4.5.3 Entity Relationship Diagram
REMOVE
ExId
LName
EMPLOYEE
EXPATRIATES
1-1
1-1
DOB
Sex
1-1
1-N
REN
FNam
Phones
FName
email
LOCATE
email
LNam
EmpI
WORK
Phones
Club of language
1-1 1-1
DOB
1-N
Sex
HOUSES
SERVICES
School
SerId
Hospital
1-1
Web list
Name
HouId
1-N
1-1
Market
POSSESS
ORGANIZATION
Price
Rooms
1-1
HAS
Website
1-N
1-N
OWNER
POBox
LOCATIONS
FName
Phones
Region
Name
OrgId
email
LName
District
Street LocId
email
OwId
DOB
Phones
Sex
Figure 12: Entity Relationship Diagram for HRRSS
30
4.6 CONCEPTUAL MODEL OF DATA
CMD has for goal to write under a formal way data that will be
used by the management information system. It is exactly a representation of
data, easily comprehensible, permitting to describe the system of information
by use of entities. This diagram permits to represent the structure of the
system of information for the data; this means the dependences or the relations
between different data.
The intervening elements in the modeling of the conceptual model
of data are:
Entity: an entity is the representation of a
material or immaterial element having a role in the system that is to be
described.
Attribute: An attribute is a characteristic of an entity that we
want to record or retrieve later. Data : A data is the element
of an entity. It is the most important element of database. Identifier:
is a set of properties (one or several) permitting to designate one
and a unique entity; it is a particular property of an object as there can't
exists two occurrences of this object for which this property could take the
same value.
Association: It makes possible to connect one
or more entities. These connections are stated via management rules. Contrary
to the entity, association is named with a verb. There are different
association's types.
Cardinalities: Cardinalities are a couple of values (minimum,
maximum).
The minimum cardinality corresponds to the minimal number of
times that each entity occurrence takes part in the association occurrences. It
generally takes values 0 or 1. The maximum cardinality corresponds to the
maximum number of times where each occurrence of the entity takes part in the
occurrences of association. It is at least equal to 1. The infinite one is
noted «N».
|
Cardinality
|
Signification
|
|
1,1
|
One-to-one
|
|
1,N
|
One-to-many
|
Table 1: Cardinalities
31
4.7 LOGICAL DATA MODEL
Logical data models represent the abstract structure of some
domain of information it will Includes all entities (tables), attributes
(columns/fields) and relationships (keys) , Is independent of technology
(platform, DBMS), Is normalized to fourth normal form (4NF) used in development
of this system.
1. ORGANIZATIONS (OrgId, Names, email, website,
POBox, Phones, LocId);
2. EMPLOYEES (EmpId, LName, FName, Sex, DOB,
Phones, email, OrgId );
3. LOCATIONS (LocId, Street, Region,
District);
4. LOCATE (LoId, ExId, SerId);
5. EXPATRIATES (ExId, LName, FName, Sex, DOB,
Phones, email, OrgId, HouId);
6. OWNERS (OwId, FName, LName, DOB, Sex, email,
Phones);
7. HOUSES (HouId, Names, Price, Rooms, OwId,
LocId, ExId);
8. SERVICES (SerId, HosId, CluId, MarId, SchId,
CluId, LocId).
9. MARKETS(MarId, Names, email, POBox, Phones,
SerId);
10. SCHOOLS(SchId, Names, email, POBox, Phones,
SerId);
11. HOSPITALS(HosId, Names, email, POBox,
Phones, SerId);
12. CLUBS(CluId, Names, email, POBox, Phones,
SerId);
13. WEBLIST(weId,Job title, Company, Link,
SerId);
14. LOGIN (LogId, Uname, Pword,
Ftion);
15. ARCHIVE (ArcId, SerId, HouId,
EmpId,ExpId).
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