• Operational, Diagramatic Specifications
- Data Flow Diagrams, Finite State Machines, Petri Nets,
Entity Relationship Diagrams
- UML Diagrams
- Mathematical Specifications
- Simulating models
- Declarative Specifications
• Logic-Based Notations
• Algebraic Notations
- Languages for modular specifications
• Statecharts and Z
What is a specification?
• Specification is a broad term
- Used at various software levels
Different purposes.
- Declaration of Agreement between
• Manufacturers and customers of a service
• Implementers and users
- All desirable qualities need to
specified
What is a specification?
• Specification can be done in different things and in the party
Interested parties such as: (user, projector,
Managers, etc.)
• Specification of requirements:
- Agreement between users and projectors
• Project Specification:
- Agreement between designers and developers.
• Module specification:
- Agreement between SEs using a module and SEs
Implementing a module interface.
• Specification includes "What"
• Implementation includes "How"
Use of specifications
• User needs statement
• Critical Issues
- The user needs may not be understood by
developer.
- Need to verify the specifications.
• Dealing with problems
- Undesirable effects can be severe
Due to misunderstandings between engineers and
Experts Software \
Styles of specifications
• Informal: natural language, Spec Visio / PPT,
Figure, Table, etc.
• Formal: connects to syntax and semantics
- Advantages :
• It may include many formal verifications
• Can Support Automatic Processing
• Includes the use of mathematical models
- Disadvantages :
• Formal specifications are not widely used
• Staff training
• Semi-Formal: Sematic not precise
Specific styles
• Operational
- Describes Desired System Behaviors
- Usually provides a Model Behavior System
- Verified by prototyping
descriptive
- Describes the desirable advantages of the system
- Declarative Specification
- Usually uses mathematical equations
• Both together ...
DATA FLOW DIAGRAMS
Flow charts Data (DFD)
SYSTEM ANALYSIS
• Focuses on a logical system view
And not physical.
• "What" system does not perform as well
• Tools:
- data flow diagrams (DFDs)
- data dictionary (DD)
- specification of the process
- relationship diagrams
Between entities
Data Flow Diagram (DFD)
"A network layout of the system. The system can
Automated, manual or mixed.
DFD describes the system in terms or parts
Component with all interfaces. "
- Tom DeMarco
Therefore DFDs:
Focuses on the data movement between them
External entities and processes and
Between processes and data storage
Data Flow Diagram (DFD) Shows a figure of what people are doing
And procedures transform data into information.
• DFD is composed of four elements .:
- External entity ... source (source) or receiver I
Information (sink)
- The process ... a series of steps to manipulate the data.
Data Guardian ... a place where it is given
Reference for later.
- Data flow ... depicts data and elements
Of information passing between external entities,
Processes and data storage.
Example Data Flow diagram
Data Flow Diagrams are:
• Used to perform the analysis
Structural to determine the requirements
logic .
• A graphic tool, usable for
Sharing between users,
Managers and other personnel.
• Usable for existing analysis
• A simple technique to learn as well used.
Sources / Sinks (hole) 
(External entities.)
• Every class with people, one
Organization, or another system
Which exists outside the system that
We are studying.
• Forms the boundaries of the system.
• The system and external entities
They exchange the data in us
It forms the darkness of it
Data.
• These entities should have one
name
The flow of data
• Moving data
• marks the movement of data through the system -
Of a pipeline to perform the data
• Connects processes, external entities and storage
Of the data.
• One direction
• No leakage control
Processes
• Transform incoming flow
Of the ongoing data
Out.
• Presented by a circle
• Example name combination
VERB / OBJECT examples:
create_exception_report
validate_input_characters
calculate_discount
Data retention
• Data for the rest
• Zone that holds data, processes.
• Appointed
• Only processes are related to
Storage of data.
• Only the launch of the
Data storage and process .per
Example when accessing a DBMS,
Only the flow of
Non-recurring result.
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