Basic Definitions 1 Basic Definitions n DATA A

Basic Definitions 1

Basic Definitions n DATA A collection of incoming facts to the organization. Incoming facts data Data processing Information Output DATA-ITEM NAME The context for a recorded data-item is often indicated by a name, such as date, name, age, etc. 2

Basic Definitions DATA-ITEM VALUE It is the specific quantitative or qualitative values given to a specific data-item. For example: If ‘AGE’ is an attribute of some entity and it is equal to ’ 22’, then 22 is the related data value and it is quantitative. And if ‘CITY’ is an attribute of some entity and it is ‘Baghdad’ then ‘Baghdad’ represent the data item value for data-item name CITY, and it’s qualitative. 3

Basic Definitions n GROUP ITEMS AND ELEMENTRY A group item is a collection of closely related items of information. For example DATE usually has three parts, MONTH, DAY, YEAR, when any of there has no further subdivision into meaningful parts they are called ELEMENTRY data-item else the called GROUP data-item or (Aggregate). 4

Basic Definitions n An ENTITY Items about which we store information are referred to as Entities. An Entity may be Tangible object such as: A person (Employee), place (Amman), or thing (parts) An Entity may be Intangible, such as: An event (something happens at a particular time), customer-account, etc. 5

Basic Definitions AN ATTRIBUTE An Entity has various properties which we may wish to record, so that we can recognize, remember, and describe it. These properties are called Attributes. For example: Attributes of human being include items such as: (height, weight, name, age, eye color, ets. ) Attributes of car accident include items such as: (driver-name, time, location, cause of accident, ets. ) 6

Basic Definitions n n RECORD Is a collection of related data-item which share a common context about a particular entity. FILE A file may be defined as a set of (Logical) records all of which related to a particular area of interest. 7

Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and to have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier. 8

Basic Definitions ENTITY IDENTIFIER It is necessary for the programmer or data administrator to be able to refer to a record relating to a given entity, and it is necessary for the computer to be able to identify it and have a means of finding it in the storage unit. For this purpose one of the attributes is usually designated an entity identifier. For example the entity identifier of an employee would be EMPLOYEE-NUMBER. And the entity identifier of an account record would be the ACCOUNT-NUMBER. Some time more than attribute is required in order to identify a record. For example, to identify an airline flight record the FLIGHT-NUMBER and FLIGHT-DATE are needed. 9

Basic Definitions n KEY Is an attribute or a set of attributes which the computer uses to identify a record. PRIMARY KEY Is defined as that key used to uniquely identify one record. Such as ‘STUDENT-NUMBER’, ‘EMPLOYEE-ID’, etc. 10

Basic Definitions CUSTOMER table Data-item name (Attributes) (Fields) Customer-id Customername Customerstreet Customercity 192 -83 Ahmed 23 Alma St. Jbeha 182 -74 Kasim 12 Main St. Sweleh 677 -600 Rana 7 Park Ave. Marka 321 -140 Susan 57 North St. Jabal 710 -569 Tarik 33 Alma St. Jbeha 210 -872 Ali 88 East St. Gardens 11

Basic Definitions CUSTOMER table Data-item name Data-item value Customer-id Customername Customerstreet Customercity 192 -83 Ahmed 23 Alma St. Jbeha 182 -74 Kasim 12 Main St. Sweleh 677 -600 Rana 7 Park Ave. Marka 321 -140 Susan 57 North St. Jabal 710 -569 Tarik 33 Alma St. Jbeha 210 -872 Ali 88 East St. Gardens 12

Basic Definitions CUSTOMER table Primary key Customer-id Customername Customerstreet Customercity 192 -83 Ahmed 23 Alma St. Jbeha 182 -74 Kasim 12 Main St. Sweleh 677 -600 Rana 7 Park Ave. Marka 321 -140 Susan 57 North St. Jabal 710 -569 Tarik 33 Alma St. Jbeha 210 -872 Ali 88 East St. Gardens 13

Basic Definitions CUSTOMER table Records . . Customer-id Customername Customerstreet Customercity 192 -83 Ahmed 23 Alma St. Jbeha 182 -74 Kasim 12 Main St. Sweleh 677 -600 Rana 7 Park Ave. Marka 321 -140 Susan 57 North St. Jabal 710 -569 Tarik 33 Alma St. Jbeha 210 -872 Ali 88 East St. Gardens Customer File 14

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