UML for Data Architects

UML for Data Architects:
A Painless Introduction

Dr. Vladimir Bacvanski
vladimir.bacvanski@scispike.com

About the Speaker: Dr. Vladimir Bacvanski

 Mission: to make organizations successful in
solving problems through adoption of modern
software technologies
– Founder of SciSpike – a training and consulting firm
specializing in advanced software technologies
– Over two decades of experience with software and data
technologies
– Vladimir has helped a number of organizations
including US Treasury, Federal Reserve Bank, US Navy,
IBM, Dell, Hewlett Packard, JP Morgan Chase, Nokia,
g
Lucent, Nortel Networks, General Electric, BAE Systems,
AMD, and others
– Frequent speaker at leading industry events.
q p g y
– For three years in a row awarded the title "IBM
Information Champion" for his contributions to the
information management community
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www.scispike.com Copyright © SciSpike 2011 2

Outline

 What is UML?
 How to approach UML? (aka "Avoiding pain")
 UML diagrams: use only what you need!
g y y
 Representing structure: class (aka type) diagrams
 UML for database design
 Automation
 Conclusion


What is UML?

 The UML is a graphical language for
software intensive systems
f
– Note: UML is just a notation:
the way we visualize our decisions
h i li d ii
 UML covers a broad area of software
development
d l t
 UML is a standard: it enables you to
express your models i a way th t
d l in that
can be understood by others


Models and Diagrams

 Model is a view of a system from a particular perspective
 Diagram visually presents elements of a model
– One model can be presented with several diagrams, each
focusing on a separate aspect


UML Diagrams

Diagrams in italics are introduced in UML 2


Choose your Approach to UML!

Painful Painless

• Focus on > 95% of UML • Focus on < 5% of UML
that
th t you d 't need
don't d that
th t you need d
• Start with a 1000+ • Start with a subset
pages UML Reference relevant to data
• Avoid practical modeling
examples • Seek practical guides
• Use UML for all the and examples
wrong reasons • Use UML to
communicate and
automate


Modeling Data with UML Class Diagrams

 A subset of UML Class Diagram is very close to notations
used in d
d data modeling
d l
 UML Class Diagrams have features not needed for data
modeling:
d l
– Operations (methods)
– Visibility (public, private, …)
 We can use only a subset that make sense for data modeling:
– Classes (aka "types")
– Attributes
– Associations
– Generalization


UML Classes and Attributes
Class
Similar to entity in ERD.
Customer
Class name
Typically capitalized.

Attribute Compartment
The only compartment we care about.
UML classes can have other
compartments, e.g. for operations.
It is fine to skip parts we don't need!
pp

Note:
N t
Attribute Name Attribute Type High level class
Typically E.g. String, Integer,… diagrams typically don't
lowercase. but also other class names need primary and
foreign keys.

UML Associations
Association Association Name Multiplicity
Usually skipped. *: zero or many
1..*: one or many
0..1: zero or one

Association Role
Start from a class, follow the
Start from a class follow the Note:
association, read the role of the Foreign key attributes are
not needed
associated objects.


Navigability

1..* *
Person Address
homeAddress

 High level diagrams typically do not show navigability
 Navigability is a design decision!
– It is a bad practice to assign navigability prematurely
– Typically not needed for modeling when we target
relational databases


Associations vs. Attributes

Person
P Multiplicity
M lti li it Company
C

employer: Company[*]
p y p y[ ] employee: Person[1..*]
p y [ ]

 In UML, attributes and associations are equivalent!
 Choose the representation that is more suitable to the
reader
 Important relationships are often represented as
associations – they bring the visual emphasis


Association Class

Association
Class
Cl

 Association class allows to attach information to an
association
– Often refined into two associations to a class


Association Class Refined

 Association classes are commonly refined in lower level
y
diagrams


Semantics of Aggregation and Composition

1
Car Engine

Aggregation
1
Car Engine

Composition

 Aggregation: shortcut for "has" relationship
has
– Does not have a well defined semantics. Use sparingly!
 Composition lifetime of the owner determines the lifetime
Composition:
of the owned objects
– Similar to "cascading"
cascading

Generalization (aka Inheritance)

Employee
Generalization
G li i

Engineer Manager TechWriter

 Subclasses extend superclasses with additional attributes
and associations
 This relationship eventually needs to be mapped to tables
for relational database design
– Several solutions possible with different performance impact. Choice
impact
depends on the typical pattern of usage.

Constraints

 Constraints can be expressed as:
– Plain text
– OCL: Object Constraint Language, part of UML
• Not common in mainstream projects
• Enforcable


Organizing UML Models: Packages

 A package is a
structuring element
Customer
Management – It contains other
elements and
diagrams
Sales
 P k
Packages are important
i
for managing
complexity of models
 Prefer models organized
Inventory into packages to huge
diagrams


Mapping UML to ER Models…

 Class  Entity
– Add primary key
 Simple Attribute Type  Column Type
 Complex Attribute Type  Relationship to an entity for the
attribute type
 Association  Foreign Key relationships
– Use role names for foreign keys
– Many-to-many association  add an associative table
– Aggregation: treat as ordinary relationships


…Mapping UML to ER Models

 Generalization: use the usual mappings:
– Table per class hierarchy
– Table per subclass
– Table per concrete class
 Constraints
– Set constraints on the database
– Some only enforceable in application logic
y pp g

This is just a simplified set of rules to get you going!


UML for Database Design

 Agile teams often use UML for both software and database
design
 UML data modeling profile introduces extensions to UML:
– <<PK>>, <<FK>>, <<Auto Generated>>, <<Not Null>>,
<<View>>, <<Stored Procedures>>,…
 Use relational data types
– String  CHAR(x), VARCHAR(x)


Automation

Code

Transformer
DDL

Input
Models
Models
Output

 Tools can convert from UML to ERD and vice versa
 Model transformation tools operate at a MOF/EMF level and
can transform UML to various targets
– Visual Domain Specific Languages (DSLs) based on UML may provide
better alignment with the p
g problem domain than vanilla UML


Conclusion

 You will need just a small part of UML!
 UML is a common starting point for data models
 Mapping of UML to ER is quite straightforward
pp g q g
 Knowing UML makes you a more significant player in the
software development p
p process


Getting in Touch

 Email: vladimir.bacvanski@scispike.com
 Blog: http://www.OnBuildingSoftware.com/
 Twitter: http://twitter.com/OnSoftware
p
 LinkedIn: http://www.linkedin.com/in/VladimirBacvanski

 SciSpike Training and Consulting:
http://www.scispike.com
http://www scispike com
– Related training for data architects:
• Visual Modeling with UML
• Mastering Data Modeling with InfoSphere Data Architect


UML for Data Architects

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