In system analysis dfd is the primary step.it shows how the data flows from higher to lower level. which is very crucial to design. without this direct design can be a risky process.
Design is the term used to describe a high level abstraction of a business requirement. Analysis is to take that design broken in detail, but maybe still high level. "Reads an integer and displays True if it is an even number, False otherwise" The "design" may look like: int inputInteger = ReadAnInterger(); GenerateResult(inputInteger % 2 == 0); The "analysis" is to determine how to read that input integer (from what source: console, a file, a window form, a web page, etc), and how to Generate the result "True" and "False" on what (a web page, a window form, the console, or a voice generator, etc)
gate level netlist
Abstraction and refinement are complementary concepts. Abstraction enables you to specify procedure and data internally but suppress the need for "outsiders" to have knowledge of low-level details. Refinement helps you to reveal low-level details as design progresses. Both concepts allow you to create a complete design model as the design evolves.
System design and system analysis are both important stages in the development of a software system, but they focus on different aspects of the process. System analysis is the process of studying and understanding the existing system and its requirements, including its functions, inputs, outputs, and user needs. System analysts work closely with stakeholders to gather and document requirements, create use cases, and develop models of the current system. System design, on the other hand, is the process of creating a new system or modifying an existing system to meet the requirements identified during the analysis stage. System designers use the requirements gathered during the analysis stage to create a detailed design of the new or modified system, including its architecture, components, and interfaces. In summary, system analysis is focused on understanding the existing system and its requirements, while system design is focused on creating a new system or modifying an existing system to meet those requirements. Both are important stages in the development of a software system, and they often overlap and inform one another. Effective system analysis and design can lead to the development of a high-quality software system that meets the needs of its users.
Context Diagram is higher level of abstraction of the whole system. It depicts the various subsystems that interact with each other along with major actors involved. It also gives you what information flows between the modules, actors and system at a high level.
system design The activity of proceeding from an identified set of requirements for a system to a design that meets those requirements. A distinction is sometimes drawn between high-level or architectural design, which is concerned with the main components of the system and their roles and interrelationships, and detailed design, which is concerned with the internal structure and operation of individual components. The term system design is sometimes used to cover just the high-level design activity.
The idea behind viewing a system as a set of layers of abstraction is derived from an old architectural concept called "The Layers of Abstraction Principle." It suggests organizing a system into multiple layers, each representing a different level of abstraction, to manage complexity and promote modularity. This approach makes it easier to understand and modify the system by isolating functionality into distinct layers.
method
=>refers to the level of abstraction above the digital logic level, but below the operating system level. computer organization was created by William salvatiera jr.
Physical level: The lowest level of abstraction describes how a system actually stores data. The physical level describes complex low-level data structures in detail.Logical level: The next higher level of abstraction describes what data the database stores, and what relationships exist among those data. The logical level thus describes an entire database in terms of a small number of relatively simple structures. Although implementation of the simple structures at the logical level may involve complex physical level structures, the user of the logical level does not need to be aware of this complexity. Database administrators, who must decide what information to keep in a database, use the logical level of abstraction.View level: The highest level of abstraction describes only part of the entire database. Even though the logical level uses simpler structures, complexity remains because of the variety of information stored in a large database. Many users of a database system do not need all this information; instead, they need to access only a part of the database. The view level of abstraction exists to simplify their interaction with the system. The system may provide many views for the same database.
3 level of software design - Architecture - Component - Detailed