UML and Data Modeling - A Reconciliation

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UML and Data Modeling - A Reconciliation

  1. 1. Yes, You Can Create An Architectural Data Model In UML The Handbook DAMA Midwest Chapters October, 2012 David C. HayEssential Strategies, Inc.13 Hilshire Grove Lane, Houston, TX 77055(713) 464-8316dch@essentialstrategies.com 1www.essentialstrategies.com Copyright © 2011, Essential Strategies, Inc. 1/99
  2. 2. Today’s theme . . . A man may be a topologist or an acoustician or a coleopterist. He will be filled with the jargon of his field, and will know all its literature and all its ramifications. . . . . .but, more frequently than not, he will regard the next subject as something belonging to his colleague three doors down the corridor, and will consider any interest in it on his own part as an unwarrantable breach of privacy. These specialized fields are continually growing and invading new territory. The result is like what occurred when the Oregon country was being invaded simultaneously by the United States settlers, the British, the Mexicans, and the Russians—an inextricable tangle of exploration, nomenclature, and laws. Norbert Wiener, Cybernetics; 1948.11 Norbert Wiener. 1948, 1961. Cybernetics: of Control and Communication in the Animal and the Machine, second edition. (Cambridge, MA, The MIT Press). 2. Copyright © 2011, Essential Strategies, Inc. 2/99
  3. 3. An inextricable tangle of…nomenclature… For example, data modeling and UML Data Modelers  UML Modelers Copyright © 2011, Essential Strategies, Inc. 3/99
  4. 4. An inextricable tangle of…nomenclature… For that matter, within data modeling . . .  Database  Conceptual Data Designers Modelers 4 4/99 Copyright © 2011, Essential Strategies, Inc.
  5. 5. Some history . . . Pre 1960 Card decks, magnetic tape Pre 1960 Fortran / COBOL Mid 1960s 1st DBMS 1967 Simula 67 1970 Ted Codd - Relational theory 1970 Structured Design 1976 Peter Chen – Data models 1978 Data flow diagrams 1978 Relational Databases 1981 Information 1980 The Personal Computer Engineering, Barker/Ellis 1980 Small Talk / C++ 1987 Zachman Framework 1988 Object-oriented Analysis 1990s Data Management 1991 Object Modeling 1990s Business Rules 1992 Use Cases 1995 Data Model Patterns 1995 Java 1995 Design Patterns 1997 UML Copyright © 2011, Essential Strategies, Inc. 5/99
  6. 6. About the Unified Modeling Language (UML)  Created in 1997, UML is an array of notations for modeling  Classes,  Activities,  State Machines  Use Cases  Interactions  It is intended to support object-oriented program design. Today .we only care about these.  Note that by the late 1990s, outside the object-oriented community, modeling to support requirements analysis was already well established :  Entity/relationship models (classes)  Data flow diagrams (activities)  State/transition diagrams (state machines)  Entity life histories (entity type behavior) Copyright © 2011, Essential Strategies, Inc. 6/99
  7. 7. About Data Modeling . . . As stated, There are two groups of data modelers:  Group one creates logical data models to support database design.  Group two creates architectural data models to represent the structure of the business, independent of database technology. Copyright © 2011, Essential Strategies, Inc. 7/99
  8. 8. Group one (DB designers) finds UML annoying because . . . The orientation is different:  Database administrators: data as an asset, to be protected  UML (OO) Designers: data as a support to programs. Relational structures deal badly with inheritance  (and OO people have “attitudes”…). Copyright © 2011, Essential Strategies, Inc. 8/99
  9. 9. Group two (business modelers) find UML annoying because . . . UML is not constrained in defining what is a “class”. UML (as practiced) has a very peculiar way of naming relationships. UML notation and practices are not conducive to presenting models to the business. element ownership 0..* Classifier Field 1..1 Copyright © 2011, Essential Strategies, Inc. 9/99
  10. 10. So . . . Does UML supersede data modeling? Some would say no… Since it is about object oriented design… … it is not suitable for business analysis. Copyright © 2011, Essential Strategies, Inc. 10/99
