Role Of A High-Level Data Model In The Database Design Process Free Writing Sample

Discuss the role of a high-level data model in the database design process. High-level data models assist in conceptual design and helps express data requirements of the users and includes detailed descriptions of the entity types, relationships, and constraints. The high-level data model is also used as a reference to ensure that all users’ data requirements are met and that the requirements do not include conflicts.

List the various cases where use of a null value would be appropriate. Null value would be appropriate when a particular entity does not have an applicable value for an attribute. There are two cases for such situations. The first case arises when it is known that the attribute value exists but is missing. An example for cases like such would be if the Height attribute of a person is listed as null. The second case arises when it is not known whether the attribute value exists. An example would be is the HomePhone attribute of a person is null.

Define the following terms: entity, attribute, attribute value, relationship instance, composite attribute, multivalued attribute, derived attribute, complex attribute, key attribute, value set (domain). Entity Entity is a “thing” in the real world with an independent existence. It can also be an object with physical existence (i. e. person, car) or conceptual existence (i. e. company, job). Attribute An attribute is a particular property that describes entity (i. e. person name company name). Attribute Value Attribute values are major data stored in the database. Relationship Instance Relationship Instance is an association of entities, where the association includes exactly one entity from each participating entity type. Composite Attribute Composite attribute is an attribute that can be divided into meaningful components.

Multivalued Attribute Multivalued attribute is an attribute that can have many values. Derived Attribute Derived attribute is an attribute whose value is computed from another attribute or combination of attributes. Complex Attribute Complex attribute is composite and multivalued attributes nested in an arbitrary manner. Key Attribute Key attribute is an attribute whose values are distinct for each individual entity in the collection. Value Set (Domain) Value set specifies the set of values that may be assigned to that attribute for each individual entry.

What is an entity type? What is an entity set? Explain the differences among an entity, an entity type, and entity set. Entity type defines a collection of entities that have the same attributes. Entity set is a named collection of related data. The differences between entity, an entity type, and entity set are:

  • Entity is a person, place, thing, event, or even a concept. It may be tangible or intangible. Examples of an entity are employees,
  • Entity type describes the schema or intension for a set of entities that share the same structure.
  • Entity set is the extension of the entity type.

Explain the difference between an attribute and a value set. An attribute is a particular property that describes entity. A value set specifies the set of values that may be assigned to that attribute for each individual entry. An example of an attribute is EmployeeAge and we can set the value set for this attribute to a range of integer numbers.

What is a relationship type? Explain the differences among a relationship instance, a relationship type, and a relationship set. Relationship type is the nature of a relationship between entities, expressed by the number of their possible occurrences in the related tables. The differences between a relationship instance, a relationship type, and a relationship set are:

  • Relationship instance is an association of entities, where the association includes exactly one entity from each participating entity type.
  • Relationship type defines a relationship set among entities from these types.
  • Relationship set is a set of associations.

What is a participation role? When is it necessary to use role name in the description of relationship type? Participation role is the part that each entity participates in a relationship. It is necessary to use role name in the description of relationship type when the same entity type participates more than once in a relationship type in different roles. In other words, role names are necessary in recursive relationships.

Describe two alternatives for specifying structural constraints on relationship types. What are the advantages of each. Two alternatives for specifying structural constraints on relationship types are cardinality ratio and participation. Cardinality ratio for a binary relationship specifies the number of relationship instances that an entity can participate in. The participation constraint specifies whether the existence of an entity depends on its being related to another entity via the relationship type.

Under what conditions can an attribute of a binary relationship type be migrated to become an attribute of one of the participating entity type? An attribute of a binary relationship type can be migrated to become an attribute of one the participating entity type when the relationship type is 1:1 or 1:N. This is because each entity participates in at most one relationship instance. However, for 1:N relationship type, a relationship attribute can be migrated only to the entity type at the N-side of the relationship.

When we think of relationships as attributes, what are the value sets of these attributes? What class of data models is based on this concept? The value sets of these attributes 11. What is meant by a recursive relationship type? Give some examples of recursive relationship types. A recursive relationship type exists if an entity can be related to itself or in other words, the same entity type participates more than once in a relationship type in different roles.

