13.5 Achieving Quality Goals

Together the elements we have described allow the Web-based e-commerce system to achieve its stringent quality goals of security, high availability, modifiability, scalability, and high performance. How they do this is shown in Table 13.3.

Table 13.3. How the Web e-Commerce Architecture Achieves Its Quality Goals


How Achieved


High Performance

Load balancing, network address translation, proxy servers

Introduce concurrency; increase resources; multiple copies

High Availability

Redundant processors, networks, databases, and software; load balancing

Active redundancy; transactions; introduce concurrency


Allow for horizontal and vertical scaling; load balancing

Abstract common services; adherence to defined protocols; introduce concurrency


Firewalls; public/private key encryption across public networks

Limit access; integrity; limit exposure


Separation of browser functionality, database design, and business logic into distinct tiers

Abstract common services; semantic coherence; intermediary; interface stability

    Part Two: Creating an Architecture
    Part Four: Moving From One System to Many