  11. 11. Problem: UML is. . . HERE  Despite its flaws, The Unified Modeling Language has been recognized as a standard in many quarters.  Clients and hiring managers keep asking if you have experience with UML. !!! How should we entity/relationship dudes deal with this? Copyright © 2011, Essential Strategies, Inc. 11/99
  12. 12. It’s easy . . . Just build your entity / relationship models in UML! So I did . . . Copyright © 2011, Essential Strategies, Inc. 12/99
  13. 13. Which meant that . . .  My data modeling colleagues were convinced that I had completely sold out and gone over to the dark side . . .  . . . and my UML/object modeling colleagues accused me of bastardizing their sacred notation. So, I wrote another book in response . . . Copyright © 2011, Essential Strategies, Inc. 13/99
  14. 14. A companion volume . . .  Two audiences:  Data modelers convinced that UML has nothing to do with them.  UML modelers who don’t realize that architectural data modeling really is different …  … and the differences are important.  This is a handbook on how to use the UML class notation to produce an Architectural Entity / Relationship diagram. Copyright © 2011, Essential Strategies, Inc. 14/99
  15. 15. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 15/99
  16. 16. Today’s Program Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 16/99
  17. 17. Ok, let’s be honest . . . Data modelers themselves are sometimes a bit free-wheeling about what constitutes a class. Data modelers are often not as disciplined in making business structures presentable as they might be. Data modelers can be very casual in naming relationships 17/72 Copyright © 2011, Essential Strategies, Inc. 17/99
  18. 18. Not so Hidden agenda: Present the characteristics of a high quality architectural data model… …no matter what notation is used.18/72 Copyright © 2011, Essential Strategies, Inc. 18/99
  19. 19. Specifically, This Presentation . . . Will show the business-oriented modelers how to accomplish their objectives in UML. Will show the database designers how to do business-oriented modeling in UML. Will show UML object modelers how to bring business-oriented modeling into UML. (UML as a database design notation is for another presentation.) 19/72 Copyright © 2011, Essential Strategies, Inc. 19/99
  20. 20. After the book was published, I learned that . . .  My version of UML is something the OMG calls a “domain specific language” for entity/relationship modeling.  It even gets an acronym: “DSL”.  I knew I was tinkering with the language,  …but I didn’t realize it was something! Copyright © 2011, Essential Strategies, Inc. 20/99
  21. 21. Today’s Program  Objectives Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 21/99
  22. 22. Kinds of data models . . .  We modeling types are quick to criticize our clients for getting their vocabularies confused.  But what about us? What do we mean by . . .  “Conceptual” data model?  “Logical” data model?  “Physical” data model?  “Semantic” data model?  And now you’re adding “Architectural” data model?  For purpose of this presentation, here are the definitions: After all, it is my presentation… Please hear me out… Copyright © 2011, Essential Strategies, Inc. 22/99
  23. 23. Kinds of Models . . . Corporate Overview: Context for executive management, strategies. (Planner’s View) (Not “Conceptual”) Conceptual: Business-oriented, but in detail; technologically neutral. Two flavors:  Semantic: In language of business owner; divergent. (Business Owner’s View)  Architectural: Abstract, encompassing multiple groups: convergent (Architect’s View) (Not “Logical”) Logical: In terms of data management technology. (Designer’s View) (Not “Physical”) Physical: In terms of physical storage devices— table spaces, partitions, etc. (Builder’s View) Copyright © 2011, Essential Strategies, Inc. 23/99
  24. 24. Context: ANSI’s Three ways to look at data.(1975) . . . Four .. External Schema Logical Internal Schema Schema (Relnl.) Conceptual Logical Schema Internal Schema External Schema (XML) Schema 2 External Schema 3 Physical Schema Physical Schema Copyright © 2011, Essential Strategies, Inc. 24/99
