Third class Software Engineering 2020 The entity relationship

Third class Software Engineering 2020

The entity relationship diagram (ERD) depicts relationships between data objects. The ERD is the notation that is used to conduct the data modeling activity. The attributes of each data object noted in the ERD can be described using a data object description. ﺑﻴﺎﻧﺎﺕ ﻛﺎﺋﻦ ﻛﻞ ﺳﻤﺎﺕ ﻭﺻﻒ ﻳﻤﻜﻦ ﺍﻟﺒﻴﺎﻧﺎﺕ ﻛﺎﺋﻨﺎﺕ ﺑﻴﻦ ﺍﻟﻌﻼﻗﺎﺕ ﻳﻮﺿﺢ ERD )ﻭﺻﻒ ﻛﺎﺋﻦ data object description ﺑﺎﺳﺘﺨﺪﺍﻡ ERD ﻓﻲ ﻣﻼﺣﻈﺘﻪ ﺗﻤﺖ ﺍﻟﺬﻱ ﺑﺎﺳﺘﺨﺪﺍﻡ ERD ﻳﻤﻜﻦ ﻭﺻﻒ ﺧﺼﺎﺋﺺ ﻛﻞ ﻛﺎﺋﻦ ﺑﻴﺎﻧﺎﺕ ﺗﻤﺖ ﻣﻼﺣﻈﺘﻪ ﻓﻲ ( ﺍﻟﺒﻴﺎﻧﺎﺕ . ﻭﺻﻒ ﻛﺎﺋﻦ ﺍﻟﺒﻴﺎﻧﺎﺕ

Data Model The data model consists of three interrelated pieces of information: 1 - Data object 2 - Attributes that describe the data object 3 - Relationships that connect data objects to one another.

There are two basic point in relationship 1 - cardinality: the specification of the number of occurrences of one [object] that can be related to the number of occurrences of another [object]. ﻳﺘﻢ ﻓﻴﻬﺎ ﺗﺤﺪﻳﺪ ﻋﺪﺩ ﻣﺮﺍﺕ ﻭﺟﻮﺩ ]ﻛﺎﺋﻦ[ ﺍﻟﺬﻱ ﻳﻤﻜﻦ ﺃﻦ ﻳﺮﺗﺒﻂ ]ﻛﺎﺋﻦ[ آﺨﺮ : ﻋﺪﺩ ﺍﻟﻌﻨﺎﺻﺮ 1. ﻟﻌﺪﺩ ﻣﻦ ﺍﻟﻤﺮﺍﺕ Taking into consideration all combinations of 'one' and 'many' two [objects] can be related as: 1 -One-to-one (1: 1) 2 - One-to-Many (1: N) 3 - Many-to-Many (M: N)

2 -Modality: The modality of a relationship is 0 if there is no explicit need for the relationship to occur or the relationship is optional. The modality is 1 if an occurrence of the relationship is mandatory. In other words, modality signifies whether a certain data object must participate in the relationship or not. ﺇﺫﺍ ﻟﻢ ﺗﻜﻦ ﻫﻨﺎﻙ ﺣﺎﺟﺔ 0 ﻫﻲ modality : relationship ﺍﻟﻨﻤﻂ ﺍﻭ ﺍﻟﺸﻜﻞ ﻟﻞ 1 ﻫﻲ modality. ﺍﺧﺘﻴﺎﺭﻳﺔ relationship ﺃﻮ ﺍﺫﺍ ﻛﺎﻧﺖ relationship ﻟﺤﺪﻭﺙ ﺑﻤﻌﻨﻰ ﺍﺧﺮ ﺍﻟﻄﺮﻳﻘﺔ ﺗﺴﺎﻋﺪﻧﺎ ﻓﻲ ﻣﻌﺮﻓﺔ. ﺇﻟﺰﺍﻣﺍ relationship ﺇﺫﺍ ﻛﺎﻥ ﺣﺪﻭﺙ . ﺃﻢ ﻻ relationship ﻓﻴﻤﺎ ﺇﺫﺍ ﻛﺎﻥ ﻳﺠﺐ ﻋﻠﻰ ﻛﺎﺋﻦ ﺑﻴﺎﻧﺎﺕ ﻣﻌﻴﻦ ﺍﻟﻤﺸﺎﺭﻛﺔ ﻓﻲ