第2章計算論的思考と設計の再利用性

The enterprise technology architecture (ETA) is a comprehensive framework that defines the structure, components, and interrelationships of an organization’s technology systems to support its business processes and objectives. In general, the ETA guides the development and support of an organization’s information systems⁴ and technology infrastructure. Therefore, it characterizes the organization’s application, data, and technology infrastructure architectures and describes their models. The technology (virtual infrastructure) supports the execution of information systems services, which in turn support business functions and related services. Application, data, and technology infrastructure architecture models may be described via blueprints at different levels of abstraction, including presentation, conceptual, logical, and physical. Layering and componentization heuristics play an important role in structuring these models.

The abstraction level indicates the extent to which a design is distanced from tangible technological details. This level of abstraction can differ across various architectural fields, but four main levels are widely recognized:

1. Presentation: At this level, architecture is simplified into a form to streamline the communication of essential ideas, particularly to business executives. Distilling complex architectural diagrams into more straightforward, high-level visuals ensures that the core messages are conveyed effectively.

2. Conceptual: This level offers a more structured view of architecture, deliberately omitting many specifics. The rationale for not including certain details is that they may not be relevant to the diagram’s intended purpose or are yet to be decided.

3. Logical: The architecture is depicted in detail but remains uncertain of specific technologies. It aims to give a full outline without committing to the particular technologies that will be employed for the final build.

4. Physical: This level focuses on the actual technological specifics used or to be used in the architecture’s realization, making it the most concrete representation of the four.

Business operations are commonly articulated through a value chain framework, a concept originating from manufacturing practices. Analogous to the manufacturing industry where raw materials like steel are transformed into various components, each step in the value chain plays a role in creating a finished product, such as a car. In our approach, we’ve utilized the componentization heuristic to break down business operations into distinct steps constituting the elements of a value chain. Additionally, the layering heuristic has been applied to structure the value chain as layers of elements. Each layer in this model relies on the output of the preceding layer to perform its specific function. This methodology enhances the understanding of how value is sequentially added throughout the business process.

The application architecture is a subset of the enterprise solution architecture that includes a process to architect and design the application architecture as well as the actual application architecture model, which represents the content of the application architecture. Application architecture helps organizations decide how to invest in new software and systems. It makes sure that any new software being looked at, designed, or put into use can work well with the systems the organization already has. This includes brand-new software, updates to old software, making old software better, and buying and updating software packages.

4 Information systems architectures combine the use of application and data architecture details and specify control and data flow necessary to operate the systems.

Figure 2.16 illustrates a conceptual application architecture model of the sample trading business model that was introduced earlier in this section. The goal of a conceptual application architecture is to demonstrate how members of the organization interact with the application architecture from different locations when invoking business processes. This example illustrates three distinct offices accommodating a diverse range of users, including management, trading, IT, and others.

Figure 2.17 takes the conceptual trading application architecture a bit further and describes what one of the alternative application architectures may look like at the logical level. The goal of the logical application architecture is to identify the various functional blocks within the architecture without getting into the details of how they connect with and/or use each other.