Which of the following database products implemented the CODASYL DBTG network data model?

Introduction / Context:
Before the widespread adoption of the relational model, database systems were often based on hierarchical or network data models. The CODASYL Data Base Task Group (DBTG) defined a standard for network databases that influenced several commercial products. Knowing which products implemented which data models helps you understand the historical evolution of databases and why relational systems became dominant later. This question asks you to identify a product that implemented the CODASYL DBTG network model.

Given Data / Assumptions:

• The CODASYL DBTG model refers to the network data model defined by the CODASYL committee.
• Several commercial products appeared that followed this specification.
• The options list well known database products from different eras.
• We assume standard historical information from database literature.

Concept / Approach:
The CODASYL DBTG model is a network data model that uses record types and set types to represent data and relationships. It differs from the relational model by providing more explicit navigation through sets. IDMS, which stands for Integrated Data Management System, is a classic network database system that implemented the CODASYL DBTG specifications. By contrast, DB2 is IBM's relational database, dBase II is a desktop database product influenced by different models, and R base is an early relational system. Thus, IDMS is the correct choice when asked about CODASYL DBTG implementations.

Step-by-Step Solution:
Step 1: Recall that CODASYL DBTG defined a network data model.Step 2: Identify which products among the options are network model based rather than relational.Step 3: Recognize that IDMS is widely documented as a CODASYL style network database.Step 4: Note that DB2, dBase II, and R base are associated with relational or other models, not CODASYL network.Step 5: Conclude that IDMS is the database product that implemented the CODASYL DBTG model.

Verification / Alternative check:
To verify, you can recall that IDMS was often mentioned alongside CODASYL in early database books and that it used navigational access via set relationships. It allowed programmers to move from record to record along predefined paths, which is characteristic of the network model. In contrast, DB2 is famous for its SQL interface and relational tables, and dBase II is known as a file based system for desktop use. This clear separation confirms that IDMS is the CODASYL DBTG implementation among the listed options.

Why Other Options Are Wrong:
Option B, DB2, is IBM's flagship relational database system and is not based on the CODASYL network model. Option C, dBase II, is a database management system for microcomputers that uses its own file formats and does not implement CODASYL DBTG. Option D, R base, is an early relational database for personal computers, again not built on the CODASYL specifications. Only IDMS matches the network model background described in the question.

Common Pitfalls:
Students sometimes classify all pre relational systems together without distinguishing between hierarchical and network models or between different commercial products. Another pitfall is to assume that any older database must be CODASYL based, which is not true. Understanding that IDMS is historically linked to the CODASYL DBTG network model helps clarify these distinctions and gives you a clearer picture of database history.

Final Answer:
The database product that implemented the CODASYL DBTG network data model is IDMS, which corresponds to option A.