Chapter 2.1 - Software Architecture Flashcards
What is Software Architecture?
Set of structures which comprise software elements, relations between them and their properties
What is a purpose of software architecture?
- Efficiency of the dev process
- Minimalization of Risk
- Mitigation of misunderstandings
- Planing of evolution, reuse
What is System?
collection of components,
their boundaries, static structure and behavior
What is enviroment?
Everything that influences upon system. Politics, Operations, Development
Who is a Stakeholder?
A Person or entity with interests or concerns about system.
Two most important Stakeholders are principal and the architect
What is a View?
A representation of a system from a specific perspective.
To address the concerns of stakeholders.
Focused on a particular system aspect.
E.g Logical view, Deployment view, Process view.
What is a Viewpoint?
A guideline or template for creating views.
To define the rules for building consistent views.
Defines methods for describing system aspects.
E.g Logical viewpoint, Physical viewpoint, Behavioral viewpoint.
What is a system Model?
Abstraction of the system.
There are different kinds:
Object -> structure of system
Functional -> functions of system
Dynamic -> event flow of system
data -> storage system
What is 4+1 view model?
Model that describes software arch using 5 view points
1. Logical (end user / designer view)
2. Process (Performance, Scalability)
3. Implementation
4. Deployment
5. Use cases
What comprises Logical view?
Structure and functionality of the system.
Key components, classes, and their relationships.
- Class diagram (for o.o)
- Object diagram
- State diagram
- Composite structure diagrams
What comprises Implementation View?
Code structure and organization.
Module decomposition, libraries, and frameworks.
1. Package diagrams (showing modules and dependencies).
2. Folder structure (for organizing the codebase).
What comprises Deployment / Physical
View?
Hardware and network topology.
Mapping of software components to physical infrastructure.
1. Deployment diagrams (showing servers, networks, and devices).
2. Infrastructure diagrams (detailing cloud-based or on-premise setups).
What comprises Process View?
System behavior at runtime.
Concurrency, synchronization, performance, and scalability.
From Scenario we create:
1. Sequence diagrams (showing interactions between components).
2. Activity diagrams (modeling workflows and concurrent execution).
3. Thread/process models (explaining parallelism and synchronization).
Which viewpoint can u ignore with a single process app?
process viewpoint
Which viewpoint can u ignore with a small app?
implementation viewpoint
What 3 attribute have Models?
- Reduction -> irrelevant stuff can be omitted
- Pragmatism -> they serve a purpose never good for everything
- Mapping -> They always map to something (copies of originals)
What is a Difference between As-Is and To-Be Model
As-Is Model: Customers must visit a bank branch to open an account, sign paperwork, and wait for manual processing.
To-Be Model: Customers can apply online, upload documents digitally, and get instant approval using automation.
What are the 7 steps of modeling
- Understand
- Cenceptualize
- Abstract
- Define
- Construct
- Evaluate
- Refine
What Methods are there to deal with Design Trade-offs?
ATAM - Architecture Trade-off Analysis Method
MCDM - Multi-criteria decision-making methods
How does the ATAM Quality Attribute Utility Tree works?
At the top we have the Utility
second level: Performance, Availability, Security, Usability etc.
third level Scenarios
Then the scenarios need to prioritized (L/M/H)
Focus on the prioritized elements from each branch
What is Partitioning / Decomposition?
top-bottom Dividing system into subsystems to achieve high cohesion and low coupling.
What is clustering?
bottom-up way to group similar objects as clusters.
What is modularity?
decomposition of system
What’s the goal of Modularity
Information hiding,
easier maintenance
reusability
work distribution
…
Issues of functional decomposition?
Functionality spread all over system
High complexity of the code and system
What is modular decomposition?
system decomposition into modules
What is a black-box model?
Black-box model presents the funcitonality of the system
What is white-box model?
White box shows how the system works internally
What is component-connector model?
Component that is assigned a connector to help regulate interactions.
e.g File transfer, Stream, Shared DB, Message Bus
How does the Decomposition work?
“divide and conquer”
1. Try to isolate smaller manageable parts
2. build interfaces between them
What is coupling?
Average degree of interdependency between modules.
What is Cohesion?
The dual of coupling. How related are the modules in component.
What is a software component?
It’s not just a class or file it’s more abstract than that.
- independent executable entity
- consisting of an interface that handles all outside connections
What are 5 characteristics of a software component?
Standardized,
Independent,
Composable,
Deployable,
Documented,
hint: similar to micro-service, but differs. e.g interfaces instead of REST requests etc
Name 3 basic elements of a component Model
- Interfaces (Composition, definition, etc)
- Usage information (Naming Convention, Meta-data),
- Deployment and use (Documentation, Packaging)
What’s the purpose of interface in component model
Specification of the Language e.g java Interface can implement different kinds of service. (PaymentProcessor - Paypal / Card / etc)
It defines the component for frameworks like WSDL / EJB or Swagger (allows for easier understandability of service)
What’s the purpose of Usage in component model
Naming convention - e.g for URL
Meta-data - info to users what services are provided
What’s the purpose of Deployment in component model
Packaging - how should components be packaged, as they are supposed to be independent
What are 3 types of component composition?
