LIST
Lightning Talk: The Distributed Human System - Alan Jefferies distributed computer systems flow Definition: distributed systems -– backlogs implicit in this definition i make explicit: decentralize control homan historically - assumption: partition tolerance is not important in human systems -we work from the same office anyway UNTIL: 2 nasty viruses we got partitioned ...
Lightning Talk: What do you mean by “is”? - Duncan Jones (1) ignition switch variable (2) car (3) traffic it depends can only answer what the answer “was” transactions: it’s bad form to lock guests in their room Example: distance (influences time) business rule containing “is” do you mean - quite recently - a minute ago, 5 minutes ago - defined location (priveleged observer)
Search for ’natural folding lines’ in the domain Try to find the “natural folding lines” between areas in the domain. how: ask domain experts: “Can you imagine that changing data x ever impact data y” eg. “[hospital] Would the patient changing family name impact which doctor they get treated by” eg. “[webshop] Would changing the description of a product cause the price to change?” When the domain expert looks at you like - "You don't get it at all do you?...
I have found multiple ways of looking at this: behaviour vs methods behaviour vs state behaviour vs implementation (1) Unit-Test Behaviour, Not Methods focus on the features that the object under test should provide, We need to know how to use the class to achieve a goal, not how to exercise all the paths through its code. Describing Behavior, Not API Features We need to know how to use the class to achieve a goal, not how to exercise all the paths through its code....
Heuristic: Composite Simpler Than the Sum of Its Parts hides enough information moneyEditor.getAmountField().setText(String.valueOf(money.amount()); moneyEditor.getCurrencyField().setText(money.currencyCode()); moneyEditor.setAmountField(money.amount()); moneyEditor.setCurrencyField(money.currencyCode()); moneyEditor.setValue(money); (src: Book_ Growing Object Oriented Software, Guided By Tests - Steve Freeman & Nat Pryce)
Heuristic: Context Independence hides too much / wrong information whatever an object needs to know about the larger environment it’s running in must be passed in permanent relationships (constructor argument) transient relationships (method argument) (src: Book_ Growing Object Oriented Software, Guided By Tests - Steve Freeman & Nat Pryce)
Model: 2 layers in Higher-Level Programming implementation layer declarative layer a declarative layer emerges from continual “merciless” refactoring (src: Book_ Growing Object Oriented Software, Guided By Tests - Steve Freeman & Nat Pryce)
(1) Technique: Breaking out Splitting a Large Object into a Group of Collaborating Objects when: object is becoming complex why: object has multiple concerns (violates Single Responsibility) (2) Technique: Budding off Defining a New Service That an Object Needs and Adding a New Object to Provide It (A) Value Types: placeholder type introduce a placeholder type that - wraps a single field, or maybe - has no fields at all (B) Objects...
interface things fit together protocol things work together
(1) decompose our system value types objects decompose our system into value types and loosely coupled computational objects (2) building blocks lower-level objects into more capable objects use lower-level objects as the building blocks of more capable objects (src: Book_ Growing Object Oriented Software, Guided By Tests - Steve Freeman & Nat Pryce)