Chapter 9. Creating the Physical Design

Terms you'll need to understand:

• Tracing and logging

• Unhandled and structured exceptions

• Integration and interoperability

• ACID transactions

• Authorization and authentication security

• Latency and bandwidth

• Business Logic Layer (BLL)

• User Services Layer (USL)

• Data Access Layer (DAL)

• State management solutions

Techniques you'll need to master:

• Designing specifications for an application that logs events to the Windows event log

• Writing to the trace listener and configuring the trace while the application is deployed

• Handling all unhandled exceptions through the web.config and global.asax files in ASP.NET projects

• Understanding the importance of ACID transactions and determining which layers are best suited to invoke and/or participate in a transaction

• Administering role-based authorization on a project's subfolders through the web.config file

• Understanding when a Windows Form should be used instead of a Web form and vice versa

• Architecting a Web farm with effective use of firewalls and secure communications

• Implementing a service agent to provide an exposed interface that is open to a channel for remote access

• Consuming a service agent and providing a consistent interface so that it can be accessed similarly to data being gathered from an RDBMS

• Designing a global state management solution that is acceptable to user settings and server configurations

Have you ever attempted a large home-improvement project without a detailed plan? Maybe you sketched a diagram on a napkin and had a basic idea of what you wanted to build, but did not take measurements, get permits from the city, and so on. If so, you probably went to the local hardware store and purchased too many or too few materials. While building, you realized that what you originally had in mind wasn't feasible because of unforeseen circumstances. You might even have discovered that the end product was much cheaper to buy off the shelf or build with partially constructed pieces, which could have saved you time and money. Most of these problems could have been avoided or mitigated by developing a detailed work plan.

Chapters 7, "Creating the Logical Design," and 8, "Creating the Logical Data Model," covered creating the logical design, which is the stage directly after conceptual design. The logical design expands on the conceptual design by addressing the solution's structure without defining exact technology or class methods and properties. The physical design follows as an exact blueprint of what is to be created and how it is to be administered and deployed. The physical design defines specific servers, technologies, operating systems, constraints, and methods and properties of the business services that were designed in the logical design.

After the physical design is created, implementation begins. The specifications created during the physical design are used by those in the developer role during solution implementation. The physical design should be as thorough as possible, leaving nothing to question; however, there are possibilities for error and the physical design might need some adjustments after development has started. With adequate planning, any unknown risks associated with integration, availability, and scalability can be greatly diminished.