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Harvard University *
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260
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Information Systems
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Nov 24, 2024
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Week-2
Generalization and specialization processes cannot occur smoothly without the
involvement of the inheritance mechanism, and the hierarchical position of entities does not
hinder the acquisition of traits through this phenomenon. Inherited traits become specialized and
categorized to suit software developers' requirements. For successful execution of Inheritance
concept employing Protocols is recommended. To gain certain or all attributes from another class
it is necessary to observe an established set of protocols. By utilizing both generalization and
specialization many subordinate classes can be produced from a common superior class.
According to You et al. (2022), the process of inheritance allows lower-level entities, also known
as subclasses, to acquire properties from higher-level entities, or superclasses.
Specialization is an extension of inheritance that allows for multiple derived classes from
one base class and we'll explore this notion more in the subsequent section, while inheritance
does not impose any restrictions on results unlike the strict boundaries of discipline. For creating
a hierarchy of inheritance you need to have a parent type that gives birth to one or more child
types. According to research conducted by Li et al. (2022), it was found that if a reference
category possesses a pointer then inheritance of properties into the previous classification occurs.
When two types share a member with an identical name they can establish an inheritance
relationship. However, maintaining an appropriate relationship between superclass and subclass
is crucial in utilizing inheritance mechanisms properly - even if there are multiple subclasses
within the former. A method or an attribute may be present in a supertype.
Reference
Li, X., Ma, Z., & Luo, S. (2022, July). Blockchain-Oriented Privacy Protection with Online and
Offline Verification in Cross-Chain System. In 2022 International Conference on
Blockchain Technology and Information Security (ICBCTIS) (pp. 177-181). IEEE.
You, L., Fang, M., Zhou, M., Li, H., Hao, M., Cheng, S., & Cai, M. (2022). An Ontology-Based
Knowledge Evolution Mechanism to Support the Adaptive Design of Autonomous
Transportation System. In CICTP 2022 (pp. 182-192).
Reply 1
The processes of generalization and specialization in software development rely heavily
on inheritance. Because entities can take on new characteristics, new classes can be made.
Attributes from other classes can be obtained by adhering to established procedures. For efficient
use of inheritance mechanisms and code reuse, it is essential that the relationship between
superclasses and subclasses be properly maintained.
Reply 2
Inheritance plays a critical role in facilitating software development's generalization and
specialization processes. It makes it easier to create subclasses by letting entities inherit
properties from superclasses. By adhering to protocols, classes can share attributes, allowing for
greater code reuse. Effective use of inheritance for hierarchical structures relies on keeping the
right kind of relationship between superclasses and subclasses.
Week-3
Discuss some types of queries for which renaming of attributes is necessary to specify the
query unambiguously.
Ambiguous attribute names:
Queries referencing several tables require renaming of shared
prefixed and suffixed attributes present in the rows of one particular table to prevent ambiguity
(Petersohn 2021), and when people discuss changing attribute names it’s often referred to as
attribute renaming. It is recommended that you change the 'name' attribute in both your customer
as well as your product tables for greater clarity. To make things less confusing, you may choose
customer name for one table while labelling another product name
.
Self-joins:
The usual procedure involves renaming attributes after performing a self join,
through this practice it is feasible to distinguish attributes from both tables: joined and original.
To achieve accurate search results it is important to choose the appropriate attribute
.
Discuss the various types of inner join operations.
1.
The term theta juncture refers to a specific point or moment in time. The theta join is an
extension of the join operation in database theory. This feature enables the inclusion of
supplementary joining conditions that go beyond basic equality. As a substitute, it enables
a diverse range of comparison operators such as >, <, =, and numerous others. The Theta
join operation is a useful tool for performing joins that involve non-equality conditions.
2.
The act of performing an inner join operation on a table, whereby the table is joined with
itself, is commonly referred to as a self-join. Consequently, we can assert that the table
has undergone a self-join. The capability of comparing rows within a single table on the
basis of a common attribute is advantageous. It is a customary procedure to alter the
names of attributes in the context of self-joins, in order to facilitate the differentiation
between the original and the joined tables.
