TM354 Unit 1 - Approaches to Software Development

Question 1

What errors can arise in software with the characteristic = Malleability ?

Answer 1

As change is easy to make, changes may be be made without thorough consideration

Question 2

What errors can arise in software with the characteristic = Complexity ?

Answer 2

the more complex the software, the more chance there is of a change affecting other areas

Question 3

What errors can arise in software with the characteristic = Size?

Answer 3

The greater the number of lines of code, the greater the number of likely errors

Question 4

What is the defining quality of good software system?

Answer 4

Useful, Usable, Reliable, Flexible, Available, Affordable

Question 5

How does greater flexibility make software system more affordable

Answer 5

Users needs change over time. Time to implement change in flexible system is less than for less flexible system. As labour costs are highest component of software cost, flexible s/w is more affordable

Question 6

Give 2 reasons why software might not meet users needs

Answer 6

software is usually outofdate when delivered because:

1. some needs are missed during requirements capture
2. users’ needs change with time

Question 7

suggest a means of measuring maintainability of s/w system

Answer 7

1. effort to locate and fix errors

2. effort to adapt s/w to meet users’ needs

Question 8

what can be learnt from legacy systems about developing good system

Answer 8

Legacy sys may start with flexibility, but change over time This needs standards and documentation.

Question 9

suggest a reason why legacy systems will always be a problem

Answer 9

inherent malleability makes s/w easy to change. Metalworking analogy. Blacksmith - component brittle

Question 10

why consider splitting large project into chunks

Answer 10

limit to how much one person can remember at any time. easier to manage tasks if split into chunks

Question 11

how does complexity of s/w affect maintenance

Answer 11

it is essential to make change without knowing all about the system. change is difficult when there are many dependencies

Question 12

what is a module

Answer 12

module is an identifiable part. that is considered separately

Question 13

why does it help to have low coupling

Answer 13

few dependencies. therefore any errors are less likely to propagate through system

Question 14

give examples of kinds of info that would be valuable when considering a change

Answer 14

2 kinds of info :
which modules are clients of the module in question
what assumptions were made  in client modules of module in questions

Question 15

what are context dependencies

Answer 15

services of other modules that module needs to work properly

Question 16

what are benefits of modules with defined interfaces

Answer 16

developers need to know only about the module
developers can understand aspects of software more thoroughly
should be easier to find bugs
chance of module reuse increased

Question 17

why does it help to have high cohesion

Answer 17

module carries out sensible set of operations or activities.
it implies one major abstraction per module. easier to understand the purpose of module

Question 18

what characteristics should a module display to show it is easy and cheap to develop and maintain

Answer 18

module should have low coupling and high cohesion and well defined interface

Question 19

why is it important to achieve balance between coupling and cohesion

Answer 19

may have choice between small set of loosely coupled less cohesive modules or larger set of tightly coupled more cohesive modules.former is difficult to understand. In latter, relationships may be over complex

Question 20

suggest similarities and differences between software architecture and building architecture

Answer 20

they are both abstractions of the structure of a system. they represent systems that affect concerns of different stakeholders.
Changing a building once complete is expensive. changing details or internal decoration is cheap.
Software different , particularly malleability and complexity

Question 21

what are characteristics of a component

Answer 21

component is module with good abstraction for a problem.
component should be capable of being reused or being replaced later within existing software. well defined interface with strong cohesion and low coupling

Question 22

how does concept of an architecture contribute to component reuse

Answer 22

arch of s/w sys embodies high level decisions about structure of system and this architec may apply to more than one system

Question 23

which form of decomposition might be used in s/w architecture

Answer 23

basic form of decomposition used in s/w arch is partitioning to meet separate concerns, each being addressed by subsystem. e.g separate UI from core business, or build / reuse components for some of the partitions

Question 24

what are similarities and differences between components and services

Answer 24

both promote reuse and flexibility.
both use public interfaces to allow requestors to make use of functionality without relying on their implementation
component usually implemented in an oo technology
service uses communication standards that allow interoperation of diverse technologies

Question 25

give characteristics of an engineering approach that support argument that s/w development is an engineering discipline

Answer 25

meeting set of requirements
defined process and clear activities
developers can apply skills
validation and verification needed
use of tools and standards
follows code of practice

Question 26

what is a development process

Answer 26

set of rules that defines how a sw dev project should be carried out. no of activities and process model indicates how these are ordered

Question 27

difference between customer and user ?

Answer 27

customer is person who pays. Users is person who uses.

Question 28

why is maintenance a core activity ?

Answer 28

Maint allows a system to evolve over its lifetime so it continues to be useful

Question 29

what task is needed when s/w dev is partitioned into number of increments

Answer 29

task devoted to the integration of the increments will be needed

Question 30

what are assumptions of the waterfall model

Answer 30

assumption that one activity or phase is finished, it is not revisited.no need for rework. all assumes and endpoint is identified.

Question 31

why might a s/w dev company specialise in specific sector e.g. banking, health

Answer 31

through specialisation, company can foster experience in given domain. Developers would have knowledge to understand the problems raised by the users.

Question 32

what is added to a Dev process with introduction of Risk Mgt ?

Answer 32

identification, evaluation, reviewing of risks

steps introduce feedback into process - risks are controlled

Question 33

why is traceability important

Answer 33

important for reconstruction of significant events

should be able to trace backwards from a component

Question 34

how does doco contribute to traceability

Answer 34

doco records the progress from req to implem. u can trace from requirement to implementation

Question 35

what s/w system would you minimize or avoid doco

Answer 35

if s/w has short lifespan or will be discarded

Question 36

how would you characterise agile doco?

Answer 36

agile doc should be gathered with a purpose.

should be easy to use and justify the effort

Question 37

why is it important to review notebook

Answer 37

to identify what worked and what did not. helps to trace events leading to decisions made.

Question 38

What is a model?

Answer 38

An abstract representation of a specification, system or point of view

Question 39

What is a good model ?

Answer 39

A ‘good model’ is an abstraction that allows those involved to concentrate on the essentials of a complex problem by excluding non-essential details while capturing those of interest.

Question 40

What are 2 kinds of rule that govern the use of a modelling language?

Answer 40

A modelling language is normally diagrammatic, although it can be textual. In common with natural language, there are two distinct
kinds of rule:
◦ those that determine whether or not a diagram is legal – the syntax of a diagram
◦ those that define what a legal diagram means – the semantics of a diagram.

Question 41

Does a modelling language need to be associated with a particular development process?

Answer 41

No, a modelling language does not dictate how it should be used and it is up to a development process to define which notations are appropriate and how they should be used. With experience practitioners tend to pick and mix from different modelling languages and use the notations that are most appropriate to the task – most modelling languages do not provide notations for all types of tasks.

Question 42

What are the required characteristics of a std modelling language?

Answer 42

No, a modelling language does not dictate how it should be used and it is up to a development process to define which notations are appropriate and how they should be used. With experience practitioners tend to pick and mix from different modelling languages and use the notations that are most appropriate to the task – most modelling languages do not provide notations for all types of tasks.

Question 43

How does a standard modelling language contribute to software development?

Answer 43

When choosing a modelling language, it should be:
◦ sufficiently expressive
◦ easy to learn and use
◦ unambiguous
◦ widely used
◦ supported by suitable tools.