Eberhard Wolff, adesso AGTen Advices for Architects
About me• Eberhard Wolff• Architecture & Technology Manager at adesso• adesso is a leading IT consultancy in Germany• Speaker• Author (e.g. first German Spring book)• Blog: http://ewolff.com• Twitter: @ewolff• http://slideshare.com/ewolff• firstname.lastname@example.org
Why?• Educating architects internally at adesso• What should they know?• What is the bare minimum?
Software ArchitectSoftware architect is a general termwith many accepted definitionswhich refers to a broad range of roles. Not really well defined…
Software ArchitectureThe software architecture of a system is the set of structuresneeded to reason about it, which comprise software elements, relations among them, and properties of both.
Why We Care DefinesStructures PerformanceSoftware elementsnon-functionalRelationsProperties Availability Productivityrequirements & Software Architecture Maintainability quality Security Operations
Software Architect: Responsibilities• Manager• Responsibility: non-functional requirements / quality• Tool: Define and enforce architecture• Functional requirements covered by requirements process• Functional requirements influence the architecture
Agile Development i.e. ScrumWhere is Scrum Master Removes obstacles Enforces rules theArchitect Stories ? Product OwnerCreates stories Team Self-organizing Implements stories
You Are Not An Architect!• No manager• Need to convince not manage• Therefore: Not that different from a developer• More experienced• More knowledge
Is “Architect” a Good Metaphor?• Buildings are physical entities – Hard to change• Construction industry is established• …and has a long history• Buildings can be fully specified• Software can’t (see Agility)• Clear separation: Architect vs. construction worker• Common for a Software Architect to be a former developer• …or even doing some coding
Software Craftsmanship Manifesto (2009)• As aspiring Software Craftsmen we are raising the bar of professional software development by practicing it and helping others learn the craft. Through this work we have come to value:• Not only working software, – but also well-crafted software• Not only responding to change, – but also steadily adding value• Not only individuals and interactions, – but also a community of professionals• Not only customer collaboration, – but also productive partnerships
Architect as a Master Craftsman• More experienced• Knows the tools very well• Guides and helps others• Incorporates feedback• Improves the craft• Quality• Will work on code• But knows the bigger picture of the project• Education and work on the project at hand
Your Opinion Matters!• This applies to this conference• …and this talk• If it does not make sense to you – say so• Your opinion – your responsibility• Even if someone is a speaker – he might still be wrong• Never be intimidated!
Architecture = Trade Off• There are numerous ways to architect each system• There is no one single right architecture• Each architecture has strength and weaknesses• Think about architecture in terms of Trade Offs• Do they match your requirements?
Example for Trade Off: Persistence• Option: SQL – More control – Less infrastructure• Option: O/R mapper – Seemingly easier to use – But a complex piece of technology• Option: NoSQL – A lot of options with individual strength and weaknesses
Vocabulary• Approaches to architecting a system• Defines what kind of architectures and systems you can express• The more you know the better you can do trade offs• Will offer new perspectives on what you doing• Also it is interesting to learn what others do
How to Improve Your Vocabulary• Patterns – Fowler: Patterns of Enterprise Application Architecture – Gamma et al: Design Patterns – Buschmann et al: Patterns- Oriented Software Architecture – Hohpe: Pattern of Enterprise Integration• Evans: Domain Driven Design
How to Improve Your Vocabulary• Technologies – How many Persistence approaches do you know? – Should at least have a high level overview – There is life beyond standards – Can save a lot of time and effort• Conferences• Web Sites• Reviews
Again: Persistence• “Patterns of Enterprise Application Architecture” lists persistence approaches• Ruby on Rails uses Active Record (i.e. objects can store themselves)• myBATIS for easy persistence using SQL (Java / .NET)• …
Eat Your Own Dog Food!• Defining an architecture is easy• It is hard to create the right architecture• Need feedback• Eat your own dog food: Develop code yourself• Do pair programming• To become grounded
Broken Windows Theory• Once windows are not repaired…• …vandals will break more• …break into the building• …• Accepting compromises on quality is risky• …but if you strive for ultimate quality everywhere, you will fail• In particular with legacy software
Broken Windows in Architecture• Compromises on quality will become out of hand• Might speed up a project for a limited time• But: Will hurt productivity in the long run• …and ultimately slow it down• Higher quality can mean less cost and quicker delivery• Metaphor: Technical debt• Much like debt in real life
But…• There might still be broken windows• There might be more and less skilled developers• What do I do?
Domain Driven Design• “Tackling Complexity in the Heart of Software”• E.g. Ubiquitous Language for Code, Developers and Customers
Strategic Domain Driven Design• Bounded Context: Model used only in a specific part of the system• Context Map: Translate models from different parts of the system• Anti-Corruption Layer: Make sure the core domain is not corrupted
Strategic Domain Driven Design• Can be used to manage quality• What are the core business domains?• Focus on quality of those• Isolate them from the rest of the system• Let the best developer work on the most important parts
Strategic Domain Driven Design• Acknowledges that not all developers are equals• …and not all parts of a system will have the same quality• Allows you to steer which parts will be better
Measure and Reduce• No way to know all code by heart• Still: You and the team need to understand the state of the project• Need tools to measure and reduce information
Sonar• Server that integrates a lot of systems• Static code analysis (Findbugs, PMD etc)• Lines of Code, classes• Test code coverage• Complexity• Historized i.e. easy to spot trends• Easy to install• Visit http://nemo.sonarsource.org/ for examples
Draw Conclusions!• Do not try to enforce a certain value for a metric!• Metrics are used to reduce information and get warning signs• Use them to improve quality• If you enforce a value mindlessly problems will be avoided – not solved• …and measurements will become worthless
Dependency Management• Essential for measuring architecture• i.e. what is the structure in the code?• Why are Dependencies so important?
What is Architecture?• Architecture is the decomposition of systems in parts• No large or complex parts• No cyclic dependencies
Normal Dependencies• A and B might be packages or classes Component A• B depends on A, i.e. it uses classes, methods etc. Component B• Changes in A impact B• Changes in B do not impact A
Cyclic Dependency• B depends on A and A on B Component A• Changes in A impact B• Changes in B impact A• A and B can only be changed as one unit Component B• …even though they should be two separate units
Bigger cyclic dependencies Component A Component B Component C
Measure Dependencies!• …otherwise they will get out of hand• Cyclic dependencies mean: – It should be separated according to the architecture – …but it is not• JDepend – rather outdated• Structure 101• Sonargraph
Care about You are Not an Architecture is Code and Quality Architect Trade OffArchitecture Measure and Eat your own No Broken Vocabulary Reduce Dog Food Windows Dependencies People Want Strategic Matter To Improve Design And Remember: Your Opinion Matters!
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