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
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High Performance
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Load balancing, network address translation, proxy servers
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Introduce concurrency; increase resources; multiple copies
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High Availability
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Redundant processors, networks, databases, and software; load balancing
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Active redundancy; transactions; introduce concurrency
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Scalability
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Allow for horizontal and vertical scaling; load balancing
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Abstract common services; adherence to defined protocols; introduce concurrency
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Security
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Firewalls; public/private key encryption across public networks
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Limit access; integrity; limit exposure
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Modifiability
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Separation of browser functionality, database design, and business logic into distinct tiers
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Abstract common services; semantic coherence; intermediary; interface stability
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