Hierarchical and Network Data Models

Question-and-Answer flashcards covering definitions, advantages, disadvantages, examples, and key concepts of the hierarchical and network database models.

What basic structure does the hierarchical data model resemble?

An upside-down tree with parent and child segments.

In a hierarchical model, how many parents can a child segment have?

Exactly one.

Name one advantage of the hierarchical model.

It is easy to understand and visualize (also efficient for naturally hierarchical data and relatively easy to implement).

Give one disadvantage of the hierarchical model.

It is not as flexible as other data models (also difficult to update and not highly scalable).

What is a segment in the context of the hierarchical model?

A structured set of data elements similar to a file system’s record type.

Which early IBM database helped put humans on the moon and used the hierarchical model?

IMS (Information Management System).

What key limitation of the hierarchical model led to the creation of the network model?

Its inability to represent complex non-hierarchical relationships.

How does the network model represent relationships between records?

Through pointers that link interconnected records, allowing multiple parents for a record.

State one advantage of the network model over the hierarchical model.

Greater flexibility and ability to represent complex relationships.

List one disadvantage of the network model.

It is harder to understand and visualize than the hierarchical model (also difficult to update and less scalable than relational models).

Why did programmers find the network model cumbersome for reporting?

It lacked built-in query capabilities, requiring custom code for even simple reports.

What is a schema in database terminology introduced by the network model?

The conceptual organization of the entire database as seen by a DBA.

Define subschema.

The portion of the database that applications can see and interact with.

What does DML stand for and what is its purpose?

Data Manipulation Language; commands used to interact with and manage the data (e.g., SELECT, INSERT, UPDATE, DELETE).

What does DDL stand for and what does it do?

Data Definition Language; commands that create, alter, and drop schema components in a database.

Name one network database still found in some enterprises today.

Adabas (others include IDMS and ICL DMS).

Which generation of data models includes the hierarchical and network models?

The second generation of data models.

For what kind of real-world data might a network model be preferable to a hierarchical model?

Non-hierarchical structures such as organizational charts or family trees where an individual may have multiple supervisors or parents.