Why is theta join required?
The theta join operation is deemed necessary owing to its capacity to establish join
conditions that go beyond mere equality (Bellas, 2022). For the majority of applications, joins
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that are based on equality are satisfactory. In certain instances, a more precise comparison
operator may be necessary, particularly when juxtaposing two dates, numerical ranges, or string
patterns. The theta join facilitates the direct expression of complex conditions within the join
clause.
Reference
Bellas, C. (2022).
Advanced Joins on GPUs
(Doctoral dissertation, Αριστοτέλειο Πανεπιστήμιο
Θεσσαλονίκης (ΑΠΘ). Σχολή Θετικών Επιστημών. Τμήμα Πληροφορικής. Εργαστήριο
Τεχνολογίας και Επεξεργασίας Δεδομένων).
Petersohn, D. (2021).
Dataframe Systems: Theory, Architecture, and Implementation
. University of
California, Berkeley.
Reply 1
The significance of query attribute renaming is precisely stated. This is an important step
in creating meaningful, ambiguous aliases. Inner join operations can be performed by database
administrators in a variety of ways. Equi-join, natural join, theta join (used for non-equality
conditions), cross join, and self-join are some examples. We'll look at how theta join can be used
to improve join capabilities for retrieving complex data today. Theta joins are useful in data
analysis because they allow us to compare values using operators other than equality.
Reply 2
The discourse presents a lucid and articulate exposition on the subject of inner join
operations and attribute renaming. The provided examples serve to elucidate the process of
attribute renaming and the various types of join operations. The practical application of the theta
join and its function in bridging gaps are noteworthy.
Week-4
What is ODBC? How is it related to SQL/CLI?
ODBC protocol boasts extensive support in terms of API coverage, achieving this goal
demands conducting a thorough database search operation that entails examining many records
(Khan et al., 2023). Interfacing with and utilizing the SQL database language can be
accomplished using an application programming interface known as SQL/CLI at a call level,
through which the user interface language can be manifested. The responsibility for shaping the
system into its present form falls squarely on ODBC since they were originally responsible for
developing it, and the system is reliant on ODBC in order for it to exist.
What are the three main approaches to database programming
?
1.
Embedded SQL:
Embedded SQL is comparable to some extent with the performance of
both C and C++ applications while providing valuable benefits such as optimized code
including efficient data access algorithms perfect for fast-paced application development.
Additionally, the size of your database can be decreased by utilizing embedded SQL
instead of employing an UltraLite component in cases where just a few tables are
involved.The use of a tailored compiled edition of the UltraLite database engine in each
application's SQL integration causes this, but when several tables come into play, the
benefit no longer exists. C or C++ programming knowledge is a prerequisite to using the
interface. Without prior experience with either of these two programming languages, it's
better to go for a different option in the UltraLite interface. Developers can choose from a
variety of interface options available in the UltraLite components that cater to different
programming languages and development tools.
2.
OBDC/SQL CLI:
With its wide implementation among different databases, the ODBC
and SQL CLI offer developers uniformity in terms of their capabilities with respect to
data types. Getting used to the interface and discovering pertinent support resources
becomes effortless while using this tool.In contrast to alternatives such as embedded
SQLs, the use of ODBC and SQL CLI interfaces may pose disadvantages stemming from
their increased complexity. Software developers may find it necessary to spend additional
time getting acquainted with the interface before developing code that works on multiple
database management systems.
3.
Object Relational Mapping:
The primary advantage of object-relational mapping (ORM)
is that it allows developers to communicate with databases regardless of the underlying
database management system. This has the potential to make it easier to switch between
databases or use multiple databases in a single application. When dealing with complex
or antiquated databases, ORM solutions can be a pain to set up and configure. This is a
major drawback, especially when dealing with legacy databases.
