The Benefits of Architecting
In general terms, architecting is a key factor in reducing cost, improving quality, supporting timely delivery against schedule, supporting delivery against requirements, and reducing risk. In this section, we focus on more specific benefits that contribute to meeting these objectives.
Also, because architects sometimes have to justify their existence, this section provides some useful ammunition for treating architecting as a critical part of the software development process.
Architecting Addresses System Qualities
The functionality of the system is supported by the architecture through the interactions that occur among the various elements that comprise the architecture. One of the key characteristics of architecting, however, is that it is the vehicle through which system qualities are achieved. Qualities such as performance, security, and maintainability cannot be achieved in the absence of a unifying architectural vision; these qualities are not confined to a single architectural element but permeate the entire architecture.
To address performance requirements, for example, it may be necessary to consider the time for each component of the architecture to execute and also the time spent in intercomponent communication. Similarly, to address security requirements, it may be necessary to consider the nature of the communication among components and introduce specific security-aware components where necessary. All these concerns are architectural and, in these examples, concern themselves with the individual components and the connections among them.
A related benefit of architecting is that it is possible to assess such qualities early in the project life cycle. Architectural proofs of concept are often created to specifically ensure that such qualities are addressed. Demonstrating that such qualities are met through an actual implementation (in this case, an architectural proof of concept) is important because no matter how good an architecture looks on paper, executable software is the only true measure of whether the architecture has addressed such qualities.
Architecting Drives Consensus
The process of architecting drives consensus among the various stakeholders because it provides a vehicle for enabling debate about the system solution. To support such debate, the process of architecting needs to ensure that the architecture is clearly communicated and proved.
An architecture that is communicated effectively allows decisions and trade-offs to be debated, facilitates reviews, and allows agreement to be reached. Conversely, an architecture that is poorly communicated does not allow such debate to occur. Without such input, the resulting architecture is likely to be of lower quality. Clearly, an important aspect of communicating the architecture effectively is documenting it appropriately. This topic is a primary concern for the architect and is the subject of Chapter 4, "Documenting a Software Architecture."
On a related note, the architecture can drive consensus between architects (and their vision) and new or existing team members as part of training. Again, the architecture must be communicated effectively for this benefit to be achieved. Development teams with a good vision of what they are implementing have a better chance of implementing the product as desired.
Driving consensus is also achieved by validating that the architecture meets the stated requirements. As mentioned in the preceding section, the creation of an executable proof of concept is an excellent way of demonstrating that the architecture meets certain run-time qualities.
Architecting Supports the Planning Process
The process of architecting supports several disciplines. Clearly, it supports the detailed design and implementation activities, because the architecture is a direct input to these activities. In terms of the benefits that the process of architecting brings, however, arguably the major benefits are those related to the support provided to project planning and project management activities in general—specifically scheduling, work allocation, cost analysis, risk management, and skills development. The process of architecting can support all these concerns, which is one of the main reasons why the architect and the project manager should have such a close relationship.
Much of this support is derived from the fact that the architecture identifies the significant components in the system and the relationships among them. Consider the UML component diagram in Figure 2.8, which has been kept deliberately simple for the purposes of this discussion. This figure shows four components with dependencies among them.
Figure 2.8 UML Component Diagram Showing Architecturally Significant Elements
For the purposes of this discussion, consider a simple case in which each component is always implemented in its entirety (that is, we do not create partial implementations of each element, and no separation of interface from implementation exists). In terms of scheduling, the dependencies imply an order in which each of these elements should be considered. From an implementation perspective, for example, the dependencies tell you that the Error Log component must be implemented before anything else, because all the other components use this component. Next, the Customer Management and Fulfillment components can be implemented in parallel because they do not depend on each other. Finally, when these two components have been implemented, the Account Management component can be implemented. From this information, you can derive the Gantt chart (one of the conventional planning techniques used by a project manager) shown in Figure 2.9. The duration of each of the tasks shown does require some thought but can be derived partially from the complexity of each of the architectural elements.
Figure 2.9 Gantt Chart Based on Dependencies among Architecturally Significant Elements
The architect can also assist in the cost estimation for the project. The costs associated with a project come from many areas. Clearly, the duration of the tasks and the resources allocated to the task allow the cost of labor to be determined. The architecture can also help determine costs related to the use of third-party components to be used in the delivered system. Another cost is derived from the use of particular tools that are required to support the creation of the architectural elements. Architecting also involves prioritizing risks and identifying appropriate risk mitigation strategies, both of which are provided as input to the project manager.
