Course: Database Systems 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
Substantive replies for the below posts:
Post 1:
Ramya
Discussion-1
COLLAPSE
Top of Form
DISCUSSION 1
The ER model is used to represent real life scenarios as an entity. The properties of these entities are characterized in the ER diagram and their links are represented as relationships. The ER model is extended here, we use two new modeling constructs, one is the substrate, the other is the supertype. A subset of entities in an entity type. The supertype is a type of entity. The BOTTOM-UP process is the process of defining a more general entity type from a set of more specialized entity types. it is the process of identifying high level entities for lower level entities. Create a supertype from a series of subtypes. The TOP-DOWN approach is the process of defining one or more subtypes of supertype it. It is the process of identifying lower level entities from a higher level entity. Create subtypes from a transcript. A characteristic of the supertype whose values determine the subtypes. A simple attribute with alternate values to express the possible subtypes. A composite entity whose sub-parts are associated with various sub-types. The E-R model can be easily converted to a relational database. There is no data manipulation language available for the E-R model as it is largely an abstract concept. The object-oriented data model is based on the use of real scenarios. In this model, scenarios are represented as objects. Objects with similar functionality are grouped together and linked to various other objects. The object-oriented model is quite flexible in most cases. This model can be quite complex to create and understand.
Reference:
Beyond the First Entity Diagram. (2011). Database Design Using Entity-Relationship Diagrams, 129-150. doi:10.1201/9781439861776-9
Chapter 4 The Enhanced Entity-Relationship (EER) Model. (2017, August 26). Ppt Video Online Download. https://slideplayer.com/slide/5916006
Bottom of Form
Post 2:
16 hours ago
Tera
Tera Discussion 1 Week 5
COLLAPSE
Top of Form
Tera K. Brown
ITS538 – Database Systems
Week 5 Discussion 1
March 31, 2021
In comparing inheritance in the EER model to inheritance in the OO model, we need to understand the goal of each model. EER database is close to real world situations, data, and scenarios, conversely OO model is more based on concepts that are abstract or do not exist.
In the EER model there are subclasses, superclasses, and inheritances. The inheritance aspect if the EER model is how the relationships between the subclasses and the type of entities in which they relate. (Elmasri, Navathe, 2017) Simply stated, any entity that is a member of a subclass will inherit all the relationships that the superclass participates in. The EER model is more of a high-level concept design approach allowing for more precise and complex classes to be associated through attributes and relationships.
In the OO model, both attributes and operations can be inherited. This model and its inheritance allow a new type to be defined based on certain other predefined types which then leads to a type hierarchy. (Elmasri, Navathe, 2017) The assignment of a type transpires by assigning a name, attributes, and operations. These attributes and operations combined are referred to as functions. Object Oriented inheritance allows many different sets and extents of membership. The concept of object-oriented models is basing an object or class on another object or class while retaining similarities.
References
Elmasri, R., & Navathe, S. B. (2017). Fundamentals of Database Systems (7th ed.). Pearson.
Bottom of Form