Reference
Khan, W., Kumar, T., Zhang, C., Raj, K., Roy, A. M., & Luo, B. (2023). SQL and NoSQL Database
Software Architecture Performance Analysis and Assessments—A Systematic Literature
Review.
Big Data and Cognitive Computing
,
7
(2), 97.
Reply 1
The discourse is thorough and captivating, prompting me to delve deeper into the drawbacks
associated with ORM. One of the most compelling drawbacks pertains to the execution of
multiple queries against an Object-Relational Mapping (ORM) system in order to retrieve all the
requisite data. This is the reason why individuals hold the belief that Object-Relational Mapping
(ORMs) are comparatively slower than utilizing plain SQL.
Reply
2
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Given the aforementioned points, I wholeheartedly agree. Through my investigation, I have
discovered a prospective advantage associated with the implementation of the Embedded SQL
approach, which I would like to impart to you. Embedded SQL has the potential to enhance
processing speed as the database engine directly executes the SQL commands. Embedded SQL
has the potential to provide satisfactory efficiency in certain cases.
Week-5
What is the difference between primary and secondary storage?
Data storage refers to the process of preserving and retaining information and data within
a computer's storage medium. Computers employ diverse techniques for data storage, resulting
in distinct tiers of data storage that encompass primary and secondary storage. The primary data
storage, commonly known as primary memory, serves as the principal storage hub of a computer
system. The primary memory is a temporary storage location that primarily contains data and
information that are currently being utilized by the computer. The primary data category
encompasses three distinct types of memory: random access memory (RAM), read-only memory
(ROM), and a more advanced iteration of ROM referred to as programmable read-only memory
(PROM). Secondary data storage serves as an alternative storage facility that enables the
permanent retention of data and information. In contrast to primary data that exhibits volatility,
secondary storage is characterized by non-volatility and is not directly accessible by the central
processing unit. The category of secondary storage encompasses various types of storage
devices, including hard disk drives (HDDs), optical media devices like CDs and DVDs, USB
flash drives, and floppy disks.
Discuss the mechanism used to read data from or write data to the disk
The access arm of a disk is what reads and writes information to and from the disk. This
arm moves a read/write head to a certain track on a disk. A read/write head floats just above the
track at the end of the access arm, it does not touch the surface of the disk.
What is the difference between static and dynamic files?
Static files remain unchanged during the runtime of an application or when it is being executed
on a computer. In addition, it has been suggested by Ijaz et al. (2019) that static files are essential
for enhancing computer applications. Conversely, dynamic files possess the capability to modify
and manipulate the resulting output based on the data that is entered into the file.
Reference
Ijaz, M., Durad, M. H., & Ismail, M. (2019, January). Static and dynamic malware analysis using machine
learning. In
2019 16th International bhurban conference on applied sciences and technology
(IBCAST)
(pp. 687-691). IEEE.
Reply 1
The arguments articulated in your discourse exhibit logical consistency with the concepts
that I encountered in my scholarly investigation and literary analysis. Primary and secondary
storage exhibit several distinctions, including their respective speeds, with primary storage being
superior in terms of velocity. Furthermore, it is worth noting that secondary storage data is not
subject to loss in the same manner as primary storage, which is susceptible to data loss in the
event of a power outage.
Reply 2
The arguments expounded in your discourse are cogent and I concur with the
methodology you presented in addressing the inquiries. The elucidation of the distinction
between dynamic and static files is presented in a straightforward and comprehensible manner.
The discourse has facilitated my enhanced comprehension of the concept. One notable
distinction between primary and secondary storage pertains to their respective storage capacities,
with primary storage typically exhibiting lower storage capacity relative to secondary storage.
Week-6
Discuss the different types of parameters that are used in cost functions. Where is this
information kept?
Each optimization of a database query involves the utilization of cost function
characteristics that are stored within the database management system (DBMS). According to
Lan et al. (2021), the primary function of cost function components is to provide information for
query optimization in information applications. In order to enhance productivity, it is imperative
to optimize various parameters to expedite the execution of queries and improve their
functionality. The crucial factors that require consideration encompass the size parameters
pertaining to multiple files exhibiting identical data types. The parameters include:
1.
