1. Introduction to modeling
ER modelling Slides for this part are based on Chapters 8 from Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition (ISBN: ), published by Morgan Kaufmann Publishers.

2. Where are we? # Title Date 1 Introduction 01.10.2014 2
General concepts 3
ORM modeling 4
Relational modeling 5
ER modeling 6
OO modeling 7
Services and Process modeling 10
Exam

3. Intro
ER models business domains in terms of entities that have attributes and participate in relationships
Very popular data modeling approach for databases
Originally proposed by Peter Chen in 1976
Material on this slide based on Ch 8.1 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

4. Building blocks: entities, relationships, and attributes
Barker notation
Building blocks: entities, relationships, and attributes
Attributes:
“#” indicates that the attribute is, or is a component of, the primary identifier of the entity type
“*” indicates that the attribute is mandatory
“°” indicates the attribute is optional
Relationships are restricted to binaries 
A solid half-line denotes a mandatory role, and a dotted half-line indicates an optional role
Crow’s foot notation is used for cardinality; intuitively indicates “many”, by its many “toes”; the absence of a crow’s foot intuitively indicates “one”
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

5. Barker notation (cont’)
ER diagram (a) and its equivalent to ORM (b)
Verbalization: Each A (must | may) be R (one and only one B | one or more B-plural-form)
Each Employee must be an occupier of one and only one Room; Each Room may be occupied by one or more Employees.
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

6. Equivalent Barker ER and ORM diagrams
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

7. Equivalent Barker ER and ORM diagrams
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

8. Composite identification in Barker ER
A bar “|” across one end of a relationship indicates that the relationship is a component of the primary identifier for the entity type at that end.
Composite identification in (a) Barker ER and (b) ORM
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

9. Other constraints in Barker ER
Exclusion constraints are shown as an “exclusive arc” connected to the roles with a small dot or circle
Mutually exclusive and disjunctively mandatory constraints uses the exclusive arc, but each role is shown as mandatory (solid line)
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

10. Other constraints in Barker ER
Subtyping is depicted with a version of Euler diagrams.
Material on this slide based on Ch 8.2 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

11. Barker ER notation – summary
Material on this slide based on Ch 8.3 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

12. Barker ER notation – summary
Material on this slide based on Ch 8.3 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

13. Information Engineering (IE) Notation
Different versions exist, no single standard
Supported by many data modeling tools very popular notation for database design
Material on this slide based on Ch 8.3 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

14. Equivalent constraint patterns in IE and ORM
Material on this slide based on Ch 8.3 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

15. Equivalent constraint patterns in IE and ORM
Material on this slide based on Ch 8.3 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

16. IDEF1X notation overview
Material on this slide based on Ch 8.4 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

17. ERmap – Mapping from ORM to ER
Material on this slide based on Ch 8.5 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

18. Some examples of ERmap steps
Material on this slide based on Ch 8.5 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition

19. Some remarks on ER vs ORM
In general, attribute-free approaches have advantages for conceptual analysis, including simplicity, stability, and ease of validation
Attributes allow compact diagrams that directly represent the implementation data structures (e.g., tables or classes).
Compact yet still high level view of the business domain
But whether some fact ends up in the design as an attribute should not be a conceptual issue
Attribute-free approaches offer greater semantic stability
If one models a feature as an attribute and finds out later that something needs to record about it, it needs to be remodel as an entity type or relationship because attributes can’t have attributes or participate in relationships
ORM models facilitate validation by both verbalization and population
Attributes make it awkward to use sample data populations
ER models are further removed from natural language and may be harder for the domain expert to conceptualize
Ternary vs binary relationships: an n-ary association may always be transformed into binaries, however this may introduce an object type that appears artificial to the domain expert
In general ER notations are less expressive than ORM for capturing constraints or business rules

20. Resources
Chapter 8 in Halpin, T. & Morgan, T. 2008, Information Modeling and Relational Databases, Second Edition (ISBN: ), published by Morgan Kaufmann Publishers. 
Richard Barker, Case*Method: Entity Relationship Modelling (1990), published by Addison-Wesley Professional
Tools:
RISE Editor: 
Calligra Flow: 
Dia: 

21. Next lecture # Title Date 1 Introduction 01.10.2014 2 General concepts 3
ORM modeling 4
Relational modeling 5
ER modeling 6
OO modeling 7
Services and Process modeling 10
Exam

22. Questions?