- to show the
process and function of the system and data flow among the processes. It also shows
the data files used in the processes.
e.g. Data Flow
Diagram & Structured Design
Data Flow Diagram
-System analysis
and design tool that graphically show the flow of data in a system
- Used to show the
process and function of the system
- Show the flow of
data among the processes/entities
Example:
Ticket System
Structured Design
- Program design
that uses graphical description tools (Structured chart). This approach involves
breaking the programming into logical manageable portions of modules
Example:
2) Conceptual Data Modelling
- shows entities relationship, system structure and relation among the
data. e.g. Entity Relationship Diagram (ERD)
ERD
- A diagram that uses graphical concept to show the data flow from one entity
to another entity by using types of relation and cardinality.
Chen Notation
An entity is an object or concept about which you
want to store information.
A weak entity is an entity that must defined by a foreign key relationship with another entity as it cannot be uniquely identified by its own attributes alone.
Actions, which are represented by diamond shapes, show how two entities share information in the database. In some cases, entities can be self-linked. For example, employees can supervise other employees.
Attributes, which are represented by ovals. A key attribute is the unique, distinguishing characteristic of the entity. For example, an employee's social security number might be the employee's key attribute.
A multivalued attribute can have more than one
value. For example, an employee entity can have multiple skill values.
Connecting lines, solid lines that
connect attributes to show the relationships of entities in the diagram.
Cardinality specifies how many
instances of an entity relate to one instance of another entity. It is always linked
to a relationship to connect one entity to another entity.
Source:
UML Notation
3) Logical Modelling
- Shows what a system is or what it does and
illustrates the logical part of a system and thus ignore the technical and
implementation independent
- e.g. Pseudocode/Flow Chart/Decision Table
Pseudocode
- an informal high-level description of the
operating principle of a computer program or other algorithm
Flow Chart
- a
diagram that shows a process, system or computer algorithm
Decision Table
- Table that lists a variety of condition and the
action that correspond to each condition
- System analyst can use decision table to show the
detail process of new system consists of many condition or rules
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