Characteristics of a good database design

Characteristics of a good database design 1. Introduction The purpose of this report is to mainly discuss about characteristics of a good database design and a quality design. Main reasons behind writing this report is as part of implementation of Stanwell parish plan the need for a database application was identified by several committees. Our committee is responsible for the design a database for record the runners participated on the annual Fell race. The new broadband internet access facility is helpful in creating these new facilities. A database can be identified as a set of records or files which are logically related. Computer based databases are normally organised as one or multiple number of tables. A table consists of series of rows and columns. Relational model is a powerful and commonly used method for organising data. The table design of the database reflects the quality of the database. The principles of normalization need to be considered always when designing a effective database. Objectives of normalization are follows. Minimising data redundancy Minimising data restructuring Minimising I/O by redesign transaction sizes Enforcing referencing integrity. When designing an effective database following techniques and concepts are important to consider. Identifying an entity as a logical collection of items related to the stated database. And an attribute is a descriptive or quantitative characteristic of the entity. The physical counterpart of the entity is a database table and the physical counterpart of the attribute is the column. Primary key is identified as an attribute which identifies each instance of an entity uniquely. The logical link between two entities is the relationship. When the primary key of a parent entity exists in a child entity, it is called as a foreign key. There are two types of relationships, Identifying and non Identifying. Identifying relationships are when primary key of the parent entity exists in the primary key of the child entity. In non identifying relationships primary key of the parent key exists in the child entity but not as a part of primary key of the child entity. To understand the nature of the relationship between the parent and child entities, cardinality is helpful. Four types of cardinalities are  § 1 to 0 or more  § 1 to 1 or more  § 1 to 0 or 1  § 1 to many In designing a correct database ER, EER and Use Case are really useful modelling tools. 2. Importance of data modelling Data model is a very useful tool in communicating between developers and users of a database. It is also helpful in identifying design issues and other problems before starting the actual design process. A data model is like a blueprint of a newly constructing building. Builders will newer start building a large construction without a proper blueprint. Even though changes are made during the developing process, the basic foundation remains the same. Importance of ER diagrams in the design ER diagrams falls into a category of data modelling.ER diagrams show entities in a database and relationships between tables. This graphical representation helps to understand how the database works with the interactions and dataflow. No matter how large or small the database is, the concepts of entity and relationship are the same. ER diagrams have 3 basic components. Entities Attributes Relationships For an example, in the Fell Race database, Race can be identified as an entity and year of the Race can be identified as an attribute. An entity corresponds to a table of the database and attributes corresponds to the columns of that particular table. Most common errors that can happen when designing an ER diagram can be stated as, Missing constrains Missing keys to any entity type Unexpressed constrains due to bad design Associating attributes with wrong entry types Putting invalid constrains Misuse of subclasses Using foreign keys instead of relationships EER Diagrams in modelling EER diagrams are also a similar kind of tool to ER diagrams except for some little differences. It is identified as enhanced model of ER diagrams. EER = ER + hierarchical relationships Hierarchical relationship means relationship between Super class and subclass, the IS A relationship. The next step is transferring the ER diagram or EER diagram into well structured relations. A relational table is made up of one or more data tables or relations. The mapping should be done in a way to avoid data duplication. This is called data redundancy. Data redundancy can become a problem for several reasons. Entering same data over and over again is a waste of time. Data redundancy increases the probability of occurring errors Errors can occur when retrieving data. Disk space is wasted. Affect the performance of the overall system When updating, deleting data, multiple rows should be considered. Normalization is the process used to avoid data redundancy. Importance of Use Case diagrams in the design Use cases are used in the analysis stage of the design process. Main target of drawing a use case is to identify the system functionality. Use cases separate the system into use cases and actors. Use cases represent the integration of actors and the system. An actor is defined as a thing with behaviour. An actor could be a person or another system. According to the Fell Race system actor can be someone who uses the system to enter data (user). 3. Importance of a good database design Mainly a good, effective database design helps the development team to reduce the costs and time taken for the overall development. By creating a good data model and following the correct process, helps the development team to understand user requirements clearly and accurately. 4. Is a correct database design necessarily a quality design? The answer is no. A correct database design is not always a quality design. But a quality design should always be a correct design. In a quality design, instead of putting data over multiple files, data is stored in a single logical unit. This reduces the duplication of data. The non duplication of data helps to maintain data integrity. Also a quality design is helpful in maintain the security of data. Data can be managed properly trough a quality database design. Finally a quality design is a design that helps to increase the performance of the database. A correct database design would work, but a quality design will help increase the performance of the database. 5. Conclusion An affective and quality database design helps the development team to reduce time and the overall cost of the system development process. By taking a correct approach to database design helps the team to understand the user requirements correctly and deliver a system the user desires. A good database design will also help increase the overall performance of the system. References Mike gahan.2000.An introduction to databases.[online](updated 10 October 2000) Available at: http://www.ucl.ac.uk/archaeology/cisp/database/manual/node1.html [Accessed 10 January 2010]. SQLTeam.com.2000.Database design and modelling fundamentals.[online](updated 30 June 2000) Available at : http://www.sqlteam.com/article/database-design-and-modeling-fundamentals [Accessed 10 January 2010]. Farrkoh Alemi.2007.healthcare databases.[online](updated 27 November 2007) Available at : http://gunston.gmu.edu/709/DataModelingERDiagram.asp [Accessed 12 January 2010] Development cycles.2004.Entity Relationship Modeling-Experience vs InExperience.[online](updated 05 April 2004) Available at : http://www.devarticles.com/c/a/Development-Cycles/Entity-Relationship-Modeling/13/ [Accessed 12 January 2010] Veda c storey. Modelling quality requirements in conceptual database design.[e-book] Available at : http://web.mit.edu/tdqm/www/tdqmpub/QEROct98.pdf [Accessed 12 January 2010] John A. Hoxmeier.1997.A framework for accessing database quality.[online]Available at : http://osm7.cs.byu.edu/ER97/workshop4/jh.html [Accessed 12 January 2010]