  25. 25. The Architecture Framework . . . Data Activities Network People Timing Motiva- (What) (How) (Where) (Who) (When) tion (Why) List of Organi- Business Objectives/ Scope Important List of Business zational Units Events, Business Vision Processes Locations and Mission Things Cycles Business Operations Org. Chart, Master Business Policies Business Owner’s Terms, Process by Business Roles Business and Rules View Definitions Model Location Schedule Entity/ Data Links, Roles+Data State/ Essential Business Rule Architect’s View Relationship Functions Processing (Use Cases) transactions, Model Diagram Locations ELH Network User Interface, “Control Flow” Designer’s Tables, System Architecture Security diagrams Rule Design View Classes Design (h/w, s/w types) Data, physical Detailed Screens, storage design Network Timing Rule Specification Builder’s View Program Construction Security Definitions Design Design Functioning Working System System Copyright © 2011, Essential Strategies, Inc. 25/99
  26. 26. The Architecture Framework . . . Data Activities Network People Timing Motiva- (What) (How) (Where) (Who) (When) tion (Why) List of Business List of Business Organizational Business Vision Executive’s View Important Processes Locations Units Events, and Mission Things Cycles Business Owner’s Operations Master Terms, Business Org. Chart, Business Policies by Business Business View Definitions Processes Roles and Rules Location Schedule Data Links, State/ Entity types, Essential Roles+Data Business Rule Architect’s View Relationships Functions Processing (Use Cases) transactions, Definitions Locations ELH Tables, Network System User Interface, “Control Flow” Designer’s OO Classes Design Architecture Security diagrams Rule Design XML tags (h/w, s/w types) View Physical Detailed Screens, Network Timing Rule Builder’s View Storage, Program Construction Security Definitions Implementations Programs Design Design Functioning Working System System Copyright © 2011, Essential Strategies, Inc. 26/99
  27. 27. In terms of the Architecture Framework . . . Logical Model Architectural (Row 4) Model (Row 3) External Schema 1 Logical Schema (Relnl.) Conceptual Logical External Schema Schema Schema 2 (XML) External Schema 3 Physical Physical Physical Model Schema Schema Semantic Model (Row 5) (Row 2) Copyright © 2011, Essential Strategies, Inc. 27/99
  28. 28. Ok, let’s look into the data column more deeply…Copyright © 2011, Essential Strategies, Inc. 28/99
  29. 29. Business Owners’ Semantic Data Terms, concepts. Views Model, definitions (Semantics) (E/R, SBVR, OWL) Architectural “Conceptual” Entity/Relationship Data Model ModelArchitect’s View Entity types, (Integration of Architectural attributes,Business Owners’ Data Model relationships Views) Database Object-oriented Design Design Model Model (UML) Tables, columns, Object-oriented XML keys Designer’s View RELATIONAL DATA BASES Classes Schemas Classes, attributes, (Technology) associations Tags Copyright © 2011, Essential Strategies, Inc. 29/99
  30. 30. Today’s Program  Objectives  Kinds of Models (and what we call them) Introduction to UML  Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 30/99
  31. 31. UML was originally designed to support object-oriented design… …not architectural business modeling.But do I have a deal for you . . . Copyright © 2011, Essential Strategies, Inc. 31/99
  32. 32. We can use UML for a data model?  Yes…but with restrictions:  Restrict the definition of entity type.  Use a subset of the notation.  Recognize that E/R relationships are not the same as OO associations.  Pay attention to Layout aesthetics.  Add unique identifiers. Copyright © 2011, Essential Strategies, Inc. 32/99
  33. 33. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 33/99
  34. 34. Kinds of Notations . . .  Of interest to us . . .  Information Engineering – Most commonly used among data modelers.  Barker / Ellis – Most technologically independent  UML – The subject of today’s talk  Not of interest to us . . .  IDEF1X – Buried in relational design  Object Role Modeling – Different approach  OWL – Future presentations Copyright © 2011, Essential Strategies, Inc. 34/99
