What constitutes a good DBMS application design?
Database design is the process of producing a detailed data model of database. This data model contains all the needed logical and physical design choices and physical storage parameters needed to generate a design in a data definition language, which can then be used to create a database. A fully attributed data model contains detailed attributes for each entity.
The term database design can be used to describe many different parts of the design of an overall database system. Principally, and most correctly, it can be thought of as the logical design of the base data structures used to store the data. In the relational model these are the tables and views. In an object database the entities and relationships map directly to object classes and named relationships. However, the term database design could also be used to apply to the overall process of designing, not just the base data structures, but also the forms and queries used as part of the overall database application within the database management system (DBMS).
The process of doing database design generally consists of a number of steps which will be carried out by the database designer. Usually, the designer must:
• Determine the data to be stored in the database.
• Determine the relationships between the different data elements.
• Superimpose a logical structure upon the data on the basis of these relationships.
Within the relational model the final step above can generally be broken down into two further steps, that of determining the grouping of information within the system, generally determining what are the basic objects about which information is being stored, and then determining the relationships between these groups of information, or objects. This step is not necessary with an Object database.
In a majority of cases, a person who is doing the design of a database is a person with expertise in the area of database design, rather than expertise in the domain from which the data to be stored is drawn e.g. financial information, biological information etc. Therefore, the data to be stored in the database must be determined in cooperation with a person who does have expertise in that domain, and who is aware of what data must be stored within the system.
This process is one which is generally considered part of requirements analysis, and requires skill on the part of the database designer to elicit the needed information from those with the domain knowledge. This is because those with the necessary domain knowledge frequently cannot express clearly what their system requirements for the database are as they are unaccustomed to thinking in terms of the discrete data elements which must be stored. Data to be stored can be determined by Requirement Specification.
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Once a database designer is aware of the data which is to be stored within the database, they must then determine where dependency is within the data. Sometimes when data is changed you can be changing other data that is not visible. For example, in a list of names and addresses, assuming a situation where multiple people can have the same address, but one person cannot have more than one address, the address is dependent upon the name. When provided a name and the list the address can be uniquely determined; however, the inverse does not hold - when given an address and the list, a name cannot be uniquely determined because multiple people can reside at an address. Because an address is determined by a name, an address is considered dependent on a name.
(NOTE: A common misconception is that the relational model is so called because of the stating of relationships between data elements therein. This is not true. The relational model is so named because it is based upon the mathematical structures known as relations.)
What is software? How is software categorized?
The instructions that tell a computer how to carry out a task are referred to as a computer program. These programs form the software that prepares a computer to do a specific task, such as document production, photo editing, virus protection, file management, or Web browsing.
COMPUTER SOFTWARE determines the tasks a computer can help you accomplish.
Computer software, or simply software, is that part of a computer system that consists of encoded information or computer instructions, in contrast to the physical hardware from which the system is built.
The majority of software is written in high-level programming languages that are easier and more efficient for programmers, meaning closer to a natural language. High-level languages are translated into machine language using a compiler or an interpreter or a combination of the two. Software may also be written in a low-level assembly language, essentially, a vaguely mnemonic representation of a machine language using a natural language alphabet, which is translated into machine language using an assembler.
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The term "software" was first proposed by Alan Turing and used in this sense by John W. Tukey in 1957. In computer science and software engineering, computer software is all information processed by computer systems, programs and data.
Broad categories
The two main categories are system software and application software.System software is designed for computer-centric tasks, whereas application software is designed to help people accomplish real-world tasks.
For example, you would use system software to diagnose a problem with your hard disk drive or Internet connection, but you would use application software to edit a photo or write a term paper.
Computer software can be put into categories based on common function, type, or field of use. There are three broad classifications:
• Application software is the general designation of computer programs for performing tasks. Application software may be general purpose (word processing, web browsers,...) or have a specific purpose (accounting, truck scheduling, ..) Application software contrast with system software.
• System software is a generic term referring to the computer programs used to start and run computer systems including diverse application software and networks.
• Computer programming tools, such as compilers and linker, are used to translate and combine computer program source code and libraries into executable RAMs (programs that will belong to one of the three said)
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