Computer Science and Technology Encyclopedia

Author: Editor-in-Chief: Zhang Xiaoxiang
Publisher:
Publish Date: 1998-08-01
Features: Fragment: Backus-Naur form (BNF) is a formal system used to describe the syntax of programming languages. It is named after J. Backus of the American IBM Corporation and Professor P. Naur of the University of Copenhagen, initially used for the syntax of ALGOL60 language, and is a typical meta-language. BNF can also be considered an acronym for Backus-Naur form, Backus-Normal form, and Backus-Normal formalism. It can strictly represent the local grammar rules of a class of context-free languages. Therefore, since it was adopted by the ALGOL60 language text, it has been widely promoted and is commonly used in various computer programming languages. The method of BNF to represent grammar rules is as follows: non-terminal symbols are enclosed in angle brackets. The left side of each rule is a non-terminal symbol, and the right side is a string composed of non-terminal symbols and terminal symbols, separated by ∷＝. Rules with the same left side can share one left side, and the right sides are separated by a vertical bar |. For example, a set of BNF formulas defining identifiers is:
〈Identifier〉：：＝〈Letter〉｜〈Identifier〉〈Letter〉〈Identifier〉〈Digit〉〈Letter〉：：＝a｜b｜c｜…｜z
〈Digit〉：：＝0｜1｜2…｜9
(Cheng Hu)
Backus normal form (BNF) precisely describes the syntax of programming languages as a formal system. Also known as Backus-Naur form, it is abbreviated as BNF (BNF can also be considered an acronym for Backus Normal Form or Backus-Naur Formalism). Computer scientist Backus and Naur first used it to describe the syntax of programming languages, hence the name. The syntax components of programming languages, such as identifiers, expressions, and sentences, can mostly be described using BNF production rules. BNF production rules only use two meta-symbols: one is "∷＝," which means "defined as," and the other is "｜," which means "or." Each rule contains exactly one "∷＝," dividing the rule into left and right parts. The left side is a defined non-terminal symbol (representing a syntax component, usually with a specific meaning), and the right side is a string composed of non-terminal symbols or/and terminal symbols, or several such strings separated by "｜." Here, terminal symbols refer to the basic characters of the programming language character set. For example:
〈Binary Digit〉：：＝0｜1
〈Decimal Digit〉：：＝0｜1｜2｜3｜4｜5｜6｜7｜8｜9
define binary digits and decimal digits, respectively.
The right side of the production rule can also include other already-defined non-terminal symbols. For example:
〈Digit〉：：＝〈Binary Digit〉｜〈Decimal Digit〉
The right side of the production rule can also include the non-terminal symbol on the left side that is currently being defined, indicating a recursive definition. For example:
〈Identifier〉：：＝〈Letter〉｜〈Identifier〉〈Letter〉｜〈Identifier〉〈Digit〉
defines "identifier" as a letter-prefixed alphanumeric string.
Since BNF was first adopted in the ALGOL60 language text, it has been widely used in many computer disciplines.
References:
Chen Huowang et al. Principles of Compiler for Programming Languages. National Defense Industry Press, 1984 (Chen Huowang, Bian Kerong)
Bang0ngxinxixitong
Office Information System (OIS) is a man-machine information system composed of office personnel and office equipment, aimed at improving office efficiency and effectiveness. Office equipment generally includes computers (hardware and software), communication, word processing, and printing equipment, with computers as the core. Office information systems involve disciplines such as behavioral science, systems science, computing technology, and communication technology. It is a man-machine system, where equipment and resources (including data and software) are important conditions, but people are the decisive factor in office work. The data it handles has evolved from single text data to multimedia data including text, voice, graphics, images, animation, and video. The term "Office Information System" evolved from "Office Automation (OA)." As society develops, the proportion of employment related to office work continues to grow, making the improvement of office efficiency and quality a prominent issue. The term "Office Automation" was first coined in 1936, meaning the use of single devices like typewriters and telephones to assist office staff in handling office tasks. In the 1960s, electronic technology made significant progress, and tasks such as billing, accounting, and payroll began to be handled by computers, leading to faster development of office automation technology in the West. In the mid-1970s, advanced office equipment such as multi-function telephones, copiers, fax machines, and word processors continued to appear; new technologies like local area networks and databases were applied in office automation; and the scope of office automation gradually expanded to cross-city and even global scales. Office automation has evolved from an early local technology into a multi-functional information system, marking a qualitative leap. In early 1980, C.A. Ellis of the United States believed that the term "Office Automation" was easily misunderstood and suggested changing it to "Office Information System." After the mid-1980s, with the rapid development and widespread application of microcomputers, email, window interfaces, multimedia, and electronic data exchange in OIS, office information systems had evolved into comprehensive office systems combining communication and computing technologies. In 1988, the Special Interest Group on Office Automation (SIGOA) of the Association for Computing Machinery (ACM) was renamed the Special Interest Group on Office Information Systems (SIGOIS), but internationally, OIS and OA remain in common use.
