Chapter 16 The Hierarchical and Network Data Models David M. Kroenke Database Processing © 2000 Prentice Hall

Chapter 16 © 2000 Prentice Hall DL/I “Language for processing a database, implemented in the hierarchical database, IMS (Information Management System) from IBM” Page 453

Chapter 16 © 2000 Prentice Hall DL/I Hierarchical Terms Field “smallest unit of data” Segment “groups of fields; nodes of the tree structure” Data base record “a collection of related segments; a particular tree structure” Data base “composed of database records” Page 453

Chapter 16 © 2000 Prentice Hall DL/I Hierarchical Terms Data base description “how data base records are defined; set of assembly- language macro instructions” Root “first segment” Sequence field “one field in each segment used to order the occurrences of a given type” Page 453

Description of Data Base Page 455 Figure 16-7 © 2000 Prentice Hall

Chapter 16 © 2000 Prentice Hall DL/I Hierarchical Terms Physical data base record (PDBR) “describes the data as it exists in data storage” Logical data base record (LDBR) “describes the data as they appear to the application program” Page 457

Hierarchies Page 456 Figure 16-8 © 2000 Prentice Hall

DL/1 Data Manipulation Commands Page 462 Figure © 2000 Prentice Hall

Chapter 16 © 2000 Prentice Hall CODASYL DBTG Model Conference on Data Systems Languages Data Base Task Group CODASYL also developed standards for COBOL Complex and Incohesive Page 462

Chapter 16 © 2000 Prentice Hall CODASYL DBTG Terms Schema “complete logical view of the database” Subschema “view of the database as it appears to an application program” Data structure description “maps schema records, fields, and relationships to physical storage” Page 462

Chapter 16 © 2000 Prentice Hall CODASYL DBTG Terms User working area “contains database and control data for a particular user” Run-unit “the execution of a program by one of the users” Page 463

CODASYL DBTG Program/Data View Relationships Page 463 Figure © 2000 Prentice Hall

Chapter 16 © 2000 Prentice Hall CODASYL DBTG Terms Data-item “a field that corresponds to an attribute (column)” Record “a collection of data-items” Set “a one-to-many relationship” Page 463

CODASYL DBTG Record Types Page 464 Figure © 2000 Prentice Hall

Two-Owner Record in Different Sets Page 466 Figure © 2000 Prentice Hall

Summary of Set Characteristics Page 467 Figure © 2000 Prentice Hall

Chapter 16 © 2000 Prentice Hall CODASYL DBTG Data Manipulation Language FIND, GET FIND, MODIFY FIND, ERASE Page 470