An example of a recursive relationship type is courses that require one or more other courses as prerequisites. The course entity is related to another course entity. In this case, the recursive relationship “course is a prerequisite to course” also happens to be a M:N relationship. This is because a course can have more than one prerequisite, and a course can be a prerequisite to many other courses. Another example of a recursive relationship type is in a supervision relationship type between an employee and a supervisor. Both entities are members of the same Employee entity type. In this example, the employee entity type participates twice in the supervision relationships, once in the role of a supervisor, and once in the role of supervisee.

When is the concept of weak entity used in data modeling? Define the terms owner entity type, weak entity type, identifying relationship type, and partial key. The concept of weak entity is used in data modeling when there are many attributes or when entity types do not have key attributes of their own. Owner Entity Type Owner entity type is an entity type that is related to weak entity types through combination of some of their attribute values.

Weak Entity Type Weak entity type is an entity type that does not have key attributes of their own. Identifying Relationship Type Identifying relationship type is the relationship type that relates a weak entity type to its owner. Partial Key Partial key is a set of attributes that can uniquely identify weak entities that are related to the same owner entity.

Can an identifying relationship of a weak entity type be of a degree greater than two? Give examples to illustrate your answer. An identifying relationship of a weak entity type can be of a degree greater than two. For a ternary identifying relationship type, the weak entity type has several owner entity types. An example for a ternary relationship such as Supply must be represented as weak entity type, with no partial key and with three identifying relationships. These participating entity types Supplier, Part, and Project are together the owner entity types. Hence, an entity in the weak entity type Supply is identified by the combination of its three owner entities from Supplier, Part, and Project.

Discuss the convention for displaying an ER schema as an ER diagram. Entity types are shown in rectangular boxes. Relationship types are shown in diamond-shaped boxes attached to the participating entity types with straight lines. Attributes are shown in ovals, and each attribute is attached by a straight line to its entity type or relationship type. Component attributes of a composite attribute are attached to the oval representing the composite attribute. Multivalued attributes are shown in double ovals and key attributes have their names underlined. Derived attributes are shown in dotted ovals.

Weak entity types are distinguished by being placed in double rectangles and by having their identifying relationship placed in double diamonds. The partial key of the weak entity type is underlined with a dotted line. The cardinality ratio of each binary relationship type is specified by 7attaching a 1, M, or N on each participating edge. The participation constraint is specified by a single line for partial participation and by double lines for total participation. We show the role names when one entity type plays both roles in a relationship.

Tony Hsieh Contemporary Leader

Tony Hsieh, CEO, Zappos. com Zappos is an online shoe and merchandise retailer that grew from a startup company in a San Francisco apartment to become a billion dollar company within a decade, while also being consistently ranked as one of the top companies to work for the past five (5) years. Zappos has 1,243 employees and had revenue of $2. 2 billion in 2011. While the company cut 1,670 jobs in 2011, there was no voluntary turnover and more than 46,000 job applicants. (Vellota, 2013) This was accomplished by making good business decisions and adhering to a set of core values that everyone is expected to commit to.

Amazon acquired Zappos in 2009 for $920 million, yet, it continues to operate independently to maintain their unique culture under the leadership of Chief Executive Officer (CEO), Tony Hsieh. The evolution of the Zappos brand promise over the years has been follows: 1999 – Largest selection of shoes; 2003 – Customer Service; 2005 – Culture and Core Values as the Platform; 2007 – Personal Emotional Connections; 2009 – Delivering Happiness. (Hsieh, 2010) Zappos is currently located in Henderson, Las Vegas and in the fall of 2013, they will be relocating to the downtown Las Vegas area.

