Assignment Task:
Discussion Instructions: Relationships and Inheritance and EER Models
250 words total, answer the questions below with 4 evidence base scholarly articles. APA format.
1. Describe the mechanism of attribute/relationship inheritance. Why is it useful?
2. Discuss the options for mapping EER model constructs to relations.
400 words total, replying to the two posts below. Each reply must be 200 words for post 1 and post 2.
T.TPost #1
Hell Class,
According to Elmasri and Navathe (2016), the EER model is a high-level conceptual model used to describe the relationships between objects and the structure of a database. The concepts of Generalization and Specialization were introduced to minimize the complexity that emerges when designing database models. Generalization is extracting standard features from different entities to create a single generalized entity called a "Superclass." In contrast, Specialization divides an entity into sub-entities based on its eminent characteristics, also known as "Subclass." It's safe to say that Generalization and Specialization are the reverse functions of each other, consequently depicting that a subclass is also an instance of a superclass. As for class/subclass relationships, a subclass entity is also a superclass member, but a superclass entity is not necessarily a subclass member. Inheritance allows the creation of a new type (attributes and operations of a SQL object) based on other pre-defined types, leading to a new type/class hierarchy. Attribute Inheritance allows subclass entities to inherit all the attributes of an entity that is a superclass member. At the same time, Participation Inheritance permits subclass entities to also inherit relationships in which superclass entities participate. Attribute and relationship inheritance could help with the efficiency of database design by establishing a hierarchical structure among tables, enabling code-reusability, simplified maintenance, and better organization of complex data structures.
Mapping EER model constructs to relations involves converting the components of the EER model, such as entities, attributes, and relationships, into a relational database format. In addition to the ER-to-relational mapping algorithm, some options include mapping Specialization into single or multiple tables, mapping categories using a Surrogate Key, and mapping multiple inheritance using the same key attribute for all shared subclasses.
Reference:
Elmasri, R., & Navathe, S. B. (2016). Fundamentals of database systems, 7th ed. New York, NY: Pearson Addison-Wesley.
ER Model, ER Diagram, and Relational Schema: What's the Difference.
J.BPost #2:
Hello Class,
According to ScienceDirect's academic journal article, "Inheritance Relationship," an inheritance relationship refers to the tiered organization of classes in object-oriented languages, also known as code around objects. Essentially, it allows different classes to be reused. For instance, inheritance enables subclasses to adapt or change the properties and behavior inherited from their superclass. This includes implementing, redefining, and adding new attributes and operations. While also, modifying access rights of those new attributes. Inheritance relationships are another source of structural information that identifies relationships between classes, and distinguishing anti-patterns that may be involved amongst the different classes (Fuentes-Hernández & Zhuge, 2005). According to our reading, the inheritance mechanism is so useful because when it identifies anti-patterns it reduces code redundancy, increases manageability, and creates an environment for versatile behavior (Elmasri & Navathe, 2015).
According to our reading, the mapping from EER models to relations involves modifying entities into tables, attributes into columns, and relationships into separate tables or foreign keys. Methods used to map these models are the single-table method, class-table method, and the concrete-table method. The single-table method, merge all entities in the hierarchy into one table. Creating columns for every possible attribute, including a differentiator column to specify the entity type. The class-table method, separates the superclass from its subclass. Which allows better management over specific attributes. The concrete-table method, are results from each subclass that includes all attributes from its superclass. This method duolicates shared information, which is helpful for queries that call for that specific function (Elmasri & Navathe, 2015).
References:
Elmasri, R., & Navathe, S. B. (2015). Fundamentals of Database Systems (7th ed.). Pearson Education (US).
Zhuge, Hai, and Rubén Fuentes-Hernández. (2005). "Inheritance Relationship." Inheritance Relationship - an Overview | ScienceDirect Topics