Number of file blocks
2.
Number of records
3.
The average size of records
The aforementioned requirements play a crucial role in the event of executing various
algorithms. Furthermore, mathematical equations are employed to designate cost functions,
which are intended for the optimization of queries. Moreover, the parameter of the number of
distinct values must be taken into consideration.
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Discuss the cost components for a function used to estimate query execution cost. Which cost
components are used most often as the basis for cost functions?
The constituents of a function utilized for approximating query execution expenses
comprise the cost of accessing secondary storage, which pertains to the cost incurred in the
process of reading and writing data blocks (Wan et al., 2021). The cost of disk storage is a
component of the function and pertains to the expenses incurred in storing intermediate files
generated during query execution. In addition, the cost function for query execution includes
computation and communication expenses. The commonly utilized cost elements comprise
expenses related to accessing secondary storage, costs associated with disk storage, and costs
incurred for computation.
Reference
Lan, H., Bao, Z., & Peng, Y. (2021). A survey on advancing the dbms query optimizer:
Cardinality estimation, cost model, and plan enumeration.
Data Science and
Engineering
,
6
, 86-101.
Wan, L., Huebl, A., Gu, J., Poeschel, F., Gainaru, A., Wang, R., ... & Klasky, S. (2021).
Improving I/O performance for exascale applications through online data layout
reorganization.
IEEE Transactions on Parallel and Distributed Systems
,
33
(4), 878-890
Reply 1
I concur with the cogent explication of the salient points in the discourse, as I have
acquired a plethora of discernments from the lucid elucidation proffered. Furthermore, it is
pertinent to acknowledge that network and concurrency costs are crucial variables that warrant
consideration. However, it is important to note that their significance may vary across different
database environments, as they may assume a secondary role in some cases.
Reply 2
The salient points articulated in the discourse are congruent with my preexisting notions,
with certain aspects of the discourse resonating with the points I had previously jotted down. The
author notes a distinct cost factor, namely the network cost, which pertains to the expenses
incurred in transmitting data within a given network. The cost of a network is determined by the
volume of data being transmitted and the bandwidth capacity of the network during the
transmission process.
Week-7
Discuss the UNDO and REDO techniques of recovery. What are the advantages and
disadvantages of this technique?
Databases possess a characteristic termed as Undo/Redo that enables users to retrieve any
failed transaction (Kuhn et al., 2022). If there happens to be any error with regards to
malfunctioning of the system or if it encounters some issue during carrying out transactions then
alterations made along with their respective value will securely get logged into a particular
memory location which is accessible solely to the algorithm.The backed up unsuccessful result
can be retrieved by utilizing a saved value. To return modified data values to their initial state
after a transaction has been executed use the UNDO command. If required it is possible to roll
back changes made to modified data using the UNDO option. The Undo and Redo functionalities
enable the user to reverse or repeat one or more keystrokes, albeit solely in the precise sequence
in which they were executed, precluding the possibility of skipping any steps. In the event of a
system failure, any modifications that have not yet been implemented in the database may be lost
if the log is not adequately maintained or if it becomes corrupted.
Discuss how disaster recovery from catastrophic failures is handled.
The primary approach for addressing catastrophic failures such as disk crashes is through
the implementation of database backup (Tyagi et al., 2019). Periodic backups of the database and
log are conducted onto cost-effective storage media, such as magnetic tapes. In the case of a
complete system malfunction, the restoration of the system can be achieved by transferring the
latest backup version from tape storage to disk. The customary practice is to periodically archive
the system log onto magnetic tape as a precautionary measure against potential loss of data that
may have ensued subsequent to the previous backup due to transactions. The comparatively
reduced size of the system log in comparison to the database renders it amenable to more
frequent backup. In the event of a system log backup, there is no loss of user data that has been
modified or added subsequent to the previous database backup.
