layering your apps
Increasing Signal by Removing Noise
- DDD Consultant/Trainer
- Architect
- Legacy Cartographer
- PHP Dublin Organiser
- DDD IE Organiser
@barryosull
Barry O Sullivan
About me
Hands on Session
- Map our inputs and outputs
- Map our libraries/services
- Discuss where concepts should belong
What we'd like to do
applying ddd
What usually happens
applying ddd
What gets in the way
applying ddd
Increase signal
BY REMOVING NOISE
Noise type 1
input & output
Input & output
What goes in and what goes out
ports & adapters
Driver
Adapters
Driven
Adapters
Hide details behind interfaces
Mapping your
inputs & outputs
- 15 minute session
- List all the inputs and outputs of your system
- HTTP
- Database
- Messaging
- etc. . .
Noise type 2
translation between DSLs
Domain specfic languages (DSL)
"A domain-specific language (DSL) is a computer language specialised to a particular application domain."
Two types: External and Internal
Libraries are Internal DSLS
translation
Domain and Library code must translate
translation
Mapping your
libraries/Services
- 20 minute session
- List all the libraries/services you use
- DBAL lib
- Template engine
- Datetime lib
- etc . . .
- Where do they live currently?
Layering your app
Where should concepts belong
onion architecture
Core
Domain
Application
Infrastructure
- Domain details at centre
- Implementation details at edge
- Application coordinates
- Dependencies point inward
HTTP
Adapter
Application
Repositories
External Services
Domain
Core
onion architecture
Where do concepts belong
- 20 minute session
- Takes the results of the last 2 sessions
- Ask where they should belong?
- Input/Output?
- Translation?
- Is it actually infra/app/domain/core?
- What would make your jobs easier?
next steps
We've removed a lot of noise;
now we focus on the signal.
- Iterate on the language expressed by the interfaces
- Do this with domain experts
- Language should be domain focussed if possible
- Iterate on domain concepts free from the noise
- Concepts should begin to emerge naturally
conclusion
- Sometimes it's hard to see the forest for the trees
- Discover the domain by removing unnecessary implementation details
- Develop a language that allows communication and collaboration
Domain