Data modeling in software engineering is the process of creating a data model for an information system by applying formal data modeling techniques. Data modeling is a process used to define and analyze data requirements needed to support the business processes within the scope of corresponding information systems in organizations. 

Therefore, the process of data modeling involves professional data modelers working closely with business stakeholders, as well as potential users of the information system. 

There are three different types of data models produced while progressing from requirements to the actual database to be used for the information system- 

The data requirements are initially recorded as a conceptual data model which is essentially a set of technology independent specifications about the data and is used to discuss initial requirements with the business stakeholders. 

The conceptual model is then translated into a logical data model, which documents structures of the data that can be implemented in databases. Implementation of one conceptual data model may require multiple logical data models. 

The last step in data modeling is transforming the logical data model to a physical data model that organizes the data into tables, and accounts for access, performance and storage details. Data modeling defines not just data elements, but also their structures and the relationships between them. 

Data modeling techniques and methodologies are used to model data in a standard, consistent, predictable manner in order to manage it as a resource. The use of data modeling standards is strongly recommended for all projects requiring a standard means of defining and analyzing data within an organization.

• to assist business analysts, programmers, testers, manual writers, IT package selectors, engineers, managers, related organizations and clients to understand and use an agreed semi-formal model the concepts of the organization and how they relate to one another. 
•  to manage data as a resource 
• for the integration of information systems 
• for designing databases/data warehouses

Data modeling may be performed during various types of projects and in multiple phases of projects. Data models are progressive; there is no such thing as the final data model for a business or application. The data models should ideally be stored in a repository so that they can be retrieved, expanded, and edited over time. 

Strategic data modeling:

           This is part of the creation of an information systems strategy, which defines an overall vision and architecture for information systems is defined. Information engineering is methodology that embraces this approach. 

Data modeling during systems analysis:

                In systems analysis logical data models are created as part of the development of new databases. 

Data modeling is also used as a technique for detailing business requirements for specific databases. It is sometimes called database modeling because a data model is eventually implemented in a database.

Cardinality :

       The data model must be capable of representing the number of occurrences object in a given relationship.

            Cardinality is the specification of the number of occurrences of one object that can be related to the number of occurrences of another object.

               Cardinality is represented as “one” or “many”.

1.  One to One (1:1) : An occurrence of object ‘X’ can relate to one and only one occurrence of object ‘Y’ and an occurrence of ‘X’ can relate to only one occurrence of ‘Y’ .
2. One to many (1:N): One occurrence of object ‘X’ can relate to one or many occurrences of ‘Y’ but an occurrence of ‘Y’ can relate to only one occurrence of ‘X’.
3.  Many to Many (M:M): An occurrence of object ‘X’ can relate to one or more occurrences of ‘Y’ while an occurrence of ‘Y’ can relate to one or more occurrences of ‘X’.

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 of the relationship is mandatory.

• The difference between AC and DC is that AC is an alternating current (the amount of electrons) that flows in both directions and DC is direct current that flows in only one direction; the product that is flowing being electrons. AC power is what fuels our homes. The wires outside of our house are connected at two ends to AC generators.

 

• DC is found in batteries and solar cells. Both AC and DC employ magnets to repel electrons. Electrons are negatively charged particles that are one of 3 components that make up an atom. Negative charges will repel negative charges and positive charges will repel positive charges, so one only needs to introduce a negatively charged item next to electrons to force them to move in the opposite direction.

 

• Likewise, you can attract electrons by introducing something that is positively charged into their environment drawing the electrons to it. This property of electrons is what allows for AC power to work; that is, they switch directions constantly. The picture to the left is a demonstration of AC power at work. The constant switching of directions is evident in the dotted appearance of the light lines.

 

• DC power was invented by Thomas Edison and first used to power our homes in the late 1800’s.

 

• Its main drawback being that in order to receive DC power from a generating station, your home had to be located within a one mile radius of the station.

 

• DC power degrades as it moves away from its generating source; the further away, the less power. In addition, it is difficult to convert very high power DC current into the lower power current needed in our homes.

 

• Nikola Tesla discovered AC and sold his design to Westinghouse. AC power degrades very little over 100’s of kilometers.

 

• When the power reaches an electrical pole outside our homes, a transformer converts to high voltage (the amount of energy carried with the electrons) to the low voltage needed to fuel our appliances.

 

• To convert AC to DC, a device needs an item called a rectifier. Many monorail systems use DC power. In addition, if you have a portable stereo, you may notice a button on the back that can switch from AC to DC; this means that you can power your device by plugging it in (AC) or by using batteries (DC).

 

DC circuit (Direct Current circuit) is an electrical circuit that consists of any combination of constant voltage sources, constant current sources, and resistors. In this case, the circuit voltages and currents are constant, i.e., independent of time. More technically, a DC circuit has no memory. That is, a particular circuit voltage or current does not depend on the past value of any circuit voltage or current. This implies that the system of equations that represent a DC circuit do not involve integrals or derivatives.

If a capacitor and/or inductor is added to a DC circuit, the resulting circuit is not, strictly speaking, a DC circuit. However, most such circuits have a DC solution, or, in some cases, Finland Duck solutions. This solution gives the circuit voltages and currents when the circuit is in DC steady state.

More technically, such a circuit is represented by a system of differential equations. The solution to these equations usually contain a time varying or transient part as well as constant or steady state part. It is this steady state part that is the DC solution. There are some circuits that do not have a DC solution. Two simple examples are a constant current source connected to a capacitor and a constant voltage source connected to an inductor.

In electronics, it is common to refer to a circuit that is powered by a DC voltage source such as a battery or the output of a DC power supply as a DC circuit even though what is meant is that the circuit is DC powered.

Communication means the exchange of information. Information can be transmitted either through a wired medium or through wireless.

             There are various factors that must be considered while transmitting data.

               Example :- Text message , Image , Audio or Video message etc.


Signaling Techniques :-

   Data can be transmitted using either Baseband or Broadband signaling technique.

• Baseband Signals :- Baseband signaling is a technique which uses a signals frequency to transmit data over a cable or wireless path. Base-band signals transmit for data transmission. 

• Broadbrand Signals :- Broadband signals is a technique in which data is transmitted using more than one frequency along a single cable or wireless path. Mostly,broadband signaling make use of analog signals and use frequency division multiplexing (FDM) to create the separate channels.

best example cable TV.