Goals and Target Audience
Office information systems provide information services to office staff through means such as data collection, storage, transmission, management, and processing, aiming to improve office efficiency and quality, thereby achieving economic and social benefits. The widespread adoption of office information systems has led to changes in office organizational structures, work methods, and processes, placing new demands on the existing office workforce while also creating many new job opportunities. The target audience of office information systems includes senior leaders, general managers, business personnel, secretaries, and operators. Senior leaders at the organizational level are primarily used for strategic decision-making, focusing on macro-level information. Departmental leaders play a key role in tactical decision-making within their departments, focusing on departmental management information. General managers and business personnel handle their respective business operations and management. Secretaries and operators are mainly engaged in transactional operations.
Office Models
An office model is an abstraction of the office process. Different models can be established based on different office perspectives:
(1) Information flow models focus on the transmission of information flow, such as the Information Control Network model (ICN, 1979) and the Table Flow Model (FFM, 1980);
(2) Activity models are based on office activities or processes, such as the SCOOP model described by Petri nets (1977) and the Office Task Management Model (OrM, 1988);
(3) Functional models are based on office functions, such as the Functional Entity Model (1984) and the Conceptual Model (1987);
(4) Semantic models introduce concepts from databases and artificial intelligence, such as the OMEGA model embedded in knowledge languages (1983);
(5) Socio-political models do not focus on office behavior itself but emphasize its social role, i.e., interpersonal relationships and knowledge exchange, considering the office process as a series of conflicting, negotiated interactions, such as the Actor Model (1984).
Office models are primarily used for system description and explanation, dynamic simulation of office activities, and system comparison. They are tools for designing and evaluating office information systems.
Hierarchical Structure
According to function, office information systems can be divided into three levels: transaction processing, information management, and decision support.
(1) Transaction Processing Layer
This is the most basic level of an office information system, primarily providing operational services and assisting office staff in handling daily office tasks using modern office equipment. Its foundation is word processing, including text editing, table processing, electronic printing, document management, schedule management, project management, resource management, and email. Office software packages, various word processing software, table processing software, and graphical interface software are all basic software at this level.
(2) Information Management Layer
This layer primarily provides information services, supported by databases, offering information in areas such as planning, personnel, finance, production, supply and distribution, inventory, energy, transportation, policies and regulations, economic dynamics, and market information.
(3) Decision Support Layer
This layer primarily provides decision-making services, constructing corresponding mathematical models for specific issues based on the needs of senior leadership to assist in decision-making. For semi-structured and unstructured problems, artificial intelligence techniques such as expert systems and neural networks are often required.
Types
According to the highest level of support an office information system can provide, it can be divided into transaction processing, information management, and decision support types. Office information systems can also be divided into several levels based on the organizational structure they serve, such as central government departments, provincial and municipal offices, county offices, and enterprise-level office information systems (e.g., headquarters, branches, factories, workshops). Each level can further be divided into several subsystems based on function. Office information systems can also be categorized based on industry characteristics, such as:
(1) Transaction-based: Primarily focused on text processing and transaction processing, such as document systems, order processing, civil aviation ticketing, editing and publishing, and libraries;
(2) Professional: Serve various professional institutions, such as law firms, accounting firms, auditing firms, and design institutes;
(3) Case-based: Primarily focused on cases, such as office information systems for courts, public security, and hospitals;
(4) Production-based: Primarily focused on production management, involving production planning, organization, command, and control, with business management as a secondary focus, also known as production-oriented office information systems.