software architecture + architectural styles

Question 1

architecture

Answer 1

set of structures needed to reason about the system

Question 2

in which four ways can we describe architecture

Answer 2

formal notations; mathematical
architecture description languages; e.g. backus naur form
box and line
ball and socket; semiformal development of box and line

Question 3

what are the 3 steps in architectural design

Answer 3

structuring the system into key components and the communication between them
control modelling to organise the system
modular decomposition of sub systems

Question 4

what are the 4 steps we take to identify sub systems and their interfaces

Answer 4

identify major functions the system should provide
group together similar functions to get bigger sub systems
can decompose these further
specify interfaces

Question 5

what should subsystem and component interface descriptions include

Answer 5

a name
operations within it
exception handlers
non-functional properties

Question 6

ball in ball and socket

Answer 6

provided
provides a service
does the processing

Question 7

socket in ball and socket

Answer 7

required
service user/caller

Question 8

control model

Answer 8

controls the flow between subsystems

Question 9

what are the two types of control models

Answer 9

centralised control and event based systems

Question 9

centralised control

Answer 9

one subsystem has overall responsibility for control

Question 9

what are the two types of centralised control

Answer 9

call return model
manager model

Question 9

manager model

Answer 9

for concurrent systems
the controller controls the stopping and starting and coordination of all system processes

Question 9

event based systems

Answer 9

each subsystem can respond to externally generated events from other subsystems or the systems environment

Question 10

call return model

Answer 10

for sequential systems
hierarchical; main() starts the entire system and control is passed down the hierarchy

Question 10

what does architectural choice usually affect

Answer 10

non functional requirements

Question 11

what are the 6 architectural concepts that we could trade-off on

Answer 11

performance
security
safety
availability
maintainability

Question 12

performance

Answer 12

localise critical operations and minimise communications
larger components

Question 13

security

Answer 13

layered architecture with critical assets in the inner layers
don’t want functionality close to communication or the ui as this makes the system easier to hack

Question 14

safety

Answer 14

localise safety critical features in a small number of subsystems
keeping it localised makes it harder to hack

Question 15

availability

Answer 15

redundant mechanisms and components for fault tolerance so if a component crashes its copy can be used

Question 16

maintainability

Answer 16

fine grain replaceable components which are easy to understand and not highly coupled

Question 17

architectural styles

Answer 17

specific templates which are general and reusable

Question 18

what are 5 common architectural styles

Answer 18

input-output-process
plug in
layered
repository
client server

Question 19

input-output-process

Answer 19

monolithic systems
business logic is decoupled from the ui

Question 20

what are two benefits of input-output-process

Answer 20

if the ui changes or breaks it doesn't affect the logic logic can be tested quickly and independently without the need for a ui

Question 21

plug in

Answer 21

component that provides a service within the overall system and depends on it it has to conform to the systems plug in contract

Question 22

what is a positive of plug in

Answer 22

the system is extensible and modular

Question 23

what are two negatives of plug in

Answer 23

changes in the system can break the plug in can be compromised if not managed properly

Question 24

layered

Answer 24

components are organised into subsystems and each one can only communicate with the one below it

Question 25

what are two benefits of layered

Answer 25

architecture is changeable and portable as long as interfaces stay unchanged each layer can be developed by different teams independantly

Question 26

what is a good use of layered

Answer 26

authentication and authorization

Question 27

repository

Answer 27

data generated in one component is used in other components

Question 28

what is repository used in

Answer 28

command and control systems management information systems

Question 29

what are two positives of repository

Answer 29

good for sharing large amounts of data components can be independent

Question 30

what are three negatives of repository

Answer 30

distributing components over multiple systems is difficult integrating new components may be tricky as they have to comply with the agreed repository schema single point of failure

Question 31

client server

Answer 31

servers offer services to clients usually connecting via internet protocols

Question 32

two positives of client server

Answer 32

servers can be distributes across a network general functionality doesn't need to be implemented by all servers

Question 33

a negative of client server

Answer 33

each server is a single point of failure and susceptible to denial of service attacks