Finally, the architecture identifies discrete components of the solution that can provide input in terms of the skills required on the project. If appropriately skilled resources are not available within the project or within the organization, the architecture clearly helps identify areas in which skills acquisition is required. This acquisition may be achieved by developing existing personnel, outsourcing, or hiring new personnel.
Architecting Drives Architectural Integrity
One of the primary objectives of the process of architecting is making sure that the architecture provides a solid framework for the work undertaken by the designers and implementers. Clearly, this objective is more than simply conveying an architectural vision. To ensure the integrity of the resulting architecture, the architect must clearly define the architecture itself, which identifies the architecturally significant elements, such as the components of the system, their interfaces, and their interactions.
The architect must also define the appropriate practices, standards, and guidelines that will guide the designers and implementers in their work. Another objective of architecting is eliminating unnecessary creativity on the part of the designers and implementers, and this objective is achieved by imposing the necessary constraints on what designers and implementers can do, because deviation from the constraints may cause breakage of the architecture. Still another aspect of architecting that helps ensure architectural integrity is the adoption of appropriate review and assessment activities that confirm adherence to architectural standards and guidelines by designers and implementers.
We discuss architecture assessment further in Chapter 8, "Creating the Logical Architecture," and Chapter 9, "Creating the Physical Architecture."
Architecting Helps Manage Complexity
Systems today are more complex than ever, and this complexity needs to be managed. As mentioned earlier in this chapter, because an architecture focuses on only those elements that are significant, it provides an abstraction of the system and therefore provides a means of managing complexity. Also, the process of architecting considers the recursive decomposition of components, which is clearly a good way of taking a large problem and breaking it down into a series of smaller problems.
Finally, another aspect of managing complexity is using techniques that allow abstractions of the architecture to be communicated. You might choose to group components into subsystems or to separate interfaces from implementation, for example. The adoption of industry standards that allow abstractions to be expressed, such as UML, is commonplace in the industry today for documenting the architecture of software-intensive systems.
Architecting Provides a Basis for Reuse
The process of architecting can support both the production and consumption of reusable assets. Reusable assets are beneficial to an organization because they can reduce the overall cost of a system and also improve its quality, given that a reusable asset has already been proved (because it has already been used).
In terms of asset consumption, the creation of an architecture supports the identification of possible reuse opportunities. The identification of the architecturally significant components and their associated interfaces and qualities supports the selection of off-the-shelf components, existing systems, packaged applications, and so on that may be used to implement these components.
In terms of asset production, the architecture may contain elements that are, by their very nature, applicable outside the current system. The architecture may contain an error logging mechanism that could be reused in several other contexts. Such reuse generally is opportunistic, whereas a strategic reuse initiative considers candidate assets ahead of time. We touch on this topic in Chapter 10, "Beyond the Basics."
Architecting Reduces Maintenance Costs
The process of architecting can help reduce maintenance costs in several ways. First and foremost, the process of architecting should always ensure that the maintainer of the system is a key stakeholder and that the maintainer's needs are addressed as a primary concern, not as an afterthought. The result should be an architecture that is appropriately documented to ease the maintainability of the system; the architect also ensures that appropriate mechanisms for maintaining the system are incorporated and considers the adaptability and extensibility of the system when creating the architecture. In addition, the architect considers the skills available to maintain the system, which may be different from those of the team members who created the system.
The architect should consider the areas of the system that are most likely to require change and then isolate them. This process can be fairly straightforward if the change affects a single component or a small number of components. Some changes, however, such as those relating to system qualities such as performance or reliability, cannot be isolated in this way. For this reason, the architect must consider any likely future requirements when architecting the current system. Scaling up a system to support thousands of users rather than the tens of users for which the system was originally designed may not be possible without changing the architecture in fundamental ways, for example.
The issue of maintainability is a primary concern only for those systems that will evolve over time, not for systems whose purpose is to provide a tactical solution and whose life is limited.
Architecting Supports Impact Analysis
An important benefit of architecting is that it allows architects to reason about the impact of making a change before it is undertaken. An architecture identifies the major components and their interactions, the dependencies among components, and traceability from these components to the requirements that they realize.
Given this information, a change to a requirement can be analyzed in terms of the impact on the components that collaborate to realize this requirement. Similarly, the impact of changing a component can be analyzed in terms of the other components that depend upon it. Such analyses can greatly assist in determining the cost of a change, the impact that a change has on the system, and the risk associated with making the change.