You know that a database is a collection of logically related data elements that may be structured in various ways to meet the multiple processing and retrieval needs of organizations and individuals. There’s noting new about databases-early ones were chiseled in stone, penned on scrolls, and written on index cards. But now databases ate commonly recorded on magnetizable media, and computer programs are required to perform the necessary storage and retrieval operations.
You’ll see in the following pages that complex data relationships and linkages may be found in all but the simplest databases. The system software package that handles the difficult tasks associated with creating, assessing, and maintaining database records is called a database management system (DBMS). The programs in a DBMS package establish an interface between the database itself and the users of the database, (These users may be applications programmers, managers and others with information needs, and various OS programs.)
A DBMS can organize, process, and present selected data elements from thedatabase. This capability enables decision makers to search, probe, and query database contents in order to extract answers to nonrecurring and unplanned questions that aren’t available in regular reports. These questions might initially be vague and/or poorly defined, bur people can “browse” through the database until they have the needed information. In short, the DBMS will “manage” the stored data items and assemble the needed items from the common database in response to the queries of those who aren’t programmers. In a file-oriented system, users needing special information may communicate their needs to a programmer, who , when time permits, well write one or more programs to extract the data and prepare the information. The availability of a DBMS, however, offers users a much faster alternative communications path.
The management information system (MIS) concept has been defined in dozens of ways. Since one organization’s model of an MIS is likely to differ from that of another, it’s not surprising that their MIS definitions would also vary in scope and breadth. For our purposes, an MIS van be defined as a network of computer-based data processing procedures developed in an organization and integrated as necessary with manual an other procedures for the purpose of providing timely and effective information to support decision making and other necessary management functions.
In addition to what might be termed the horizontal management structure an organization is also divided verticallyintodifferent specialties and functions which require separate information flows. Combining the horizontal managerial levels with the vertical specialties produces the complex organizational structure. Underlying this structure is a database consisting, ideally, of internally and eternally produced data relating to past, present, and predicted future events.
最好不是机译