and non-repudiation. As an interconnected system, the security service of PDM system is similar. However, in the specific system of PDM, because it is limited to application layer security, data confidentiality and data integrity are redefined as data security, some categories are redescribed, and the analysis of the solution will be limited to these definitions.

(1) Identification. Used to prove that "the user is legal and secure". In fact, it includes two aspects, one is user authentication, the other is connection authentication. The former can use the user management module of the system to identify the legitimacy of user identity; the latter is used to identify the security of users, that is, legitimate users operate through legal paths.

(2) access control. Prevent unauthorized use of resources. In the permission allocation, the data accessible to the object must be encrypted and protected according to different levels. One of the important principles of access control is the "the need _ to _ kn ow". In other words, only one job needs, should know. It can be divided into two aspects, one is to limit the scope of data access for legitimate users, and the other is to prevent illegal users from using resources.

(3) data security. This includes identifying the authenticity of information and protecting information from being disclosed to unauthorized individuals, entities, or processes. That is to ensure that the data can not be forged, the secrecy of the data transmission process and the security of data storage. It includes digital signature, data transmission encryption, data storage encryption and key exchange and so on.

(4) Anti-denial. It provides the receiver of the data with evidence of the source of the data, preventing the sender from attempting to falsely claim that the data has not been sent or to deny its contents. The anti-repudiation of the data receiver can be solved by sending the receipt certificate after receiving. Anti-repudiation is mainly aimed at legitimate users.

2. 4. 2 Construction of Information Security Model

According to the principle of informatics, information is transmitted mainly through source, channel and destination, and the information flow model of PDM system can also be established, as shown in figure 2-7. The source refers to the information input, which is the starting point of the information life of the PDM system; the database is the distribution center of information; and the view is the end point of the specific information flow. Information flow is the embodiment of information life.

PDM system as a large open system, a large number of engineering drawings, process documents, design specifications, product orders and other drawing and document information input, output, storage and flow, the transmission characteristics of information determines that every link of the information in the lifetime of effective information may be the cause of information leakage.

Figure 2-Information flow model of 7PDM system

From the information flow model of PDM system, we can know that the possible harm to PDM system information is as follows:

(1) the original information in the process of information input is leaked, illegal information is entered, or the error of source information is caused by the error of the input personnel.

(2) illegal detection, interception and tampering in the process of information transmission

(3) the information storage period has been illegally consulted, invoked, or tampered with.

(4) illegal peeping, use and tampering in the process of information output.

2. 4. Characteristics and requirements of information security in 3PDM system

The information security features of PDM system are as follows:

(1) PDM system manages a large amount of information. PDM system should manage not only the information of mainframe factory, but also the information of mainframe factory.

Information about the matching factory

(3) there are a large number of people visiting the PDM system, the scope is wide, and the personnel vary greatly. Once the alliance with the collaborative enterprise

When the relationship is terminated, the account corresponding to the staff of the collaborative enterprise must be cancelled immediately.

(4) in PDM system, audit documents, design files and other documents need to be examined and signed, so it is necessary to ensure that the approval documents will not be tampered with in the process of large-scale circulation.

The PDM system must ensure that information can be provided to the right person in the right form at the right time and in the right place. Once any of the three conditions of time, place and personnel are not met, the information cannot exist or exist in its own form. The security requirements of PDM system mainly include:

(1) the confidentiality of information.

(2) the integrity of information. To ensure that the information will not be illegally tampered with and destroyed during the whole information life cycle from the beginning of the input to the information failure. In documents such as design review documents, it is necessary to ensure an one-to-one correspondence between the executor of the information and the information.

(3) the availability of information. Ensure that the information is entered correctly and that the PDM functional module calls and outputs the correct information.

2. 5 summary of this chapter

This article is from Yuyunqing soft Yingtai. For more details, please click: www.plmpdm.cn

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