Reference
Kuhn, D., Kyte, T., Kuhn, D., & Kyte, T. (2022). Redo and Undo.
Expert Oracle Database Architecture:
Techniques and Solutions for High Performance and Productivity
, 429-501.
Tyagi, V., Arora, R., Ram, M., & Yadav, O. P. (2019). 2-Out-of-3: F System analysis under catastrophic
failure.
Nonlinear Studies
,
26
(3).
Reply 1
Consistent backups and system log archiving are critical for database disaster recovery.
The risk of data loss can be reduced to an acceptable level if backups are stored on reliable media
and a detailed log is kept and updated on a regular basis. These procedures not only protect data
integrity in the event of a catastrophic failure, but they also lay the groundwork for rapid data
restoration. To protect critical information and ensure the smooth operation of businesses, strong
backup strategies must be implemented.
Reply 2
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Disaster recovery protocols, which are implemented in databases through regular
backups, serve as a safeguard against catastrophic system malfunctions. The mitigation of data
loss can be achieved through the implementation of measures such as the preservation of
duplicates of vital information in secure locations and the perpetual retention of system logs.
This approach offers protection against system failures by ensuring data integrity and facilitating
restoration, thereby serving as a form of insurance.
Week-8
Database Authorization
The process of authorizing access to a database is of utmost importance and is carried out
by the database manager. This involves the retrieval of information pertaining to a user who has
been authenticated. The data acquired by the manager is utilized to ascertain the database
operations that are accessible to the user and the database entities that the user can employ.
Access Control
Access control is a fundamental aspect of both physical and internet security, designed to
prevent unauthorized access and utilization of database information (Mazhar et al., 2023). Access
control is a mechanism that enables an organization to determine and regulate authorized access
to its corporate resources and data in a selective manner. Access control is a mechanism that
employs policies to authenticate users who are authorized to gain access, thereby ensuring
compliance with established regulations.
Data Encryption
Data encryption is a security measure that involves the conversion of plain text, also
referred to as unencrypted data, into a complex form of data called ciphertext or encrypted data.
Secure data transmission is ensured by the requirement of a specific key for decryption by the
user.
Privilege Account
Privileged (system) account are considered administration accounts which are login
credentials to specific serveres, the administrative accounts and firewalls.
Database Audits
Database audits is the process through which the database use is monitored and the
actions of the users followed up for security purposes.
Audit Trail
Audit trail is the procedural recordings of the computer events regarding the undertaken
operating system, the activities conducted by the user and the application
((
Mazhar et al., 2023)).
Privilege and Types
Privileges refer to commands that involve the granting and revocation of commands for
individual accounts, users, or groups of users. The various types of permissions include
automatic permissions that do not require explicit authorization, granted privileges that are
obtained by presenting appropriate credentials, and applied permissions that are executed
through a program.
Administrative
User privilege
Application privilege
Root privilege
What is meant by revoking a privilege?
Commands are granted temporarily, the cancelation of the privilege after completing the
task is done through a revoke command. The process of cancelation is called a revoking
privilege.
Reference
Mazhar, T., Irfan, H. M., Khan, S., Haq, I., Ullah, I., Iqbal, M., & Hamam, H. (2023). Analysis of Cyber
Security Attacks and Its Solutions for the Smart Grid Using Machine Learning and Blockchain
Methods.
Future Internet
,
15
(2), 83.
Reply 1
I agree with the points presented in the discussion, most of which are coherent with the
points I presented in my discussion. However, I had additional different types of privilege in my
discussion the network privilege where user has access to the drives and servers. Also, the file
system privilege where the user has access to files and directories.
Reply 2
The discussion has well-articulated points, presenting ideas in an insightful and easier
language. I have learnt a new concept that I initially did not cover through my reading and
research. The root privilege, a concept I just heard in passing but did not look into it deeply.
However, through your discussion I have researched the concept.
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