Presentation on theme: "Chapter 3 The Enhanced E-R Model"— Presentation transcript:
1 Chapter 3 The Enhanced E-R Model Jason C. H. Chen, Ph.D.Professor of MISSchool of Business AdministrationGonzaga UniversitySpokane, WA 99258
2 Objectives Define terms Understand use of supertype/subtype relationshipsUnderstand use of specialization and generalization techniquesSpecify completeness and disjointness constraintsDevelop supertype/subtype hierarchies for realistic business situationsDevelop entity clustersExplain universal (packaged) data modelDescribe special features of data modeling project using packaged data model
3 What is the Enhanced E-R Model (EE-R Model) and Why? The Enhanced E-R model (EE-R) is an extended E-R model with new modeling constructs.Why the EE-R model?The business environment has changed dramatically.Business relationships and data are more complex.
4 Business RulesThe EE-RD are used to capture important business rules such as constraints in supertype/sbubtype relationship.The rules automatically become constraints that are forced by the DBMS and are used to maintain the organizational database in a consistent and valid state.
5 PARADIGMS (Definition) A paradigm is a way of viewing things and thinking about things.L
6 Supertypes and Subtypes Subtype: A subgrouping of the entities in an entity type which has attributes that are distinct from those in other subgroupingsSupertype: An generic entity type that has a relationship with one or more subtypes (Fig. 3-1, 2)Inheritance:Subtype entities inherit values of all attributes of the supertypeAn instance of a subtype is also an instance of the supertype
7 Figure 3-1 Basic notation for supertype/subtype notation a) EER notation
8 Figure 3-1 Basic notation for supertype/subtype notation (cont.) b) Microsoft Visio Notationb) Microsoft Visio NotationDifferent modeling tools may have different notation for the same modeling constructs
9 is_a Fig. 3-2: Employee supertype with three subtypes Generalization All employee subtypes will have employee number, name, address, and date-hiredis_aGeneralizationSpecializationhas_aEach employee subtype will also have its own attributes
12 UML notation: An example of Object-Oriented (O-O) Approach
13 Relationships and Subtypes Relationships at the supertype level indicate that all subtypes will participate in the relationshipThe instances of a subtype may participate in a relationship unique to that subtype. In this situation, the relationship is shown at the subtype level (Fig. 3-3)Subtype entities inherit values of all attributes of the supertype.An occurrence of a subtype is also an occurrence of the supertype
14 Figure 3-3 - Supertype/subtype relationships in a hospital Both outpatients and resident patients are cared for by a responsible physicianOnly resident patients are assigned to a bed
15 Generalization and Specialization Generalization: The process of defining a more general entity type from a set of more specialized entity types. BOTTOM-UP (Fig. 3-4)Specialization: The process of defining one or more subtypes of the supertype, and forming supertype/subtype relationships. TOP-DOWN (Fig. 3-5)
16 Figure 3-4 Example of generalization a) Three entity types: CAR, TRUCK, and MOTORCYCLEAll these types of vehicles have common attributes
17 Figure 3-4 Example of generalization (cont.) b) Generalization to VEHICLE supertypeSo we put the shared attributes in a supertypeMOTORCYCLEWAGONNote: no subtype for motorcycle, since it has no unique attributes
18 Figure 3-5 Example of specialization a) Entity type PARTOnly applies to manufactured partsApplies only to purchased parts
19 Figure 3-5 Example of specialization (cont.) b) Specialization to MANUFACTURED PART and PURCHASED PARTNote: multivalued attribute was replaced by an associative entity relationship to another entityCreated 2 subtypesThe same (purchased) part may be purchased from MORE THAN ONE supplierA supplier can SUPPLY more than ONE purchased part.
