This document provides an overview of the basic concepts and components of the CODASYL network model for database design. It describes how data is represented using record types and links, how relationships are modeled, and how data structure diagrams depict the logical structure of a database. It also explains how the CODASYL model maps networks to files using pointers and ring structures, and how the DBTG (Data Base Task Group) implementation facilitates data retrieval, updating, and set processing using commands, program work areas, and currency pointers.

7. Network Representation of Ternary Relationship

14. Example Schema

41. Example Ring Structure

45. Sample Database

46. Two Data-Structure Diagrams

47. Sample Database Corresponding to Diagram of Figure A.3b

48. Sample Database Corresponding to Diagram of Figure A.6b

49. Sample Database Corresponding to Diagram of Figure A.8b

50. Two Data-Structure Diagrams

51. Sample Database Corresponding to the Diagram of Figure A.11

52. DBTG Set

53. Three Set Occurrences

54. Data-Structure and E-R Diagram

55. A customer Record

56. Clustered Record Placement for Instance for Figure A.1

57. Class Enrollment E-R Diagram

58. Parent—Child E-R Diagram

59. Car-Insurance E-R Diagram