2.1 Define the following terms:
Data Model – a collection of concepts that can be used to describe the structure of a database i.e. the types, relationships and the constraints that should hold good on the data contained in the database.
Database Schema – The description of a database is called its database schema.
Database State – The data in the database at a particular moment in time is called a database state. It is also called the current set of occurrences or instances in the database.
Internal Schema – Internal Schema is one of the major parts of the Three Schema Architecture of a Database. It describes the physical storage structure of the database.
Conceptual Schema –is a map of concepts and their relationships used for databases. The conceptual schema hides the details of physical storage structures and concentrates on describing entities, data types, relationships, user operations, and constraints.
External Schema -- External Schema describes the part of the database that a particular user group is interested in and hides the rest of the database from that user group.
Data Independence – the capacity to change the schema at one level of a database system without having to change the schema at the next higher level.
DDL – DDL or Data Definition Language is used to specify conceptual and internal schemas for the database and mappings.
DML – DML or Data Manipulation Language as the name suggests is used for typical manipulations include retrieval, insertion, deletion, and modification of the data.
SDL –The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.
VDL – VDL or View Definition Language is used to specify user views and their mappings to the conceptual schema.
Query Language -- a high-level DML used in a stand-alone interactive manner.
Host Language -- Whenever DML commands, whether high-level or low-level, are embedded in a general-purpose programming language that language is called the host language and the DML is called the data sub language.
Database Utility -- help the DBA in managing the database system.
Catalog – which contains information such as the structure of each file, the type and storage format of each data item, and various constraints on the data. The information stored in the catalog is called meta-data, and it describes the structure of the primary database.
Client /Server Architecture – The client/server architecture was developed to deal with computing environments in which a large number of PC’s workstations, file servers, database servers, Web Servers and other equipments are connected via a network.
Three Tier Architecture – Three Tier Architecture consists of 3 layers namely – Client, Application Server and Database Server. The Application Server layer accepts requests from the Client, processes them and issues the appropriate command to the Database Server for getting the results.
N Tier Architecture – If the layers of the three tier architecture are further divided into layers of Application Server and Database Server it is called an n- tier architecture.

2.10 Discuss some types of database utilities and tools and their functions.
1. Loading: A loading utility is used to load existing data files into the database. Usually, the current format of the data file and the desired database file structure are specified to the utility, which then automatically reformats the data and stores it in the database.
2. Backup: A backup utility creates a backup copy of the database, usually by dumping the entire database onto tape. The backup copy can be used to restore the database in case of catastrophic failure.
3. File reorganization: This utility can be used to reorganize a database file into a different file organization to improve performance.
4. Performance monitoring: Such a utility monitors database usage and provides statistics to the DBA. The DBA uses the statistics in making decisions such as whether or not to reorganize files to improve performance.

2.11 Think of different users for the database shown in figure 1.2. what types of applications would each user need? To which category would each belong, and what type of interface would each need?

Different users can be: * The registrar office which would basically need to have all the information about the student enrolled in a particular program. It would probably make use of the Student, Course and Section table. * The department in which the student is currently enrolled in. The department need not have the information about the student’s enrolment in the college as a whole. It would basically require its program information related to the students. As a result, the department would probably make use the GRADE_REPORT and the PREREQUISITE table.