The description schema separated from the data

Chapter2 Review Questions

2.1. Define the following terms: data model, database schema, database state,
internal schema, conceptual schema, external schema, data independence, DDL, DML, SDL, VDL, query language, host language, data sublanguage, database utility, catalog, client/server architecture, three-tier architecture, and n-tier architecture.

conceptual schema: describes the structure of the whole database for a community of users. The conceptual schema hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints. Usually, a representational data model is used to describe the conceptual schema when a database system is implemented. This implementation conceptual schema is often based on a conceptual schema design in a high-level data model.

external schema: The external or view level includes a number of external schemas or user views. Each external schema describes the part of the database that a particularuser group is interested in and hides the rest of the database from thatuser group. As in the previous level, each external schema is typically implemented
using a representational data model, possibly based on an external schema design in a high-level conceptual data model.

The XML model: self-describing data models. The datastorage in systems based on these models combines the description of the data with the data values themselves.

In traditional DBMSs, the description (schema) is separated from the data. These models include XML (see Chapter 12) as well as many of the key-value stores and NOSQL systems (see Chapter 24) that were recently created for managing big data.

2.7. Discuss the different types of user-friendly interfaces and the types of users
who typically use each.

2.8. With what other computer system software does a DBMS interact?

applications would each user need? To which user category would each belong, and what type of interface would each need?

2.13. Choose a database application with which you are familiar. Design a schema
and show a sample database for that application, using the notation of Figures
1.2 and 2.1. What types of additional information and constraints
would you like to represent in the schema? Think of several users of your database, and design a view for each.