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Nomad Software is a relational database and fourth-generation language (4GL), originally developed in the 70s by time-sharing vendor National CSS, Inc. While it is still in use today, its widest use was in the 70s and 80s. Nomad provides both interactive and batch environments for data management and application development, including commands for database definition, data manipulation, and reporting. All components are accessible by and integrated through a database-oriented programming language. Unlike many tools for managing mainframe data, which are geared to the needs of professional programmers in MIS departments, Nomad is particularly designed for (and sold to) application end-users in large corporations. End-users employ Nomad in batch production cycles and in Web-enabled applications, as well as for reporting and distribution via the Web or PC desktop. ==Capabilities== Nomad is distinguished by five characteristics: *An intuitive database-oriented 4GL for creating databases, managing data, and writing applications *An interactive environment in which any 4GL statement may be typed and immediately processed (comparable to interactive tools like PHP or Perl) *Relational database features, supporting lookup tables and the other elements of a normalized relational database *Powerful set-at-a-time operations under the control of simple imperative commands *Accesses data from many sources, such as VSAM, IMS, IDMS, DB2, Oracle, and SQL Server. Nomad's language was designed to simplify the application development process, especially for reporting applications. Where possible, common requirements were addressed by intuitive nonprocedural syntax elements, to avoid traditional programming. The heart of the system was the LIST command, which created report output. In this example, database fields STATE, CUST_ID, NAME, PHONE, STATUS, and BALANCE are laid out on a grid, with two sort breaks (via BY), generated columns based on data values (via ACROSS), and data selection (via WHERE). Additional keywords could control subtotals, titles, footers, table lookup, and myriad reporting details. The LIST command is somewhat analogous to the SQL SELECT statement, but incorporates formatting, totaling, and other elements helpful for tailoring output to a business requirement. The SELECT statement, in contrast, is essentially a data query tool: its results would be processed or formatted as required using other mechanisms. This distinction is highlighted by SQL's classification as a 'Data Sublanguage' (DSL): SQL is a powerful formalism for controlling ''data retrieval.'' The LIST command is a comprehensive ''report writer'' addressing broader functionality. Another example of Nomad's power is illustrated by Nicholas Rawlings in his comments for the Computer History Museum about NCSS (see citation below). He reports that James Martin asked Rawlings for a Nomad solution to a standard problem Martin called the ''Engineer's Problem'': "give 6% raises to engineers whose job ratings had an average of 7 or better." Martin provided a "dozen pages of COBOL, and then just a page or two of Mark IV, from Informatics." Rawlings offered the following single statement, performing a set-at-a-time operation, to show how trivial this problem was with Nomad: CHANGE ALL SALARY=SALARY Rawlings continues: "() decided to drop the idea (showing alternative solutions to the problem ). (Nomad solution ) was too unbelievable for him. He published his book in 1982 (1981 ), with many fine examples of NOMAD, most of which look silly today, for they don't reflect what NOMAD was really used for in the years since: serious, mission critical applications. I used Martin's Engineer's Problem in hundreds of NOMAD classes, as I forced people to think in terms of sets of data, instead of record-at-a-time, which is how they'd been taught." 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Nomad software」の詳細全文を読む スポンサード リンク
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