Database for Libraries -3

In the case of a library we shall be dealing with the following entity sets.
a) The library and its section - The set of all sections including departmental branches of a particular library. Each section name, location and assents.
b) Users-The set of people who have a membership in the library, each user may be described by attributes, Reader code No, Department, or status and address. 
c) Employee - The set of all people who work in the library, each employee may be described by the attribute, employee name and
d) Collection - The set of all documents maintained by the Library. Each document may be described by the attributes, documents No.1. Acc. No. Author, of the said document, total the key word. 
e) Transactions - The set of all users Transactions executed in the library. Each transaction may be described by the attributes, use code, Acc. No. Author, title, date of issue, and due date.
An important task in database modeling is to specify how entities and relationship are distinguished. Individual entities and relationship are distinct, but from database perspective. Their difference must be expressed in terms of their attributes. There is also one limitation of entity. Relationship model is that one cannot express relationship among relationship. One can view a relationship set and its associated entity set as a higher level entity which is treated in the same manner as any other entity.
RELATIONAL MODEL
The relational database model represents the database as a collection of tables. Although tables are simples, intensive motion, there is direct correspondence between the concept of relationship. The user of the database system may query these tables, inert delete the update the tables.
NETWORK MODEL
A network database consists of a collection of record which are connected with each other through links A link is an association between precisely two records. Records are organized in the form of an arbitrary graph.
HIERARCHICAL MODEL
A hierarchical database consists of a collection of records which are connect with each other through links. A record is similar to a record in the network model. Each record is a collection of fields, each of which contains only one data value. It can be single relationship or several relationships. The hierarchical model differs from the network model in that the records are organized as collection of trees rather than arbitrary graphs. 
DATABASE ADMINISTRATION
The database administration is fundamentally a people oriented junction. The main jo0b of the database administration is to coordinate and resolve conflicting needs and desires of users in their required application areas. Database 4 e administration exists within the information systems area of an organizations systems area of an organizations resolved the bias problem by creating information system as an independent staff function, however that still lacked credible authority. 
The most important thing in the data administration is the position of database administrator should not imposed on users. Users must see first the need for such a position, when the position is established user need to encounter positive and helpful attitude, and experience some beneficial results when interacting with the database administrator. In cooperation with users the database administrator seeks to determine what a data to collect and store and criteria used in validating input data and stored data.
The database administration is the key link in establishing and maintaining management and users confidence in the database. They have a mediator to receive both request and complaints. The unique functions of the database administrations are: 
1. Defining, creating, redefining and retiring data.
2. Making the database available to the using environment.
3. Informing and assisting users.
4. Maintaining database integrity.
5. Monitoring operations and performance.