Online ordering and inventory system

4.7 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 exist 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».

Table 1: Cardinality

Cardinality	Signification
1,1	One -to- one
1, N	One -to-many

4.8 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. CUSTOMERS (CustomerId, Adress, InvoiceId, username, password, Email, Regdate, Phone)

2. PRODUCT (ProductId, Prodcategory, Prodname, Proddescription, Image, Prodprice)

3. INVOICE (Invoiceid, Prodid, pricetotal, Unitprice, Date, Quantity)

4. ORDER (Orderid, Orderdate, Customername, Quantity, Prodname, Prodid, Companyname, Deliverydate)

5. STOCK (Codestock, Prodid, regdate, Quantity)

6. DELIVERY (DeliveryId, product, Quantity, Customer, Datereceivable)

7. AUTORIZED STAFF (Id, name, Adress, Companyname)

8. CONTAIN(ProdId, InvoiceId, DateofCreate)

9. MAKE (CustomerId, OrderId, Productname)

10. PAY (CustomerId,InvoiceId,ProductId)

11. HAS (ProductId, Productname, StockId)

12. CONTAINS (OrderId, DeliveryId, Date)

13. AUTHORIZE (DeliveryId, Id, date of receivable)

4.9 The Conceptual Level

4.9.1 The Treatment Conceptual Model

The conceptual model of treatment permits to treat the dynamism of the information system, it means that operations are achieved according to events. This model permits to represent schematic way the activity of an information system without making reference to organizational choices or the means of execution therefore. That is to say it allows defining what must be done merely, but it doesn't say when, how, nor where.

The event

An event represents a change in the outside environment to the information system; it can also represent a change in the information system itself.

An external event is a change of the outside universe of the information system

Symbol used:

An internal event is an internal change to the information system

Symbol used: