Week 8

Question 1

What are the views in 4+1 architectural view models, and what diagrams are used to represent them?

Answer 1

Logical view - functionality the system provides to users - class & sequence diagrams

Development view - illustrates system from the programmers perspective - component and package diagrams

Process view - dynamic aspects of the system, runtime behaviour etc - activity diagram

Physical view - illustrates the system engineers view - deployment diagram

Scenarios - small set of use cases or scenarios, describing sequences of interactions between objects and processes

Question 2

What is system architecture?

Answer 2

Fundamental organisation of a system - components, their relationships, the environment etc.

Question 3

What is an architectural description?

Answer 3

A set of products that document the architecture

Question 4

What is an architectural view?

Answer 4

Representation of a particular system or part of a system from a particular perspective

Question 5

What is an architectural viewpoint?

Answer 5

Template that describes how to create and use an architectural view

Includes name, stakeholders, concerns addressed by the viewpoint

Question 6

What does an architectural style describe?

Answer 6

Types of components

Types of connectors

Topology (constraints on possible compositions)

Question 7

What are the 4 steps in the processing model of a client-server communication?

Answer 7

Client initiates request

Request passes through network

Server responds

Response returned via network

Question 8

What properties does client-server communication have?

Answer 8

Transparency - server can be on different machines without affecting the client, client knows the server but not the other way round

Heterogeneity - different machines, operating systems

Redundancy

Question 9

What are the 4 major forms of redundancy?

Answer 9

Hardware redundancy

Information redundancy (e.g error detection & correction)

Time redundancy

Software redundancy

Question 10

In MVC, what is the model?

Answer 10

Provides the functionality of the program

Question 11

In MVC, what is the view?

Answer 11

Presents the data from the model to the user, updating when data has changed

Question 12

In MVC, what is the controller?

Answer 12

Accepts user input in the form of events. Created by the view

Question 13

In MVC, what is a propagation mechanism?

Answer 13

Enables the model to inform the view that the data has changed

Question 14

What two approaches are there for dividing a software system into subsystems?

Answer 14

Layering - levels of abstraction

Partitioning - each subsystem focuses on different aspect

Question 15

In a layered architecture, what is the difference between closed and open architecture?

Answer 15

Closed - messages can only be sent to the next lowest layer

Open - messages can be sent to any lower layer

Question 16

In P2P networks, how can peers be found (3 ways)?

Answer 16

Directory service - central server or “rendezvous peer” gives listing of clients

Multicast - peers announce their presence on a communication channel

Neighbour model - peers talk directly to each other

Question 17

What are 4 advantages of P2P networks?

Answer 17

Very flexible

Evolves with minimal effort

Efficient

Heterogenous

Question 18

What are 3 disadvantages of P2P networks

Answer 18

Security - almost impossible to authentiate

Duplication

Data corruption (??? wtf idk)

Question 19

What is the difference between error, fault and failure?

Answer 19

Error - a human mistake in software development

Fault - the result of errors

Failure - dynamic manifestation of faults

Question 20

What is static validation (3 examples)?

Answer 20

Validation carried out without executing the program

e.g. software inspection, formal verification, static typing

Question 21

What is dynamic validation (2 examples)?

Answer 21

Validation carried out by executing the program

e.g. testing, defensive programming

Question 22

2 pros, 3 cons of static validation

Answer 22

+ detection is earlier in the process - need not be complete

+ Correction is easier and cheaper

• Reduced flexibility
• increased bookkeeping
• incomplete

Question 23

What sort of things does code inspection detect?

Answer 23

Stuff like resharper. Unreachable code, unitialised variables, array bounds, infinite loops

Question 24

Which conversions between subtype and supertype are permissible with automatic coercion?

Answer 24

subtype to super type

Question 25

What is the difference between weak typing and strong typing?

Answer 25

Weak: Supporting implicit typing, overloading or both

Strong: coercions only allowed if value is preserved, otherwise cast needed

Question 26

What is the difference between static and dynamic typing?

Answer 26

Static typing: done by compiler, every name needs type declaration

Dynamic typing: done at runtime, requires dynamic binding between object and type