This downtown area is undergoing an urban revitalization movement and is being transformed into “the most community-focused large city in the world. ” (Kaydo, 2013) Visitors can arrange online for a free tour of Zappos’ headquarters that include transportation at no cost. Zappos has a library with an impressive list of titles that everyone is encouraged to check out free of charge to “Pursue Growth & Learning”. Zappos Insights was created to mentor companies and individuals and give them the chance to immerse themselves in the Zappos Family culture. Hsieh, 2010) Tony Hsieh was born in Illinois, the oldest of three boys. His parents emigrated from Taiwan as college students. Later, the Hsieh family relocated to the San Francisco Bay area in California. Growing up, his parents placed emphasis on mastering musical instruments and academic and career accomplishments. At a young age, Tony fantasized about making money. In elementary school, he held garage sales; invested his time and money in an earthworm farm; sold advertising space in a self-composed newsletter; and in middle school started a mail order photo button enterprise that earned him $200 a month. Hsieh, 2010) He got the idea for the photo button by reading the classified section of Boys Life magazine. He handed off his lucrative button business to his younger brother when he went off to college at Harvard University where he studied computer science. In college, Tony won a bid to run the college grille, which he invested in an oven and sold pizzas to student residents. It was at Harvard; Tony met Alfred Lin, who unbeknownst to Hsieh was making a greater profit from Tony’s pizzas by selling them by the slice.

Tony’s goal after graduating college was to land a high paying job “that did not seem like too much work”. (Hsieh, 2010) Before graduating from college in 1995, Oracle offered Tony a job as a software engineer, which he accepted because it paid the most money, and for his moving and housing expenses during their three-week training program. Tony soon became bored and approached his former college roommate and Oracle colleague, Sanjay Madan, with the idea of creating websites for businesses in their spare time. Soon after, they both quit their jobs at Oracle and devoted their full time to this endeavor.

In 1998, Tony Hsieh, at the age of twenty-four (24) years, sold the company he co-founded, with Sanjay Madan, called Link Exchange, two years and eight months earlier, to Microsoft for the sum of $265,000,000. (Reiss, 2010) Link Exchange was an internet advertising company that displayed banner advertisements on their website. With the profits from the sale of Link Exchange, Hsieh co-founded, with another college alumnus, Alfred Lin, an investment company called Venture Frogs. Venture Frogs invested in a variety of tech and internet startup companies. Hsieh, 2010) In 1999, Nick Swinmurn was walking around a mall in San Francisco looking to purchase a pair of shoes. He went home empty-handed after walking from store to store. He tried looking for shoes online and was unsuccessful. He found a number of small stores selling shoes online; however, there was no major online retailer than specialized in shoes. Nick decided to quit his job and start an online shoe retail business. His idea was to create a website that offered a large selection of shoe brands, styles, sizes and widths. He called it shoerite. om. Swinmurn arranged a meeting with Tony Hsieh and Alfred Lin, investors who owned Venture Frogs, and pitched his idea. Hsieh was intrigued by Swinmurn’s statistic of “footwear in the United States is a $40 billion market, and 5% of that market was already being sold by paper mail order catalogs. ” (Hsieh, 2010) Since, Nick knew little about buying shoes, except for his own personal use, and not a thing about selling them, Hsieh sent him away in search of two things; someone who know about buying and selling shoes and a better name.

Nick returned with Fred Mossler, who worked in the shoe department at Nordstrom’s, and a name, Zappos. com. Zappos was derived from the Spanish word, zapato, which means “shoe”. Hsieh was taken by Nick and Fred’s passion, took a “leap” of fate, and decided to invest in them. Two months later, in 2000, Tony Hsieh joined Zappos as their Chief Executive Officer (CEO). (Harnish, 2012) Alfred Lin joined as Chief Operating Office and Chief Financial Officer (COO/CFO) in 2005. Zappos. com profits went from $0 in 1999 to more than $920 million in 2009 when the company was sold to Amazon. om. (Hsieh, 2010) Zappos’ success is largely attributable to its unique focus on customer service; however, Tony Hsieh’s primary focus and top priority is company culture. (King, 2011) It is Hsieh’s philosophy that if they “got the culture right, then building our brand to be about the best customer service would happen naturally on its own. ” (Hsieh, 2010) On the topic of customer service, Hsieh believes that “customer service shouldn’t be just a department. It should be the entire company. (King, 2011) Zappos defines the core values from which they develop their culture, their brand, and their business strategies. The ten core values that Zappos live by are: (Hsieh, 2010) 1. Deliver WOW through service – doing something that is beyond what is expected and that has an emotional impact on the receiver. 2. Embrace and Drive Change – embracing change enthusiastically and perhaps even more importantly, to encourage and drive it. 3. Create Fun and A Little Weirdness – encouraging weirdness is to encourage people to think outside the box and be more innovative.