  35. 35. E/R Notation (Information Engineering) . . . Maximum Cardinality Attribute Minimum Cardinality Line Item Order Line Number part of Order Number Order Number (FK) composed of Order Date Quantity Price (Extended Value) Delivery Date Role Name entity type Identifiers Relationship Line Item_1 Order_1 Line Number part of Order Number Order Number (FK) Order Date composed of Quantity Price (Extended Value) Delivery Date Copyright © 2011, Essential Strategies, Inc. 35/99
  36. 36. E/R Notation (Information Engineering) . . .  Shows cardinality as graphics. Observer sees it.  Shows identifying attributes and relationships.  Identifying attributes in separate section of entity type box.  Identifying relationship through combination of symbols:.  NOTE: Each relationship direction is structural, representing an assertion about the nature of the domain.  Minimal references to technology…  … but there is a relational design bias:  Foreign keys implementing relationships  Complexity of identifying relationships. Copyright © 2011, Essential Strategies, Inc. 36/99
  37. 37. E/R Notation (Barker-Ellis) . . . Maximum Attributes Cardinality Minimum Cardinality Role Names entity type Relationship Identifiers Copyright © 2011, Essential Strategies, Inc. 37/99
  38. 38. E/R Notation (Barker-Ellis)  Shows cardinality as graphics. Observer sees it.  Shows identifying attributes and relationships with simple symbol.  NOTE: Each relationship direction is structural, representing an assertion about the nature of the domin.  No references to database or any technology. Copyright © 2011, Essential Strategies, Inc. 38/99
  39. 39. UML Notation . . . Maximum CardinalityAttributes Minimum Cardinality ..1 Class Role Names Relationship (Association) Identifiers (None) Copyright © 2011, Essential Strategies, Inc. 39/99 39/
  40. 40. UML Notation . . .  Systematic cardinality notation (attributes and associations).  Cardinality textual, not graphic. Viewer must read and understand it.  MAJOR ISSUE: In UML, an association is a navigation path, not a structure.  Identifier notation added in version 2.2. (Can also be added via “stereotypes”.)  No database connection . Full notation has object-oriented design symbols  …that we can ignore. Copyright © 2011, Essential Strategies, Inc. 40/99
  41. 41. About Notations . . .  Different notations (as implemented via different tools) make it easier or more difficult to do certain things.  The important dimension is good practices.  Best to support the practices here is Barker / Ellis  Second best is the revised version of UML.  Information Engineering’s bias toward relational database design is hard to thwart. But it is the best practices, not the notation that is most important. Copyright © 2011, Essential Strategies, Inc. 41/99
  42. 42. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations About Classes  About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 42/99
  43. 43. According to the “Three Amigos” . . .  An object is a “discrete entity with a well-defined boundary and identity that encapsulates state and behavior; an instance of a class”  A class, in turn, is “the descriptor for a set of objects that share the same attributes, operations, methods, relationships, and behavior.”1 Note: No constraints as to what kinds of objects or classes were of interest. 1 Rumbaugh, J., Ivar Jacobson, Grady Booch. 1999. The Unified Modeling Language Reference Manual. p. 360. Copyright © 2011, Essential Strategies, Inc. 43/99
  44. 44. According to James Martin and James Odell, “anything is an object”.22. Martin, J., and James Odell. 1995. Object-Oriented Methods. (Englewood Cliffs, NJ: Prentice Hall). p. 34. Copyright © 2011, Essential Strategies, Inc. 44/99
  45. 45. An “Entity” on the other hand . . .  … is not just any “discrete entity with a well-defined boundary and identity”.  … is limited to what Richard Barker calls things or objects “of significance, whether real or imagined, about which an organization needs information.”3  An “entity type”, unlike other “classes”, is not concerned with operations, methods, or behavior.  Those belong to the world of “process modeling.”  An entity/relationship model is only concerned with the Structure of business data. 3. Barker, Richard. 1990. CASE*Method: Entity Relationship Modeling. (Wokingham, England: Addison-Wesley). Copyright © 2011, Essential Strategies, Inc. 45/99
