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English Sentence Structure and Entity-Relationship Diagrams

English Sentence Structure and Entity-Relationship Diagrams. Relationship to Course: -Textbook Chapters 7 -10 on Conceptual Data Model - Lab 2 Part III - Building conceptual data model from document

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English Sentence Structure and Entity-Relationship Diagrams

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  1. English Sentence Structure and Entity-Relationship Diagrams • Relationship to Course: • -Textbook Chapters 7 -10 on Conceptual Data Model • - Lab 2 Part III - Building conceptual data model from document • Reference: Peter P. Chen, “Entity-Relationship Diagrams and English Sentence Structure”, Proceedings of the 1st International Conference on the Entity-Relationship Approach to Systems Analysis and Design, p.13-14, January 1980, http://dl.acm.org/citation.cfm?id=726196 Jian Liu and Bo Xue Csci 5707: Introduction to Databases, Fall 2013

  2. Motivation • Entity Relationship Diagram (ERD) Promise: • easy to understand • ERD Challenge: • Old Approach: DB designer study old system documents • Difficult to translate requirements documents into DB schemas • Proposed Approach: • 11 translation rules • More like hints and guidelines than strict rules!

  3. First 4 Rules • 1: common noun => an entity type • 2: transitive verb => a relationship type • 3: adjective => an attribute of an entity • 4: adverb => an attribute of a relationship • Example: • A 40-year-oldpersonworks on a project with project number 2175 for20% of his time. • ERD

  4. Next 4 Rules • 5: Convert “There are … X in Y,” into the equivalent form “Y has … X” • Leading Question for Rules 6 and 7: Convert following to ERD (6): The father of James Smith is Robert Smith (7): The color of the desk is blue • 6,7: “The X of Y is Z” • 6. if Z is a proper noun, we may treat X as a relationship between Y and Z • 7. if Z is NOT a proper noun, we may treat X as an attribute of Y • and Z represents a value of X. • 8: objects of algebraic or numeric operations => attributes • Note: can be derived from Rule 7. • Ex: “The average salary is $20,000.” = “The average salary of employee is $20,000.”

  5. Rule 9 • 9: A gerund => a relationship-converted entity type • Example: “Products are shipped to customers, and the shipping is performed by clerks” • Note: Chen’s notation is different from Textbook notation. Ship CUSTOMER PRODUCT CLERK

  6. Rules 10, 11 • 10: A clause in English is a high-level entity type abstracted from a group of interconnected low-level entity and relationship types in ERD • 11: A sentence in English corresponds to one or more entity types connected by a relationship type, in which each entity type can be decomposed into low-level entity types interconnected by relationship types • Example: “The manager decides which machine is assigned to which employee” • Leading Question? Is this model allowed by Textbook ? Hint: It has a relationship involving another relationship!

  7. Exercise Develop ERD in Textbook notation for “The manager decides which machine is assigned to which employee” Do not show cardinality & participation constraints. Do not show sub-type super-type. Compare possible model for • Ability to detail employee, machine, … • ERD to Table conversion rules • Redundancy MANAGER ASSIGNMENT MANAGER Assign MACHINE EMPLOYEE for ASSIGNMENT EMPLOYEE MANAGER MANAGER MACHINE MANAGER Assign Assign EMPLOYEE EMPLOYEE MACHINE MACHINE for ASSIGNMENT EMPLOYEE Decide Decide Decide to MACHINE

  8. Questions?

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