Chapter 2 - Why is Architecture Important

Question 1

10 reasons an architecture is vital

Answer 1

• will inhibit or enable a system’s driving quality attributes
• allows you to reason about and manage change as the system evolves
• enables early prediction (i.e. before system is built) about a system’s qualities
• when well-documented it enhances communication among stakeholders
• defines a set of constraints on subsequent implementation
• dictates the structure of an organization and vice versa
• allows the architect and project manager to reason (which decent accuracy) about the cost and schedule
• can be created as a transferable, reusable model that can form the heart of a product line
• guides design by restricting design alternatives (hence reducing the design complexity)
• can be the basis for training a new team member

Question 2

3 additional aspects that are further enabled by an architecture but do not necessarily depend on it

Answer 2

• clearly documents early (and hence expensive to change) design decisions (can include the rationale behind and thus make easier to understand later)
• can be a basis for evolutionary prototyping
• allows a better understanding of the COTS or open source SW that will be needed later and facilitates its inclusion

Question 3

How is arch involved with system performance

Answer 3

involves managing the time-based behavior of elements, their use of shared resources, and the frequency and volume of inter-element communication

Question 4

How is arch involved with system modifiability

Answer 4

involves assigning responsibilities to elements so that the majority of changes to the system will affect a small number of those elements

Question 5

How is arch involved with system security

Answer 5

involves managing and protecting inter-element communication and controlling which elements are allowed to access which information

Question 6

How is arch involved with system scalability

Answer 6

involves localizing the use of resources to facilitate introduction of higher capacity replacements

Question 7

How is arch involved with system reusability

Answer 7

involves restricting inter-element coupling so that a given element has minimal attachments to its environment when extracted

Question 8

Why is it important that an architecture facilitates managing change

Answer 8

80% of a SW system’s cost comes from changes that need to be made after initial deployment

Question 9

What is a local change

Answer 9

a change that affects only one component or one connector

Question 10

What is a non-local change

Answer 10

a change that affects more than one component or connector but retains the overall architecture

Question 11

What is an architectural change

Answer 11

a change to the underlying architecture (i.e. the fundamental ways that elements interact)

Question 12

How does an architecture enhance communication with stakeholders

Answer 12

the views that are created from the architecture enable communication by providing something a way for all types of stakeholders (technical and non-technical) to reason about the system

Question 13

How does an architecture define a set of constraints on the implementation

Answer 13

the set of prescribed elements must be implemented

the elements must interact in the prescribed fashion

each element must fulfill its responsibility to the other elements as dictated

Question 14

How does the architecture influence the organizational structure

Answer 14

• development teams are formed around different architectural structures
• the arch is the basis of the WBS
• maintenance teams are also formed around arch structures

Question 15

How does the arch allow for improved cost and schedule estimates

Answer 15

a top-down and bottom-up estimate can be done for each architectural structure. The best cost estimate of each structure is a consensus between top-down and bottom-up estimates. Then you sum those estimates over all the structures

Question 16

What is the benefit of the arch as a transferable/reusable model

Answer 16

• allows code to be reused and system to be built faster
• client will like the reduced cost
• can form a product line allowing a company to establish a vertical market

Question 17

What is a product line

Answer 17

a family of SW systems all built using the same set of reusable assets (i.e. the architecture)

Question 18

The main benefit of an arch in regards to using COTS or open source SW

Answer 18

allows architects and project managers to know what COTS or open source SW will be needed and how it needs to fit before we start the implementation.

Question 19

The 4 payoffs of using COTS or open source SW

Answer 19

• decreased time to market
• increased reliability
• lower cost
• flexibility

Question 20

What does it mean to restrict design vocabulary

Answer 20

we reduce the design complexity of the system by voluntarily restricting ourselves to a relatively small number of choices of elements an interactions

Question 21

6 benefits of restricting design vocabulary

Answer 21

• minimize design complexity
• enhance reuse
• simpler designs that are more easily understood
• more capable analysis
• shorter selection time
• greater interoperability

Question 22

How is the arch used as a basis for training

Answer 22

showing the module structures helps a new member learn the project structure

showing component-and-connector structures allows a new member to learn how the system is supposed to work and accomplish its job