  46. 46. About language in the model . . .  An architectural entity/relationship diagram is essentially a graphic portrayal of English language assertions about an organization. *  Therefore, the only language to appear on a diagram must be in terms relevant to the domain of interest.  Only business terms (and conventional English) may be used as the names of entity types, attributes, and the names of roles.  That is, no abbreviations, computer terms, or acronyms.  Words are not concatenated together. Spaces between words are shown (“Line Item”, not “lineItem”). * … or assertions in any other natural language, such as Polish, French, Chinese, or what have you. Copyright © 2011, Essential Strategies, Inc. 46/99
  47. 47. Entity Type names . . .  The name of an entity type is in the singular, and refers to an instance of that class.  Hence, Order and Line Item are acceptable.  The name “Project history” is not.  An entity type called Project, on the other hand, could contain instances over time, so it may in fact be a project “history”  Database table names are not allowed, nor are abbreviations or acronyms.  Classes that are computer artifacts (“window”, “cursor”, and the like) are not allowed. Copyright © 2011, Essential Strategies, Inc. 47/99
  48. 48. Again, because the model will bepresented publically, spaces between words are required. Copyright © 2011, Essential Strategies, Inc. 48/99
  49. 49. Naming Attributes . . .  In both E/R and UML an attribute is a characteristic of an entity type.  It “serves to qualify, identify, classify, quantify, or express the state of an entity” 4  In the previous example:  Order: “Order number” and “Order date”.  Line Item: “Line number”, “Quantity”, “Price”, “Delivery date”, and “/Extended value”.  “/” means a derived attribute. *  /Extended value = Quantity * Price  Again, spaces are required (where appropriate). (“Delivery Date”, not “deliveryDate”) 4, Barker, op. cit., p. 5-6.* This is something UML has over E/R notations. Copyright © 2011, Essential Strategies, Inc. 49/99
  50. 50. Cardinality of attributes . . . In UML, cardinality is represented the same way for attributes as for roles.  Minimum cardinality: [1..1] – Mandatory: must be at least one value; may be no more than one value. Usually abbreviated “[1]”. [0..1] – Optional: may or not have a value; may have no more than one value.  Maximum cardinality must always be ..1. Multi-valued attributes are not permitted. Copyright © 2011, Essential Strategies, Inc. 50/99
  51. 51. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes About Relationships  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 51/99
  52. 52. Associations / Relationships . . .  Each E/R relationship is a structure composed of two roles.  Each role is an English language assertion * about the domain of discourse:  Each – (The assertion is about each instance of the first entity type.)  Subject – (The first entity type)  Minimum cardinality (“must be” or “may be”)  Predicate – (The role name)  Maximum cardinality (“one or more” or “one and only one”)  Object – (The second entity type).* …or Spanish or French or Polish or whatever. The point is that it must be in a natural language, not in computer jargon. Copyright © 2011, Essential Strategies, Inc. 52/99
  53. 53. For example (E/R notation) . . . Order Party Order Number Party ID from customer in to vender in 1. Each Order must be from one and only one Party. 1a. Each Party may be a customer in one or more Orders. 2. Each Order must be to one and only one Party. 2a. Each Party may be a vendor in one or more Orders. These are assertions about the nature of the enterprise. Copyright © 2011, Essential Strategies, Inc. 53/99
  54. 54. UML looks at it differently . . .  An association is a path, not a structure.  Because 2nd class is not in 1st class’s namespace, it cannot be part of the property of the 1st class.  Hence roleName is simply a label for the second class (a noun). Role name often simply copies the 2nd class name.  (In this case, role name does distinguish two roles.)  Role name is not part of a structural statement. Copyright © 2011, Essential Strategies, Inc. 54/99