20 Constraints in Supertype/ Subtype Relationships Completeness Constraints: Whether an instance of a supertype must also be a member of at least one subtype.Total Specialization Rule: Yes (Fig. 3-6a - double line convention)Partial Specialization Rule: No (Fig. 3-6b - single line convention)
21 Figure 3-6 Examples of completeness constraints a) Total specialization rule
22 Figure 3-6 Examples of completeness constraints (cont.) b) Partial specialization rule
23 Constraints in Supertype/ Disjointness constraint Disjointness Constraints: Whether an instance of a supertype may simultaneously be a member of two (or more) subtypes.Disjoint Rule: An instance of the supertype can be only ONE of the subtypesOverlap Rule: An instance of the supertype could be more than one of the subtypes
24 Figure 3-7 Examples of disjointness constraints a) Disjoint rule
25 Figure 3-7 Examples of disjointness constraints (cont.) b) Overlap ruleA part may be both a Purchased Part and a Manufactured Part at the same time, but must be one or the other due to Total Specialization
26 Figure 3-7 Examples of disjointness constraints (cont.) b) Overlap rule
27 Constraints in Supertype/ Subtype Discriminators Subtype Discriminator: An attribute of the supertype whose values determine the target subtype(s)Disjoint – a simple attribute with alternative values to indicate the possible subtypes (Fig. 3-8)Overlapping – a composite attribute whose subparts pertain to different subtypes. Each subpart contains a boolean value to indicate whether or not the instance belongs to the associated subtype (Fig. 3-9)Summary Example (Fig. 3-10)
29 Figure 3-9 Subtype discriminator (overlap rule) A composite attribute with sub-attributes indicating “yes” or “no” or both (“yes” and “no”) to determine whether it is of each subtype
30 ? Figure 3-10 Example of supertype/subtype hierarchy Common attributes forall levels?Inherit all attributes from all supertypes
31 Break ! (Ch. 3 - Part I) In class exercise: #12, 13 (p. 143-144) HW turn in a hardcopy using “Visio”/WordRevise your MVC ER/M
32 Entity ClustersEER diagrams are difficult to read when there are too many entities and relationshipsSolution: group entities and relationships into entity clustersEntity cluster: set of one or more entity types and associated relationships grouped into a single abstract entity type
33 Figure 3-13a Possible entity clusters for Pine Valley Furniture in Microsoft Visio Related groups of entities could become clusters
34 Figure 3-13b EER diagram of PVF entity clusters More readable, isn’t it?
35 Figure 3-14 Manufacturing entity cluster Detail for a single cluster
36 Packaged Data Models Predefined data models Could be universal or industry-specificUniversal data model = a generic or template data model that can be reused as a starting point for a data modeling project (also called a “pattern”)
37 Advantages of Packaged Data Models Use proven model componentsSave time and costLess likelihood of data model errorsEasier to evolve and modify over timeAid in requirements determinationEasier to readSupertype/subtype hierarchies promote reuseMany-to-many relationships enhance model flexibilityVendor-supplied data model fosters integration with vendor’s applicationsUniversal models support inter-organizational systems
38 Figure 3-15 PARTY, PARTY ROLE, and ROLE TYPE in a universal data model (a) Basic PARTY universal data modelPackaged data models are generic models that can be customized for a particular organization’s business rules
39 Figure 3-15 PARTY, PARTY ROLE, and ROLE TYPE in a universal data model (b) PARTY supertype/subtype hierarchy
40 Figure 3-16 Extension of a universal data model to include PARTY RELATIONSHIPS
41 Phase I - Logical Design Phase MVC_Hospital HWPhase I - Logical Design PhaseDraw a entity-relationship diagram (enterprise model) for Mountain View community Hospital, based on the narrative description of the case and this handout (but the entities are from the five (5) figures/reports shown above). You should create a file and turn in with a hardcopy (called MVC_PhaseI_ERD_Lname_Fname.docx) contains the following materials:1. Read and employ materials from chapters 3 and 42. Include entities, associations (with detail multiplicity), and attributes.3. Determine and draw the order of entering dataNext phase -- implementation, create SQL script file for table structure and data base (values).Upload ONLY the .docx file to the Bb.
42 MVC_Hospital Phase II. Phase III. Create two script files: (a) a script file (MVC_Hospital_Lastname_Firstname.SQL) that contains a set of commands of DROP, CREATE, and INSERT that performs the same functions as in the script file of Northwoods.sql(b) Save your spooled file (both script file and result from SQL) as MVC_PhaseII_Spool_Lastname_Firstname.LST Upload the spooled file to the Bb.Phase III.(a) Second script file (MVC_PhaseIII_QUERIES_Lastname_Firstname.SQL) containing a set of SQL commands that answer the questions. Test the query one/time successfully.Note that you may need other SQL commands and create database views for the purpose of answering questions easily. You may need to read other references related the SQL from the text book (e.g., Chapters 6 & 7 of the main text).(b) Save the spooled file as MVC_PhaseIII_Spool_Lastname_Firstname.LST. Finally, you create a new file (*.docx) containing all work done from Parts I, II and save them in the file MVC_Hospital_Complete_Lastname_Firstname.docx.(c) The file should contain your class and personal information, information for each question (re-type with question number) as well as each individual query and result.Upload ONLY the .docx file to the Bb.