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Questions and Answers
What is the main purpose of a Data Model?
What is the main purpose of a Data Model?
Which category of data models consists of fixed format records with each field typically of a fixed length?
Which category of data models consists of fixed format records with each field typically of a fixed length?
What does a hierarchical data model consist of?
What does a hierarchical data model consist of?
Which type of language is considered too low-level to describe an organization's data requirements effectively?
Which type of language is considered too low-level to describe an organization's data requirements effectively?
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What does a data model help to understand?
What does a data model help to understand?
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In the context of data models, what does 'Record-based' refer to?
In the context of data models, what does 'Record-based' refer to?
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Explain the main purpose of a data model in the context of databases.
Explain the main purpose of a data model in the context of databases.
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Describe the distinguishing characteristics of record-based data models.
Describe the distinguishing characteristics of record-based data models.
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Why is a higher-level data model language necessary for describing an organization's data requirements?
Why is a higher-level data model language necessary for describing an organization's data requirements?
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How does a data model assist in understanding the relationship between entities in a database?
How does a data model assist in understanding the relationship between entities in a database?
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Explain the significance of object-based data models in the classification of data models.
Explain the significance of object-based data models in the classification of data models.
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What are the main advantages of the Hierarchical Data Model?
What are the main advantages of the Hierarchical Data Model?
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What is a key disadvantage of the Hierarchical Data Model in terms of processing nature?
What is a key disadvantage of the Hierarchical Data Model in terms of processing nature?
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How does the Network Data Model differ from the Hierarchical Data Model in terms of relationships between entities?
How does the Network Data Model differ from the Hierarchical Data Model in terms of relationships between entities?
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What is a major advantage of the Network Data Model in handling relationships?
What is a major advantage of the Network Data Model in handling relationships?
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Who developed the Relational Data Model and in which year?
Who developed the Relational Data Model and in which year?
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Study Notes
Data Model
- A set of concepts to describe the structure of a database and certain constraints that the database should obey.
- A description of the way that data is stored in a database.
- Helps to understand the relationship between entities and to create the most effective structure to hold data.
- A collection of tools or concepts for describing data, data relationships, data semantics, and data constraints.
Categories of Data Models
- Object-based
- Record-based
- Physical-based
Record-based Data Models
- Consist of a number of fixed format records.
- Each record type defines a fixed number of fields; each field is typically of a fixed length.
Hierarchical Data Model
- The simplest data model.
- Record type is referred to as node or segment.
- Nodes are arranged in a hierarchical structure as a sort of upside-down tree.
- A parent node can have more than one child node.
- A child node can only have one parent node.
- The relationship between parent and child is one-to-many.
- Relation is established by creating physical link between stored records.
Advantages of Hierarchical Data Model
- Simple to construct and operate on.
- Corresponds to a number of natural hierarchically organized domains.
Disadvantages of Hierarchical Data Model
- Navigational and procedural nature of processing.
- Database is visualized as a linear arrangement of records.
- Little scope for "query optimization".
Network Data Model
- Allows record types to have more than one parent unlike hierarchical model.
- A network data model sees records as set members.
- Each set has an owner and one or more members.
- Allow many to many relationship between entities.
Advantages of Network Data Model
- Able to model complex relationships and represents semantics of add/delete on the relationships.
- Can handle most situations for modeling using record types and relationship types.
- Language is navigational; uses constructs like FIND, FIND member, FIND owner, FIND NEXT within set, GET etc.
Disadvantages of Network Data Model
- Navigational and procedural nature of processing.
- Database contains a complex array of pointers that thread through a set of records.
- Little scope for automated "query optimization”.
Relational Data Model
- Developed by Dr.Edgar Frank Codd in 1970.
- Terminologies originate from the branch of mathematics called set theory and relation.
- Can define more flexible and complex relationship.
- Viewed as a collection of tables called “Relations” equivalent to collection of record types.
- Relation: Two dimensional table that stores information or data in the form of tables.
- A row of the table is called tuple (equivalent to record).
- A column of a table is called attribute (equivalent to field).
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Description
Explore the concepts related to data models, including the structure of a database, constraints, and the need for a higher-level language. Learn how data models help in describing data requirements for organizations in a more understandable manner.