origins of the american traditions :: essays research papers

The origins of the traditions held by the population of American started from the time that this land was first set foot on by the human species and was compounded throughout the rest of time. The immigrants, and slaves expanded up on the traditions of the original settlers. And along with those they brought their own religions and cultures that also added to the traditions of this country.   Ã‚  Ã‚  Ã‚  Ã‚  Long before the Europeans ever set foot on to the fair soil, people from Asia came to the land that now makes up the Americans. They came by crossing the land and ice bridge once located across the Bering Strait between the Alaska and Russia. This location is now submerged by water. The exact date of the first human arrivals in America is unknown but estimated to be range from twenty thousand to fifty thousand years ago. The Asians that made the trip across the land bridge are the predecessors of the Native Americans that were located in the Americas as the Europeans began to arrive. If the features are compared between these two the similarities are striking and the facts behind this theory become ever more prevalent.   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  The Native Americans that were Descendants of the Asian populated North, Central, and South America creating a large variety of cultures. In the late fifteenth century, there were perhaps 240 distinct Native American cultures just in North America alone with a population estimated at between one to two million people. Although these two million people varied greatly in there social cultures, government, economic systems, and others aspects of their life, they shared between them a common respect for and connection with the natural world. Were as the Europeans encroaching upon their land tended only to look at the natural world as something to be subdues owned and used for personal gain.   Ã‚  Ã‚  Ã‚  Ã‚  The First Europeans to arrive in America are believed to be Norse sailors from Scandinavia. Leif Ericsson, son of Eric the red who settled Greenland, established a brief settlement in current day Canada around the year one thousand. After this brief settlement the Europeans did not return for nearly five hundred years on a misguided voyage not in tended for the Americas but for the Orient. This discovery was made by the Italian Explorer Christopher Columbus, who had the misconception that he had reached India when he had made land fall on the present-day island of th4e Bahamas, henceforth the natives whom he met being called â€Å"Indians†.

