Compare Inheritance in the EER model to Inheritance in the OO Model
Create a discussion thread (with your name) and answer the following question(s):
Discussion 1 (Chapter 12): Compare inheritance in the EER model (see Chapter 4) to inheritance in the OO model described in Section 12.1.5
Instructions: Your response to the initial question should be 250-300 words. Next respond to two postings provided by your classmates. The first post should be made by Wednesday 11:59 p.m., EST. I am looking for active engagement in the discussion. Please engage early and often. You are require to create your initial thread in order to view and respond to the threads posted by other students. There must be at least one APA formatted reference (and APA in-text citation) to support the thoughts in the post as needed. Do not use direct quotes, rather rephrase the author’s words and continue to use in-text citations.
Week 5: Discussion 2
Week 5: Discussion 2 Create a discussion thread (with your name) and answer the following question(s):
Discussion 1 (Chapter 13): What are the differences between structured, semi structured, and unstructured data?
Instructions: Your response to the initial question should be 250-300 words. Next respond to two postings provided by your classmates. The first post should be made by Wednesday 11:59 p.m., EST. I am looking for active engagement in the discussion. Please engage early and often. You are require to create your initial thread in order to view and respond to the threads posted by other students. There must be at least one APA formatted reference (and APA in-text citation) to support the thoughts in the post as needed. Do not use direct quotes, rather rephrase the author’s words and continue to use in-text citations.
Sample Paper
Week 5: Discussion 1 Create a discussion thread (with your name) and answer the following question(s):
Discussion 1 (Chapter 12): Compare Inheritance in the EER model to Inheritance in the OO Model
In EER modeling, an entity type represents both a type of entity and the collection of entities of that type existing in the database. In several cases, an entity type comprises many subtypes of its entities that need explicit representation as they are essential to the database application. This relationship is typically called a supertype/subtype or a superclass/subclass relationship (Elmasri & Navathe, 2016). An entity in a database exists as a member of both the subclass and the superclass. Type inheritance is one important concept linked to subtypes/subclasses. Since an entity in a subclass characterizes the same entity in a superclass, it should possess values for its attributes and its attributes as the superclass member. In this case, the subclass member entity inherits all the characteristics of the superclass member entity. The entity also inherits every participating relationship of the superclass (Elmasri & Navathe, 2016). A subclass, with its attributes and relationships collectively with all inherited attributes and relationships from the superclass, can be termed an entity type.
Inheritance and class hierarchies are also key concepts in OO modeling, which permit new specification classes or types to inherit most of their structures from classes or types that were previously defined. With this, data types can be incrementally developed, and existing type definitions can be reused when new types of objects are being created. In a nutshell, inheritance permits the definition of new types based on already defined types, resulting in a hierarchy. To define a type, assign a name to it and define several operations and attributes for the type. An example is a type describing the characteristics of a PERSON as seen below (Elmasri & Navathe, 2016):
PERSON: Name, Address, Birth_date, Age, Ssn
The notion of subtype is important when creating a new type that is similar but unidentical to a type that has already been defined (supertype). An example is the representation of STUDENT and EMPLOYEE relative to PERSON as follows (Elmasri & Navathe, 2016):
EMPLOYEE: Name, Address, Birth_date, Age, Ssn, Salary, Hire_date, Seniority
STUDENT: Name, Address, Birth_date, Age, Ssn, Major, Gpa
EMPLOYEE and STUDENT have their functions and those defined in PERSON, and so they are
both subtypes of PERSON.
Reference
Elmasri, R., & Navathe, S.B. (2016). Fundamentals of Database Systems. Pearson Company
Instructions: Your response to the initial question should be 250-300 words. Next respond to
two postings provided by your classmates. The first post should be made by Wednesday 11:59
p.m., EST. I am looking for active engagement in the discussion. Please engage early and often.
You must create your initial thread to view and respond to the threads posted by other students.
There must be at least one APA formatted reference (and APA in-text citation) to support the
thoughts in the post as needed. Do not use direct quotes, rather rephrase the author’s words, and
continue to use in-text citations.
A subclass with more than one superclass in the EER model is called a shared subclass leading to
multiple inheritance. The existence of at least one shared subclass results in a lattice and hence
multiple inheritance. When no shared subclasses exist, the result becomes a hierarchy instead of
a lattice, and thus, a single inheritance would exist.
One concept in OO modeling is selective inheritance which happens when a subtype inherits
only some of the functions of a supertype. An EXCEPT clause may be used in this case to list the
supertype functions that the subtype need not inherit. This mechanism is not habitually provided
in OO models but is more commonly used in artificial intelligence applications.
