Chapter 7 - Modifiability

Question 1

definition of modifiability

Answer 1

pertains to the cost and risks of making changes

Question 2

3 issues with regards to modifiability

Answer 2

• what can change?
• what is the likelihood of change?
• when is the change made and who makes it?

Question 3

In general scenario, 3 possible values for “Source”

Answer 3

end user

developer

system administrator

Question 4

In general scenario, 2 possible values for “Stimulus”

Answer 4

directive to:

• add/delete/modify functionality
• change quality attribute, capacity, or technology

Question 5

In general scenario, 6 possible values for “Artifact”

Answer 5

code
data
interfaces
components
resources
configurations

Question 6

In general scenario, 3 possible values for “Response”

Answer 6

• make modification
• test modification
• deploy modification

Question 7

In general scenario, 5 possible values for “Environment”

Answer 7

• runtime
• compile time
• build time
• initiation time
• design time

Question 8

In general scenario, 6 possible values for “Response Measure”

Answer 8

• number, size, complexity of artifacts affected
• effort
• calendar time
• money
• extent to which modifications affect functions or quality attributes
• new defects introduced

Question 9

2 Primary goal of modifiability tactics

Answer 9

• control the complexity of making changes

- control the time and costs to make changes

Question 10

4 categories of modifiability tactics

Answer 10

• reduce the size of a module
• increase cohesion
• reduce coupling
• defer binding

Question 11

1 tactics for reducing the size of a module

Answer 11

split module

Question 12

what does it mean to split a module?

Answer 12

refining modules with a great deal of capability into several smaller modules to reduce the average cost of future changes

Question 13

1 tactic increasing cohesion

Answer 13

increase semantic coherence

Question 14

what does it mean to increase semantic coherence

Answer 14

and two program units A and B whose responsibilities do not serve the same purpose should be placed in separate modules

Question 15

5 tactics for reducing coupling

Answer 15

• encapsulate
• use an intermediary
• restrict dependencies
• refactor
• abstract common services

Question 16

what does it mean to encapsulate

Answer 16

to introduce an explicit interface to a module including an API and associated responsibilities

Question 17

what does it mean to use an intermediary

Answer 17

using some intermediate responsibility to break a dependency between to responsibilities A and B

Question 18

what does it mean to restrict dependencies

Answer 18

restrict modules which a given module interacts with or depends on

Question 19

what does it mean to refactor

Answer 19

undertaken when tow modules are affected by the same change because they are at least partial duplicates

Question 20

what does it mean to abstract common services

Answer 20

implement a single service used slightly differently by two different modules one time in a more general and abstract form

Question 21

what does it mean to defer binding

Answer 21

the later in the life cycle in which things are bound typically leads to greater flexibility (in terms of modifiability)

Question 22

the importance of allocation of responsibilities with regards to modifiability

Answer 22

determine which changes or categories of changes are likely to occur through consideration of changes in technical, legal, social, business and customer forces

Question 23

3 important tasks pertaining to allocation of responsibilities with regard to modifiability for each potential change or category of changes

Answer 23

• determine the responsibilities that need to be added to make the change
• determine what other responsibilities are impacted by the change
• allocate responsibilities in such a way so that groups of responsibilities affected by a change are in the same module (maximize local changes!)

Question 24

3 issues with the coordination model in regards to modifiability

Answer 24

• determine which functionality or quality attribute can change at runtime and how this affects coordination
• determine which devices, protocols, and communication paths used for coordination are likely to change
• use a coordination model to reduce coupling for elements that are likely to change

Question 25

3 issues with the data model in regards to modifiability

Answer 25

• determine which changes to the data abstractions, their operations, or their properties are likely to occur
• for each category of change, determine who will make the changes and ensure that they have the correct privileges
• design the data model so that allocated items change together

Question 26

In regards to the data model, 4 things to consider for each potential change or category of change

Answer 26

• determine which data abstractions need to be added, changed, or deleted
• determine whether there would be any changes to creation, initialization, manipulation, translation, or destructions of these data abstractions
• determine which other data abstractions are impacted by the change
• ensure the allocation of data abstractions minimizes the number and severity of modifications

Question 27

3 issues with the mapping among architectural elements in regards to modifiability

Answer 27

• determine if changing the way which functionality is mapped is desirable
• determine the extent of modifications necessary to accommodate changes to functionality or quality attributes
• ensure that changes are performed with mechanisms that utilize deferred binding of mapping decisions

Question 28

3 issues with resource management in regards to modifiability

Answer 28

• determine how changing a responsibility or quality attribute will affect resource usage
• ensure that resources after the modification are sufficient to meet system requirements
• encapsulate all resource managers and the policies they implement and bindings are deferred as much as possible

Question 29

4 things to consider for each type of change with regards to binding time

Answer 29

• determine the latest time a given change will need to be made
• chose a defer-binding mechanism
• determine the cost of introducing and making changes using the chosen mechanism
• do not introduce so many binding choices so as to impede change

Question 30

2 issues with the choice of technology in regards to modifiability

Answer 30

• determine which modifications are made easier or harder by the choice of technology
• chose technologies that will support the most likely modifications