London Poems Essay

Wordsworth and Blake each use language in different ways to present their own view of ondon. They both reveal their feelings through their viewpoint, the way they have structured their poems and the poetic devices each of them use. Wordsworth wrote his ‘On Westminster Bridge’ on September 3rd 1802 as a result of him riding a stage coach over Westminster Bridge. Wordsworth’s view of London from Westminster Bridge is from a fair distance away because he doesn’t describe the ground level in much detail, nor does he describe people with much detail. His view of London is quite broad, â€Å"Dear God! The very houses seem asleep†. Aswell as being far away, he is also situated quite high up to get this broad view that he describes. The time of day in which the poem is set is early morning. He mentions the air being smokeless, â€Å"..in the smokeless air†. His poem suggests that he thought that London was usually a horrible,dirty and mucky place. But when he sees London’s air clear and clean, â€Å"Ne’er saw I, never felt a calm so deep!† This shows he doesn’t visit London very often. Wordsworth’s peom focuses more on the general look of London. He is more concerned with buildings and atmosphere of london rather than the details of people and their lives. ‘On Westminster Bridge’ is written in the form of a sonnet. He tells us about what he can see, â€Å"..ships, towers, domes, theatres and temples..†. His feelings at the start of the poem are more overtly shown, but the farther you read into the poem, his feelings become more apparent.The last six lines or seset shows his feelings about London and how is opinion has changed from his original view of London, â€Å"Dear God!†. He is suprised how differnt London can look. In addition, William Wordsworth uses various poetic devices to make his sonnet have more depth and feeling and to create a picture in the readers mind of how London used to be in his eyes. He uses similes, â€Å"The city now doth, like a garment†. He is trying to make it easier for the reader to create an image in their head by saying one thing is like another. The poem also has personification included, â€Å"The river glideth at his own sweet will†, â€Å"The very houses seem asleep†. One other example is â€Å"The sun in his first splendour†. The personification that he uses gives the pictures in your head some animation by saying that they have human characteristics. Wordsworth also uses symbolism, â€Å"And all that the mighty heart is lying still†. All these methods are each in turn creating images in the reader’s head. Overall, Wordsworth’s poem is a more general view with a change in his point of view within the poem. Blake on the otherhand writes from a very different point of view. he form os his peom differs from Wordsworths. Blake focuses on the people in the city and they are like. Blake’s view is from ground level so includes a lot more detail. Because Blake’s view is much closer than Wordsworth’s, Blake’s view point is much narrower. Blake takes a much closer look at peoples lives and he thinks that this is the key to what London is all about, the people. Blake generally employs different peotic devices from Wrodsworth’s to put across his point of view on London. Blake uses repetition to emphasize his view on London and to try and make it look as if everyone is the same. It also has some metaphors too, â€Å"Mind-forged manacles† and â€Å"..plagues the marriage hearse†. The Blake poem uses hyperbole to criticize London and the sadness and malice of the people who live their. Blake’s London brutally painted is a dark, dirty, disease ridden and deprived place. Unlike the Wordsworth poem, it leaves you in no doubt as to the authors feelings on the subject. Blake’s poem conveys his feelings in a more abstract style, when he uses the people and buildings of London to represent the institutions which they are associated with. He uses the image of a church to criticise religious establishments and a palace to signify the state, and authorities who control it. He gives the image of the â€Å"Soldier’s sigh running in blood down palace-walls†. Here he is attacking the monarchy and government for condemning young men to death by sending them off to fight in foreign wars. Wordsworth and Blake each have different views on London. Wordsworth shows how nice,warm and calm London can look in the early morning, proving people wrong that its not always grimy and dirty. However Blake’s poem is more against London, trying to prove that it makes people miserable and that everyone feels the same way. Both these poems, in my opinion, share feelings of concern and disgust for London. If i had to pick which one I prefered I would choose the Blake poem. This is because the meaning of the words is more clearcut. I accept the point of view of Wordsworth, how it can be clean and not always dirty and horrible as some may think.

The Political System Of The United States - 2164 Words

Extended Essay Rough Draft The political system of the United States of America is based upon democratic and republican principles, giving birth to the representative democracy that is our government today. Over the many years since the founding of the nation and our first president, George Washington, politics has separated itself into factions, more commonly called parties, based on common and shared beliefs, religion, and ideals. The development of these parties has encouraged corruption to run rampant throughout the government, and this corruption has lead to a decrease in efficiency and effectiveness in the government as well. Parties have become increasingly polarized as well, drawing closer to the extremes rather than a more moderate, common ground. This increased polarization has created an almost unbreachable ideological gap within the members of congress, and any sort of collaboration has been made impossible by this new trend of loyal opposition, the opposition of one bill or piece of legislature s imply because the other party drafted it. This begs the question of the genesis of such a divide, and from this inquiry it is discovered that there have been three major contributions to this party polarization: redistricting methods, also known as gerrymandering, the development of super PACs, and slanted Supreme Court decisions. This investigation will explore the ways in which and the extent that redistricting methods, super PACs, and Supreme Court decisions haveShow MoreRelatedThe United States Political System935 Words   |  4 PagesThe United States political system is dominated by an intense battle for power. Those who have control, have the ability to influence the way our nation is operated. 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