2 Software Architecture Basics

Question 1

Design mode

Answer 1

• contains several diagram types, incl. interaction, package and class diagrams
• conecptual classes are needed
• -design classes show definitions of software artifacts
• -design model describes static and dynamic facets

Question 2

architectural design

Answer 2

early stage of system design process

link beetween analysis and design

Question 3

Divide & conquer

Answer 3

complex systems need to be partitioned
variety of terms:
-packages
-components
-subsystems
-layers
-tiers

Question 4

Cohesion & couplin

Answer 4

cohesion: zugriffe innerhalb einer partition
coupling: zugriffe zwischen partitionen

good architecture -> high cohesion, low coupling

Question 5

Architectural views

Answer 5

Functional/logical view
Code/module view
Development/structural view
Concurrency/process/thread view
Physical/deployment view
User action/feedback view
Data view

Question 6

What constitues a software architecture

Answer 6

Logical view: organization of the software classes into software elements (packages etc); describes logical partitioning of the system into partitions and relationsships among htem

Deployment architecture view: distribution of software elements on computational resources and coomu. among them

Question 7

Typical system layers

Answer 7

UserInterface /Presentation Layer
Application logic and domain layer
technical services layer

Question 8

Distributed Systems

Answer 8

Architectural models:

• client-server architectures
• multi-tier architectures
• distributed object architectures

Question 9

Pros of distrib.sys

Answer 9

Pro:

• resource sharing
• openness
• concurrency
• scalability
• fault tolerance
• transparency

Question 10

Cons of distrib.sys

Answer 10

• complexity
• security
• manageability
• unpredicatbiliy
• testability

Question 11

Client-Server architecture

Answer 11

set of standalone servers that provide specific services
set of clients who call those servers
network that allows access

Question 12

Thin client deployment model

Answer 12

• application processing and data management is carried out by the server, client just resp. for data presentation/UI
• often used when legacy systems are migrated to client-server architectures
• places heavy processing load on the server and network

Question 13

Fat client deployment model

Answer 13

the server just manages the data

client software implements application logic and presentation/UI

Question 14

3-Tier deployment architecture

Answer 14

each architectural tier executes on seperate machine
tiers = physical nodes
client server (appl. process.) server (data)
better scalability

Question 15

Architectural styles

Answer 15

set of architectural constraints
that restrict the roles/features of architectural elements
and the allowed relationships among those elements

Question 16

Architectural styles categories

Answer 16

• Structure: Object oriented, layered arch., component-based arch.
• Deployment: N-Tier, 3-Tier
• Communication: Service-Oriented Arch. (SOA), Message Bus

Question 17

Reference Architecture

Answer 17

generic model
acts as a standard on which systems can be built
ref. arch. models can be used as templates
^ are more concrete

Question 18

UI Layer

Answer 18

presentation of the data
managing the interaction with the user
should not process anything, forward it to appli. layer

Question 19

Application Layer

Answer 19

handles incoming requests
remember session state and flow of work
rule of thumb: one controller/facade per use case

Question 20

Domain Layer

Answer 20

contains the domain objects and application logic

very application specific

Question 21

Facades

Answer 21

• reduce coupling -> facade classes are used
• serves as entry point to a set of related software classes
• servers as the interface to the respective software element
• black-box/information hiding principle

Question 22

Component-Based architecture

Answer 22

compose software sys. from reusable components
a component is a unit of composition
can be deployed independently
typically feature-oriented

Question 23

Architectural patterns

Answer 23

codification of prev. discussed archtiectural aspects

pattern -> crosses the boundaries of architectural elements

Question 24

Software Patterns

Answer 24

patterns are recurring solutions for recurring problems

architec. pat. are software patterns

Question 25

Terminology - Architectural Style

Answer 25

cross cutting principles (object oriented style, modular style, etc.) independent of application domain

Question 26

Terminology - Reference Architecture

Answer 26

defines domain concepts, components and subsystems that can be used as a template

Question 27

Terminology - Architectural Pattern

Answer 27

solution to recurring situation where several forces have to be balanced

Question 28

Model-View Seperation Principle

Answer 28

different concerns
allows to create several UIs
testing UI is hard, allows to test appli seperatly

appl logic + UI = Smart UI Anti Pattern

Question 29

Model View Controller MVC Pattern

Answer 29

Model: containts core funcitonality and data
Views: display information to user
Controllers: handle user input

Views + Controllers = UI

Question 30

Advantages of an Explicit Architecture

Answer 30

Stakeholder communication
system analysis
large-scale reuse
project planning