Architecture Lifecycle Issues

Architecture Based Process

• Establish business case for the system. e.g. Product cost, time to market.
• Understand the requirements
  • Use cases, prototypes
  • Quality attributes
  • Commonality & variability from previous/future systems - domain analysis.
• Develop the architecture - use tactics, styles.
• Document the architecture - using variety of views and ADL.
• Analyse or evaluate the architecture.
• Implement product based on the architecture.
• Ensure that implementation conforms with architecture.

Process Recommendations

• Architecture should be a product of a single architect or a small group of architects with a single leader.
• Arch should have both functional reqs and an articulated, prioritized list of quality attributes.
• Arch should be well documented with atleast one static view and one dynamic view.
• Arch should be circulated to all stakeholders who should actively review.
• Arch should be analysed for quantitative measures and formally evaluated for qualitative properties.
• Should lend itself to incremental implementation via creation of a skeletal system.

Global Analysis

• The purpose of global analysis is to analyse the factors that influence the architecture and develop strategies for accommodating these factors in the architecture design.
• Three types of factors:

1. Organizational factors
2. Technological factors
3. Product factors

Process

Analyse factors

• 1. Identify and describe factors
  • Consider those that have significant global influence.
  • Can factor be localized or is it truly global ?
• 2. Characterize the flexibility and changeability of the factors
  • Can factor be changed, modified, influenced.
  • How often will it change ? How likely ?
• 3. Analyse the impact of factors
  • Other factors, component, design decisions.

Develop Strategies

• 1. Identify issues and influencing factors
  • Identify handful of important issues that are influenced by factors and their changeability.
  • Usually several factors affect an issue and when they conflict - we must negotiate a change in them.
  • Difficult to satisfy factor, expensive factor.
• 2. Develop solutions and specific strategies
  • Reduce or localize factor's influence.
• 3. Identify related strategies
  • Dont repeat strategies identified with more than one issue. Reference them.

Organisational Factors

1. Management
2. Staff skills

• e.g. Analyze factors
• experience in multithreading.
• Only one developer has skill.
• Flexibility: Subject area is too complex for only training.
• Impact: There is a moderate impact on meeting performance.
• Strategies
• Only 1 developer
• Strategy: avoid use of multiple threads.

1. Process and development environment
2. Development schedule
3. Development budget

Technological Factors

1. General purpose hardware e.g CPU, mem, disk
2. Special purpose hardware e.g. probe
3. Software technology e.g. OS, language,
4. Architecture technology - e.g product line, DSL's.
5. Standards - OS interface, data formats, coding conventions.

Product Factors

1. Functional Features
2. UI
3. Performance
4. Dependability
5. Failure detection
6. Service - maintenance
7. Product cost

Issue: Easy Addition and removal of features Factors: O4.1 (Org Factor) : TIme to market short P1 (Prod factor) : New varieties added every 3 years. Solution: Use separation of concerns Strategy: Separate components and modules across dimensions of concern Related Strategy: See: encapsulate general purpose hardware.