When you combine a little weirdness with making sure everyone is also having fun at work, it ends up being a win-win for everyone. Zappos employees are more engaged in the work that they do and the company as a whole becomes more innovative. 4. Be Adventurous, Creative, and Open-Minded – wanting people to develop and improve their decision-making skills. Zappos encourages people to make mistakes as long as they learn from them. 5. Pursue Growth and Learning – inside every employee is more potential than even the employee himself/herself realizes.

Zappos’ goal is to help employees unlock that potential. However, it has to be a joint effort: you have to want to challenge and stretch yourself in order for it to happen. 6. Build Open and Honest Relationships with Communication – strong, positive relationships that are open and honest are a big part of what differentiates Zappos from most other companies. Strong relationships allow them to accomplish much more than they would be able to otherwise. 7. Build a Positive Team and Family Spirit – Zappos employees are more than just a team; they are a family.

They watch out for each other, care for each other, and go above and beyond for each other because they believe in each other and they trust each other. They work together, but they also play together. Their bonds go far beyond the typical “co-worker” relationships found at most other companies. 8. Do More With Less – Zappos employees are focused and serious about the operations of the business. They believe in working hard and putting in the extra effort to get things done. 9. Be Passionate and Determined – Passion and determination are contagious.

At Zappos, they believe in having a positive and optimistic (but realistic) attitude about everything they do because they realize that this inspires others to have the same attitude. 10. Be Humble – Zappos believes that no matter what happens they should always be respectful of everyone. (Hsieh, 2010) Tony Hsieh believes that these are “committable” core values independent of actual job performance and “that you are willing to hire and fire based on them. ” (Heath, 2010) He believes in hiring people with personality traits in line with these core values for a good “cultural fit”. Robin, 2011) Hsieh believes a very different form of corporate culture is a model for achieving success and how concentrating on happiness of those around you, you can dramatically increase your own. Influence requires listening and relationship building with a win-win outcome. According to Hsieh, “If your business style is still focused on the ‘old school’ hard-selling, push-marketing approach, it’s time to take a close look at how well it is servicing you these days. The new culture driven by social media is all about forging real connections and building relationships. (Zwilling, 2012) When it comes to the topic of leadership, Hsieh “cringes at the word ‘leader’. It is more about getting people to do what they are passionate about and putting them in the right context or setting. They’re the ones doing the hard work. ” (Groth, 2012) Zappos corporate structure is flat where decision-making is decentralized and the employs are more empowered to make decisions. Entrepreneurs, leaders and managers in any field can learn a lot about hiring, leadership, employee engagement and business communication by studying Tony Hsieh business approach.

Employee or job satisfaction is related to positive customer outcomes and affects your bottom line. Satisfied employees increase customer satisfaction and loyalty. Zappos first core value of “Deliver WOW through service” is more about the way in which Zappos does it. Employees are encouraged to “create a little weirdness” and are given unusual discretion in making customers satisfied. Employees are encouraged to use their imaginations, including sending flowers to disgruntled customers and they even offer a $2,000 bribe to new employees to quit the company after training to weed out the half-hearted. Robbins, 2013) In summation, Tony Hsieh understands how organizational behavior affects a company’s performance. Employees are empowered to make decisions that increase customer satisfaction. At Zappos, employee loyalty, job satisfaction and productivity are high, contributing to the company’s growth. (Robbins, 2013) The Zappos environment gives employees the sense that they are part of something bigger. Hsieh feels inspiration is a more effective motivator than fear. Zappos is structured a lot less hierarchical than most companies and the decision making process in decentralized.

In selecting employees, his decision is significantly influenced by how well the candidates will fit into the organization and whose values are in line with the organization’s values. Tony Hsieh is very interested in making people happy as the title of his book “Delivering Happiness” suggests. Inspired leaders do not sell the obvious. Not only is Zappos more than just shoes (they increased their line to include jewelry, house wares, fragrances, skin care products, clothing and much more) so is Zappos’ CEO, Tony Hsieh. He is a good example for all entrepreneurs, leaders and managers to follow.