  55. 55. UML looks at it differently . . . 1. Each Order must be related to one and only one thing that is labeled “customer”. 1A. Each Party may be related to one or more things that are labeled “purchase order”. 2. Each Order must be related to one and only one thing that is labeled “vendor”. 2a. Each Party may be related to one or more things that are labeled “sales order”. Copyright © 2011, Essential Strategies, Inc. 55/99
  56. 56. Changes to the “standard” UML approach . . .  Role names are prepositions  Preposition is the part of speech that describes relationships.  Nouns describe things. The entity types are already the things.  (…and they are already labeled.)  No duplication of the entity type name in the role name.  To duplicate the class name is a serious redundancy in UML.  The practice comes from requirements of Java programming: The object class is not part of the subject class’s “namespace”.) Copyright © 2011, Essential Strategies, Inc. 56/99
  57. 57. About reading the role names . . . For example . . . Each primarily 0..* Book <entity class 1> Book about Topic of 1..1 1..* 1.. must be (or) Each Book must be primarily 0.. may be about one and only one Topic. one or more primarily about <role name> Each Topic may be of one or more Books. ..1 one and only one (or) ..* one or more But is this true? Topic <entity class 2> Many books are about more than one topic. Copyright © 2011, Essential Strategies, Inc. 57/99
  58. 58. Following correct rulesof modeling helps lead to the truth. Determining the truth of the model is a different exercise. Copyright © 2011, Essential Strategies, Inc. 58/99
  59. 59. Role names are important . . . ‘Ravenous Bugblatter Beasts often make a very good meal for visiting tourists’ Copyright © 2011, Essential Strategies, Inc. 59/99
  60. 60. This should have read . . . “Ravenous Bugblatter Beasts often make a very good meal of visiting tourists” Douglas Adams. 1982. The Restaurant at the End of the Universe. New York: Pocket Books, pp. 37– 38. Copyright © 2011, Essential Strategies, Inc. 60/99
  61. 61. A word about conversion . . . “Conversion”, not simply “more detail”. - John Z. Copyright © 2011, Essential Strategies, Inc. 61/99
  62. 62. For example, conversion to a Database Design . . . Order Party Order_Number Party_ID Customer (FK) Vendor (FK) from to Copyright © 2011, Essential Strategies, Inc. 62/99
  63. 63. The UML Design Version . . .  Similarly, an architectural UML model must also be converted to an object-oriented program model: E/R role names are converted to OO roleNames as: “predicate|object class name”. Copyright © 2011, Essential Strategies, Inc. 63/99
  64. 64. Thus, conversion to an Object-oriented Design . . . Copyright © 2011, Essential Strategies, Inc. 64/99
  65. 65. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes  About Relationships About Domains  Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation 65/99 Copyright © 2011, Essential Strategies, Inc.
  66. 66. Domains . . .  In E/R modeling, a domain is “A set of business validation rules, format constraints, and other properties that apply to a group of attributes”.  For example:  a list of values  a range  a qualified list or range  any combination of these.  “Note that attributes and columns in the same domain are subject to the same validation checks.” 5 5. Barker, op. cit. p. G1-3. Copyright © 2011, Essential Strategies, Inc. 66/99
  67. 67. Code lists . . .  In database design, a code list is a set of valid values for a column.  For example, the column “STATE_ABBR” may be controled by the code list “State abbreviations”. This would have the values “AL”, “AK”, “AZ”, etc. This is one code list that implements the domain “State” Others might be “State official name”, “State code”, etc.  In database design, a validation rule may control the legal values for a column.  For example, the column SALARY may be constrained by the validation rule “Positive number”. That is, the value must be greater than zero. Copyright © 2011, Essential Strategies, Inc. 67/99
  68. 68. Data type . . .  Each E/R domain must also in turn specify the data type of the values for a referenced attribute.  These include:  String  Number  Date  Boolean  Etc. Copyright © 2011, Essential Strategies, Inc. 68/99
