Computer Systems Design - Concepts and Principles
System Design defines the process of applying certain techniques and principles in order to define a device, a process or system in sufficient detail to allow interpretation and physical performance.
The System Design phase involves four stages:
The design of data
Transforms the domain model of information created during the analysis, data structures needed to implement the software.
Architectural Design
Define the relationship between each of the structural elements of the program.
Interface Design
Describe how the software communicates with himself, operating systems and with the operators and users who use it.
The design procedures
Transform structural elements of the program architecture. The importance of software design can be defined in one word Quality in design is where it promotes the quality of the project. Design is the only way to realize the exact customer requirements.
The software design is a process and a model at a time. The design process is a set of repetitive steps that allow the designer to describe all aspects of the system to build. Throughout the design assesses the quality of project development with a set of technical reviews:
The design must implement all the explicit requirements contained in the analysis model and must accumulate all the implicit requirements desired by the customer.
It should be a guide who can read and understand those who build the code and tested and maintained that the Software.
The design must provide a complete idea of what the software, analyzing data domains, functional and behavior from the viewpoint of Implementation.
To assess the quality of a design submission, we must establish technical criteria for good design such as:
* A design must present a hierarchical organization that makes smart use of control among software components.
* The design must be modular, ie, it must be a logical partition of the Software on elements that make specific functions and subfunctions.
* A design must include data and procedural abstractions.
* Must produce modules which exhibit characteristics of independent functioning.
* It should lead to interfaces that reduce the complexity of the connections between the modules and the external environment.
* You must produce a design using a method that could be repeated according to information obtained during software requirements analysis.
These criteria are not achieved by chance. The software design process requires good quality through the application of fundamental principles of Design, Methodology systematic and comprehensive review.
When you are designing a computer system should be aware that the design process includes design and planning something in mind and make a design or sketch.
Design Output
In this case refers to output results and information generated by the system, for most users the output is the only reason for developing a base system and evaluate its utility. But when performing a system, as analysts must do the following:
* Determine what information to present. Decide whether the information will be presented in a visual, verbal or printer and select the output medium.
* Arrange the presentation of information in an acceptable format.
* Decide how to distribute the output among the possible recipients.
Design Files
It includes decisions about the nature and content of the file itself, as if he would use to store details of transactions, historical data or reference information. Among the decisions taken during the design file, include the following:
* The data to be included in the format of records in the file.
* The length of each record, based on the characteristics of the data it contains.
* The sequence at the disposal of records within the file (storage structure can be sequential, indexed or relative).
Not all systems require the design of all the files, since most of them can use the old system and only need to link the new system to the master file where the records.
Design Interactions Database
Most information systems are already deployed in computing systems large or small, use a database that may include various applications, for this reason these systems use or database administrator, in this case the designer builds the database but consult your manager to agree on the use of this in the system.
Tools for System Design
Support the process of formulating the characteristics that the system must have to meet the needs identified during analysis activities:
Specification Tools
Support the process of developing the features that must have an application, such as inputs, outputs, process and control specifications. Many include tools for creating data specifications.
Presentation Tools
They are used to describe the position of data, messages and headers on terminal screens, reports and other means of entry and exit.
Development Tools Systems
These tools help us as analysts to translate designs into functional applications.
Software Engineering Tools
Support the process of making software design, including controls and procedures and documentation.
Code generators
Produce the source code and applications from the functional specifications articulated.
Tools for testing
Support the assessment phase of a system or parts of it against the specification. Include facilities for examining the proper operation of the system and the degree of perfection achieved in comparison with expectations.
The revolution in data processing in a computer, along with sophisticated design practices are dramatically changing the way we move from design specifications d Functional Information Systems.
Analysis Decision Support Systems semistructured
Methods Available
To obtain good results in decision support systems structured, we divide the work as it says above analysis system we are talking about, take into account:
1. If it is analytic or heuristic
2. How are the decisions taken in the three phases of problem solving intelligence
3. The use of multicriteria methods useful in solving semistructured problems.
These systems can operate in different ways ie, organizing information for decision situations, interaction with decision makers who carry the expansion in decision making, how to present information for better understanding by adding models and multiple criteria.
Where multiple criteria models include engagement processes, methods and weighted sequential elimination methods are best suited for managing complexity and semistructured nature.
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