Bibliography Gallo, C. (2010). Business Renegade: Zappos’ Tony Hsieh. Forbes Magazine. Retrieved April 12, 2013, from http://www. forbes. com/sites/carminegallo/2011/11/01/business-renegade-zappos-tony-hsieh/ Groth, A. (2012, September 26). Zappos CEO Tony Hsieh Explains Why The Word ‘Leader’ Makes Him Cringe. Business Insider. Retrieved April 1, 2013, from http://www. businessinsider. com/zappos-ceo-tony-hsieh-on-leadership-2012-9 Harnish, V. (2012). The Greatest Business Decisions of All Time. New York: Fortune Books. Heath, T. (2010).

On Leadership: Zappos CEO Tony Hsieh on who he won’t hire. The Washington Post. Retrieved April 30, 2013, from http://www. washingtonpost. com/wp-dyn/content/video/2010/07/14/VI2010071401317. html Hsieh, T. (2010). Delivering Happiness: A path to profits, passion, and purpose. New York: Hachette Book Group. Kaydo, C. (2013, April 30). How Zappos CEO Tony Hsieh is Using Events to Transform Downtown Las Vegas. BizBash. Retrieved April 30, 2013, from http://www. bizbash. com/how-zappos-ceo-tony-hsieh-using-events-to-transform-downtown-las-vegas/las-vegas/story/26020#sthash. VmNplYPK. pbs King, R. (2011, September 29). Zappos CEO: Company culture is higher priority than customer. Between the Lines. Retrieved from http://www. zdnet. com/blog/btl/zappos-ceo-company-culture-is-higher-priority-than-customer-service/59245 Reiss, R. (2010, July 10). Tony Hsieh on his Secrets of Success: An Interview with the CEO pf Zappos. com. Forbes Magaizine. Retrieved March 22, 2013, from http://www. forbes. com/2010/07/01/tony-hsieh-zappos-leadership-managing-interview. html Robbins, T. A. (2013). Organizational Behavior. New Jersey: Pearson Education, Inc. Robin, M. B. (2011).

The Great Workplace: How to build it, how to keep and why it matters. San Francisco: Jossey-Bass. Torossian, R. (2011). For Immediate Release: Shape Minds, Build Brands and Deliver Results with Game-Changing Public Relations. Dallas: BenBella Books, Inc. Vellota, R. N. (2013, January 17). Zappos. com makes Fortune’s list of best places to work. Vegas Inc. Retrieved May 2, 2012, from http://www. vegasinc. com/news/2013/jan/17/zapposcom-makes-fortunes-list-best-places-work/#/0 Zwilling, M. (2012, December 25). Entrepreneurs Learn New Rules for Real Influence. Forbes Magazine. Retrieved April 25, 2013, from

Literary Analysis Of “Gravity”

Literary Analysis of “Gravity” by David Leavitt The following pages will consist of a literary analysis of the short story presented by the author David Leavitt, which is taken from his book “A Place I’ve Never Been” (Nguyen, 2006). “Gravity” narrates the story of a boy with AIDS, whose life is slowly consuming like the wax of a lit candle. The author presents the reader with the crudity of enduring such disease mainly from the patient’s and his mother’s perspective. The underlying intention of David Leavitt is to educate the reader about the fragility of life and how important it is to live it fully and well.

Its message is directed both to people who are undergoing some kind of disease and to people who are healthy since it represents the unpredictability of the future. “Theo had a choice between a drug that would save his sight and a drug that would keep him alive, so he chose not to go blind” is the first sentence of the story. When reading it for the first time, I was shocked to see that someone would prefer to live less while being able to see than to live more and be blind. When reading the story for the second time though, the reader can extract from this sentence the importance of living your life fully.

Theo chose quality over quantity. This first sentence also puts the reader into the perspective of a boy with AIDS, showing the kind of decisions AIDS patients may have to take. Decisions that are out of the ordinary and that no one would ever see themselves taking. The use of nouns such as “pills” and “injections” and adjectives such as “unpleasant” and “painful” already set the tone of a sad and gloomy reading. The reading continues with a flashback of Theo remembering himself and his mother Sylvia going to a show together in New York.