  69. 69. Data Types as Domains . . .  In addition to the standard data types that come with UML (“number”, “string”, etc), it is possible to define new data types to address any validation criterion desired.  “Social security number”  “Telephone number”  Etc. Copyright © 2011, Essential Strategies, Inc. 69/99
  70. 70. Enumeration in UML  UML takes a different approach to both code lists and domains.  A code list may be described explicitly as an enumeration.  This looks like an “entity type”, but instead of showing the attributes “Code” and “Definition”, it shows the list of values. Copyright © 2011, Essential Strategies, Inc. 70/99
  71. 71. Today’s Program  Objectives  Kinds of Models (and what we call them)  Notations  About Classes  About Relationships Unique Identifiers  Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 71/99
  72. 72. In 2011, the OMG got the message . . .  Originally, the object-oriented community assumed that all classes are identified by a surrogate key, called an object identifier  Until recently, UML has no inherent facility for representing natural unique identifiers.  With version 2.2, there is now a “property” called “isID?”  It is displayed on the drawing as {id}  This version exactly maps to the stereotypes, and is much simpler than the Information Engineering approach. Copyright © 2011, Essential Strategies, Inc. 72/99
  73. 73. Today’s Program  Objectives  Kinds of Models (and what we call them)  Notations  About Classes  About Relationships  Unique Identifiers Unnecessary in UML  Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 73/99
  74. 74. Unnecessary UML features . . .  UML was developed to support object-oriented design.  Some of its features are not meaningful in an entity/relationship diagram.  Navigation  Visibility  Composition Copyright © 2011, Essential Strategies, Inc. 74/99
  75. 75. Navigation  In an Entity/Relationship diagram, a relationship describes structure.  By definition both ends and both roles must exist. (You cannot build half a bridge.)  In an object-oriented program, program code must be written to get from one class to another.  If the application only calls for navigating in one direction only, it is useful (for the developer) if the designer indicates that. This is not part of an Entity/Relationship diagram. Copyright © 2011, Essential Strategies, Inc. 75/99
  76. 76. Visibility . . .  In an object-oriented program, attributes of a class may be “visible” only to that class, or to super-types of that class, or to the entire application.  This is shown by: This is not part of an  A “+” sign for universally visible” Entity/Relationship  A “-” sign for restricted visibility. diagram.  A “#” sign for protected visibility.  A “~” for visibility within a package. Copyright © 2011, Essential Strategies, Inc. 76/99
  77. 77. Composition . . .  Within object-oriented programs, composition structure is very common and very important.  So a symbol ( ) is equivalent to the role name “composed of”.  This includes the referential integrity constraint “cascade delete”.  Another symbol ( ) is also “composed of”, but this enforces the the referential integrity “nullify”. Copyright © 2011, Essential Strategies, Inc. 77/99
  78. 78. Composition . . .  Entity / Relationship modeling addresses the semantics of the business with language.  Another symbol for the words “composed of” is redundant.  Can’t do referential integrity anyway (There is no symbol for “Restricted Delete”). Copyright © 2011, Essential Strategies, Inc. 78/99
  79. 79. Today’s Program  Objectives  Kinds of Models (and what we call them)  Introduction to UML  Notations  About Classes  About Relationships  Unique Identifiers  Unnecessary in UML Aesthetics and Presentation Copyright © 2011, Essential Strategies, Inc. 79/99
  80. 80. How to be Effective . . .  The first objective of a data model is presentation to a non- technical audience. This requires:  Effective use of language  Good aesthetics  Effective presentation Copyright © 2011, Essential Strategies, Inc. 80/99
