Chapter 3 Effects of IT on Strategy and Competition

Report
Chapter 5
Database Processing
- Case & Exercise
Jason C. H. Chen, Ph.D.
Professor of MIS
School of Business
Gonzaga University
Spokane, WA 99258 USA
[email protected]
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In-class exercise
UYK (p.171)
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1.Draw an entity-relationship diagram that shows the
relationships among a database, database
applications, and users.
User
(e.g., GU
students,
faculty, staff
etc.)
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mandatory many
mandatory one
Database
Application
Database
(e.g., ZagWeb,
Blackboard,
Bookstore,
Library, etc.)
(e.g., GU
database)
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2.Consider the relationship between Adviser and Student in Figure 5-20.
Explain what it means if the maximum cardinality of this relationship is
(A:S – Advisor:Student)
• a. N:1
– An advisor is assigned one student; a student is assigned many advisors.
• b. 1:1
– An advisor is assigned one student; a student is assigned one advisor
• c.
5:1
– An advisor is assigned one student; a student is assigned no more than
five advisors
• d. 1:5
– An advisor is assigned no more than five students; a student is assigned
one advisor
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3. Identify two entities in the data entry form in Figure 527. What attributes are shown for each? What do you
think are the identifiers?
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Fig 5-27 Sample Data Entry Form
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3. Identify two entities in the data entry form in Figure 5-27. What
attributes are shown for each? What do you think are the
identifiers?
• Entities (or Tables/Files):
– Employee; Class
• Employee attributes:
– Employee Number, First Name,
Last Name, Email
• Class attributes:
– Course Name, Course Date,
Instructor, Remarks
• Employee identifier (key):
– Employee Number
• Class identifier (key):
– Course Name & Course Date
– Why two fields? And what is it
called?
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4. Using your answer to question 3, draw an E-R diagram for
the data entry form in Figure 5-27. Specify cardinalities. State
your assumptions.
Employees take zero or more classes; a class is taken by one
or more employees
Assumptions:
1. Courses may be offered many times but always on different
dates.
2. Employees may not have taken any classes.
3. Classes have at least one employee.
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• 5. The partial E-R diagram in Figure 5-28 (next
page) is for a sales order. Assume there is only
one Salesperson per SalesOrder.
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a. Specify the maximum cardinalities for each relationship. State your
assumptions, if necessary.
• A Salesperson writes many Sales Orders; a Sales Order is written by one
Salesperson. (Assumes Salespeople work alone and not in teams)
• A Customer places many Sales Orders; a Sales Order is placed by one
Customer.
• A Sales Order contains many Line Items; a Line Item is contained in one
Sales Order.
• A Line Item contains one Item; an Item is contained in one Line Item.
[M]
[M]
[M]
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b. Specify the minimum cardinalities for each relationship. State your assumptions, if
necessary.
• A Salesperson may have zero Sales Orders; a Sales Order is written by one Salesperson.
(Assumes Salespeople work alone and not in teams; assumes a Sales Order is not
required for a Salesperson to exist in the system)
• A Customer places at least one Sales Order; a Sales Order is placed by one and only one
Customer. (Assumes at least one Sales Order is required for a Customer to exist in the
system)
• A Sales Order contains at least one Line-Item; a Line-Item is contained in one and only
one Sales Order.
• A Line Item contains one and only one Item; an Item is contained in one and only one
Line Item.
[0]
[>=1]
[>=1]
[1]
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Case Study 5: Fail Away with Dynamo,
Bigtable, and Cassandra (1 – 5, p.174)
• Current relational DBMS products not
designed for large, multi-server systems
• NoSQL databases – Dynamo, Bigtable,
Cassandra
• Amazon: Dynamo
• Google: Bigtable processes petabytes of data
on hundreds of thousands of servers
• Elastic
• Cassandra used by Facebook, Twitter, Digg,
Reddit
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1. Clearly, Dynamo, Bigtable, and Cassandra are critical technology to
the companies that create them. Why did they allow their employees to
publish academic papers about them? Why did they not keep them as
proprietary secrets?
•
• The companies that originally developed Dynamo, Bigtable,
and Cassandra did so to solve a real business problem they
encountered as they went about doing their primary business.
They were not in the business of developing, marketing, selling
and supporting a new method of storing data.
• Since the data store they developed was not a focus of their
business strategy, but was a means to accomplish their business
strategy, they did not feel that it was worth it to try to keep the
data store a proprietary secret. They were perhaps also aware
that others were working on similar solutions and so did not feel
that any competitive advantage they gained from their solutions
would be sustainable over time.
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2. What do you think this movement means to the existing DBMS
vendors? How serious is the NoSQL threat? Justify your answer. What
responses by existing DBMS vendors are sensible?
• The companies that developed the NoSQL solutions were dealing
with a specific, unique processing problem – processing massive
amounts of data on thousands of servers. Existing DBMS
products were not designed to deal with this particular issue
effectively. Existing DBMS vendors should not ignore this issue,
but also should not feel that they are doomed.
• The particular processing requirements that
Google/Amazon/Facebook etc. faced are not necessarily going to
be faced by every organization. There will still be a need for a
traditional DBMS for many organizations. The DBMS vendors
will want to evaluate how best to offer this type of data store for
their customers who need it – perhaps by offering to support the
transition to the open source product for those customers who
require its capabilities.
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3. Is it a waste of your time to learn about the relational model
and Microsoft Access? Why or why not?
•
• Learning about the relational model and how to use Access
gives a student a good foundation in data management
concepts.
• As stated earlier, not every organization will require the
capabilities provided by the NoSQL data store. People using
databases for personal productivity purposes will certainly
not be moving to the NoSQL data store.
• So, learning about relational databases and Access is still a
good investment in time and effort for students today.
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4. Given what you know about GearUp, should it use a
relational DBMS, such as Oracle Database or MySQL, or
should it use Cassandra?
•
• GearUP most likely can utilize a relational DBMS effectively
and will not require a data management approach like
Cassandra. GearUp probably does not have the volume of
transactions or servers to justify a NoSQL approach.
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5. Suppose that GearUp decides to use a NoSQL solution, but a
battle emerges among the employees in the IT Department. One
faction wants to use Cassandra, but another faction wants to
use a different NoSQL data store, named MongoDB
(www.mongodb.org). Assume that you’re Kelly, and Lucas asks
for your opinion about how he should proceed. How do you
respond?
•
• Kelly should tell Lucas that the decision to use a specific
NoSQL solution should be based on a careful analytical
evaluation of GearUp’s requirements. There is no reason for
this to become a factionalized debate.
• Determine exactly what GearUp’s needs are and then
determine, analytically, how well Cassandra and mondoDB
satisfy those requirements.
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5. (cont.)
•
• Once each of the NoSQL’s capabilities have been objectively
researched and matched to the company’s real requirements,
the best fit should become apparent. Requirements should
include technical feasibility, economic feasibility, and
organizational feasibility issues in order to be complete.
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