Back then, Theo’s eyesight was already bad, however, the author leaves it open for interpretation whether the boy was already infected with AIDS or not. Anyways, this passage also represents the pleasure that Theo went through when he was finally able to see well with his mother’s eccentric glasses. The author makes the reader feel the relief and the pleasure that Theo felt by using words such as “astonished”, “precision”, “sharp” and especially with the phrase “the world came into focus”. The short-sighted ones like me immediately feel represented by Theo and understand the sensation of being able to see well.

For the ones who have never seen the world through the eyes of a short-sighted person, this passage also serves as an explanation of why Theo chose to be able to see and live less over being blind and living more. Here, Theo’s mother is also introduced to the reader for the first time and an analogy is made between the flashback and the way she’d maneuver him around people who stared at him. Sylvia is one of the main characters of the short story and is presented as a woman who wears “harlequins with tiny rhinestones in the corners”.

She is also characterized as a caring mother who has experienced the darkness of watching her own mother dying. It is not specified in the text the reason why her mother died, but the reader can definitely sense that it did not happen from one day to another. Her mental calmness when administering the “sight-giving” medicine to his son also shows that Sylvia is a strong person who keeps fighting until the end of his Theo’s life while he, the protagonist of the story, seems to be hopeless.

The author shows this lack of hope when he says “his life, sometimes he thought”. The setting of a hospital also contributes to the feeling that all hope is gone but the most evident sign of despair is “the unswimmable gulf between him and the eve-receding shoreline of the well” Both Sylvia and Theo are round, complex characters that are unpredictable and capable of change. Due to the short length of the story though, the reader cannot yet tell whether the main characters remain static or become dynamic.

The next paragraphs of the story reveal some secondary characters such as Theo’s cousin Howard, who is having and engagement party in the future; Bibi, who I assume is Sylvia’s sister; and the two gentlemen that work in the shop where the next part of the plot takes action: Mr. Sherman and Mr. Baker. All these secondary characters are flat and most likely static. The reader can immediately feel the tension between Sylvia and Bibi through the words “shopping for revenge”. The apparent cause of this tension is a tacky graduation gift that Bibi gave to Theo some time ago; however there eems to be a bigger unresolved, long-lasting conflict between the two ladies that might have been accentuated by the paradox that while Theo is dying, his cousin is celebrating. The protagonist and his mom arrive in a shop in the search of a “something truly spectacular for Howard’s engagement” to “make Bibi blanch”. When the mother asks his son for advice, Theo’s response has a connotative interpretation. What he is really trying to convey is that Sylvie should not buy such a spectacular gift if her real intentions are to get Bibi back.

Once again, in this part of the story the author remarks the pessimistic approach that Theo has and contrasts it with the insatiable efforts of his mom trying to pretend that there is nothing wrong. When she says “You live and learn” he replies “You live” and she replies back “Well, look, here we are”. Touches of black humor makes the reader smile and then feel sorry when Theo says that the advantage to the situation is that they can park in handicapped places. It seems like Mr. Sherman and Mr.

Baker, workers of the gift shop, already knew Sylvie from previous visits. The dialogue held between mother and son in the shop and the way they treat the crystal bowl that she wants to buy for Howard, is a clear example of symbolism. The author uses the crystal bowl as a representation of life, being extremely valuable yet extremely fragile. Her tossing it to Theo like a football represents her persistent efforts to encourage his son to live longer and somehow her unwillingness to accept the critical situation they are both going through.

No matter how hard she tried to keep negative thoughts from her mind, it was obvious to Theo that the whole situation was secretly causing her some sort of internal damage. In conclusion, this short story is a gloomy narration of the last days of a terminal AIDS patient and his mother, who resists to give up on her efforts to make her son live to the fullest. The third person narrator puts the reader into the shoes of Theo and his mother, and makes us appreciate life and what is most important, being healthy.

The use of resources such as analogies, flashbacks and symbolism all contribute to the creation of a sad and intriguing plot. Furthermore, the words have been carefully picked to trigger certain sensations in the reader’s mind. The story concludes with an open ended doubt that makes the reader think about the deeper meaning of the actions of the characters. Reference Porter Shreve and B. Minh Nguyen, 2006. Gravity. In: 30/30 Thirty American Stories from the Last Thirty Years. New York: Penguin Academics, pp. 204-208.

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