  81. 81. How to be Effective – Language . . .  The first objective of a data model is presentation to a non-technical audience. This requires:  Effective use of language  Business terms for entity types.  Business assertions for relationships.  Good aesthetics  Sub-type boxes inside super-type boxes  No more than 10-12 boxes per page.  Straight lines.  “Dead crows” positioning. (OK, “starry skies”…)  Effective presentation  A succession of diagrams  Each adding 2-4 entity types. Copyright © 2011, Essential Strategies, Inc. 81/99
  82. 82. How to be Effective – Principles of Aesthetics . . .  The first objective of a data model is presentation to a non- technical audience. This requires:  Effective use of language  Good aesthetics Sub-type boxes inside super-type boxes No more than 10-12 boxes per page. Straight lines. “Dead crows” positioning. (OK, “starry skies”…)  Effective presentation Copyright © 2011, Essential Strategies, Inc. 82/99
  83. 83. These principles areindependent of notationOK, some are harder to carry out, given tool limitations. Copyright © 2011, Essential Strategies, Inc. 83/99
  84. 84. Sub-types: The UML (and IE) approach . . . Copyright © 2011, Essential Strategies, Inc. 84/99
  85. 85. The Barker-Ellis approach . . . PARTY PERSON  More compact.ORDER from # PERSON ID# ORDER NUMBER* ORDER DATE the source of * o FIRST NAME MIDDLE INITIAL  Makes it clear that * SURNAME attributes and to ORGANIZATION relationships of super- the destination of # ORGANIZATION NAME type also apply to the INTERNAL sub-type. ORGANIZATION * INTERNAL ORG TYPE  “Each Company may GOVERNMENT be the source of one or more Orders.” COMPANY  “Each Household may be the source of one or GOVERNMENT more Orders.” AGENCY POLITICAL ORGANIZATION HOUSEHOLD Copyright © 2011, Essential Strategies, Inc. 85/99
  86. 86. The E/R UML Approach . . . Copyright © 2011, Essential Strategies, Inc. 86/99
  87. 87. About the drawings . . .  No bent lines.  Orient boxes so “many” side of relationships is up or to the left. (“Starry skies” approach)  Each subject area must fit on one page.  No more than 12-15 boxes  Less than 10 is better Copyright © 2011, Essential Strategies, Inc. 87/99
  88. 88. Before . . . Copyright © 2011, Essential Strategies, Inc. 88/99
  89. 89. With Straight Lines . . . Copyright © 2011, Essential Strategies, Inc. 89/99
  90. 90. After . . . Copyright © 2011, Essential Strategies, Inc. 90/99
  91. 91. How to be Effective - Presentation . . .  The first objective of a data model is presentation to a non- technical audience. This requires:  Effective use of language  Good aesthetics  Effective presentation Build up presentation a few entity types at a time. • Start with one or two entity types. • Add one or two • And so forth For each slide, highlight what is new on that slide. Copyright © 2011, Essential Strategies, Inc. 91/99
  92. 92. About the Presentation . . .  Build up presentation a few entity types at a time.  Start with one or two entity types.  Add one or two  And so forth  For each slide, highlight what is new on that slide. Copyright © 2011, Essential Strategies, Inc. 92/99
  93. 93. Samples . . . Copyright © 2011, Essential Strategies, Inc. 93/99
  94. 94. Photo to generate interest . . . Copyright © 2011, Essential Strategies, Inc. 94/99
  95. 95. Tests . . . Copyright © 2011, Essential Strategies, Inc. 95/99
  96. 96. Observations . . . Copyright © 2011, Essential Strategies, Inc. 96/99
  97. 97. Display of test results . . . Copyright © 2011, Essential Strategies, Inc. 97/99
  98. 98. Expected Observations . . . Copyright © 2011, Essential Strategies, Inc. 98/99
  99. 99. Remember this . . . ? Copyright © 2011, Essential Strategies, Inc. 99/99
  100. 100. Conclusions . . .  UML can be used to represent architectural entity/relationship diagrams, with constraints:  Orientation toward the domain of discourse (problem domain).  Addressing only classes of significance to the business.  Changing the syntax of role names.  Addressing the aesthetics of the models.  Data model quality is a function of:  Clarity of thought  Clarity of presentation Data model quality is not a function of the notation selected Copyright © 2011, Essential Strategies, Inc. 100/99
  101. 101. Questions . . . ? And now for a bigger example . . . Copyright © 2011, Essential Strategies, Inc. 101/99

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