- Sequential - There is a glue in the middle
- Hierachical - A uses interface of B
- Adaptive - A & B are parallelly used
Was ist eine Dependency Structure Matrix (DSM)?
Eine DSM ist eine Matrixdarstellung von Abhängigkeiten zwischen Elementen in einer Softwarearchitektur. Sie hilft, komplexe Strukturen zu analysieren und zu optimieren.
Welche Vorteile bietet die Dependency Structure Matrix?
✅ Skalierbare Darstellung komplexer Abhängigkeiten
✅ Erkennung von Mustern und Anti-Patterns
✅ Automatische Architektur-Analyse durch Partitionierung
✅ Effiziente Zyklus-Erkennung
Welche Herausforderungen gibt es bei der Nutzung von DSM?
⚠️ Qualität der DSM hängt von der Genauigkeit der Daten ab
⚠️ Versteckte Abhängigkeiten können unerwartet auftauchen
⚠️ Weniger intuitiv als Graph-Darstellungen
Welche Prinzipien sind für modularen Software-Entwurf wichtig?
✅ Geringe Kopplung: Minimiert Abhängigkeiten zwischen Modulen
✅ Hohe Kohäsion: Module sollten zusammenhängende Funktionen enthalten
✅ Einzelverantwortungsprinzip (SRP): Ein Modul sollte nur eine Aufgabe haben
Was bedeutet „Separation of Concerns“ in der Softwarearchitektur?
Das Prinzip trennt verschiedene Verantwortlichkeiten in unterschiedliche Module, um Verständlichkeit, Wartbarkeit und Wiederverwendbarkeit zu verbessern.
Was besagt das Liskov-Substitutionsprinzip?
Eine Unterklasse muss sich nahtlos anstelle ihrer Basisklasse verwenden lassen, ohne das Verhalten zu ändern.
What does the Interface-segregation principle(ISP) say?
An interface should have only the necessary methods that a specific class needs. If an interface is too large (fat interface), it should be split into smaller, more specific interfaces to avoid unnecessary dependencies.
Warum ist Code-Duplikation problematisch?
🔴 Erhöht den Wartungsaufwand
🔴 Kann zu Inkonsistenzen führen
🔴 Erschwert Änderungen im Code
Wie beeinflusst Architektur die externe Softwarequalität?
✅ Sicherheit: Viele Schichten können Angriffsflächen vergrößern
✅ Performance: Zu viele Indirektionen können die Leistung beeinträchtigen
✅ Wartbarkeit: Gute Modularität verbessert Änderbarkeit und Fehlerbehebung
Was sind Vorteile und Herausforderungen beim Code-Reuse?
✅ Vorteile: Zeitersparnis, Kostenreduktion, höhere Qualität
⚠️ Herausforderungen: Unterschiedliche Anforderungen, Wartungsaufwand, Lizenzprobleme
Wie beeinflusst Architektur die Testbarkeit?
✅ Hohe Modularität verbessert Unit-Tests
✅ Geringe Kopplung erleichtert Testisolierung
❌ Viele Abhängigkeiten erschweren das Testen
❌ Monolithische Systeme sind schwer zu testen
Wie beeinflusst Architektur die Sicherheit?
🔐 Schichten-Architektur: Reduziert Angriffsfläche
🔐 Demilitarized Zone (DMZ): Trennung zwischen internen und externen Netzwerken
⚠️ Zu viele Abstraktionsschichten: Erhöhen potenzielle Schwachstellen
Was besagt das Open-Closed-Prinzip?
Softwaremodule sollten erweiterbar, aber nicht veränderbar sein. Das bedeutet, dass neue Funktionen hinzugefügt werden können, ohne bestehende zu ändern.
Warum ist das Liskov-Substitutionsprinzip wichtig?
Ermöglicht, dass Subklassen anstelle ihrer Basisklassen verwendet werden können, ohne dass das Verhalten unerwartet verändert wird.
“If it looks like a duck, quacks like a duck but needs batteries to run then it’s probably not a duck.”
Wie funktioniert eine DMZ in der Softwarearchitektur?
DMZ is not as hostile as the internet
▪ DMZ and internal network are two separate networks. Compromising a machine in the DMZ is not the same as compromising the internal network
▪ Place public servers in the DMZ and place internal machines in the internal network: compromising them requires two steps
Was ist „Design by Contract“ (DbC)?
DbC ist ein Konzept zur Entwicklung robuster Software, bei dem Verträge zwischen Komponenten spezifiziert werden. Diese enthalten:
✔ Preconditions: Bedingungen, die erfüllt sein müssen, bevor eine Methode aufgerufen wird
✔ Postconditions: Bedingungen, die nach der Ausführung erfüllt sein müssen
✔ Invarianten: Bedingungen, die während der gesamten Laufzeit einer Komponente bestehen müssen
What is a Single responsibility principle?
A class should only have one reason to change
If there are two reasons for a class to change, we have to split the functionality into two classes.
▪ Each class will handle only one responsibility
▪ If we need to make a change, we should make it in the class that handles it
▪ This leads to cohesion at the package/implementation level
How does a 3-tiered Architecture looks like?
Internet -> Load Balancer -> Webservers -> Dataserver
Webserver is the App at the same time
How does a 4-tiered Architecture looks like?
Internet -> Load Balancer -> Webservers -> Appservers -> Dataserver
