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1-2-3 Conceptual Design of Databases

Conceptual design of databases is the process of creating conceptual data models. For that, it is necessary to conduct data analysis at the beginning. The data analysis identifies the data that is required for the targeted operations where database is implemented, and then the meaning and relation of this data are analyzed and summarized. In addition, data items are standardized by using rules such as naming convention in order to eliminate data duplication. Metadata such as names, meanings, or attributes of data items are recorded in the data dictionary for users in DD/D (Data Dictionary/Directory) to ensure that synonyms/homonyms do not occur. The conceptual data model is created on the basis of the results of data analysis. For the conceptual data model, it is common to use E-R model (i.e., E-R diagram) that represents the target content with two concepts of entity and relationship. · 2 questions

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In E-R model, it is possible to represent cardinality (i.e., multiplicity) of the relationship. There are three types of cardinality: “one-to-one”, “one-to-many”, and “many-to-many”. For example, Figure 4-4 in the E-R model shows a “many-to-many” relation where one instructor delivers a lecture to multiple students, and one student attends lectures of many instructors.

When cardinality in E-R model is represented, “Many” is also represented as “*”, “M”, or “N”. Another notation method is to directly connect two entities with a line as shown in Figure 4-5. In this case, an arrow on the line means “Many.” Figure 4-5 shows that multiple types of products are purchased from a wholesaler, and products are always purchased from the same wholesaler. · 3 questions