第10章エンタープライズアーキテクチャーとソリューションアーキテクチャーの管理

A blueprint is a high-level plan used in the development stage, and an enterprise architecture (EA) is a conceptual blueprint that defines the structure and operation of organizations. Design modeling provides a variety of different views of the system like architecture plans for the enterprise. Examples of a design-centric architectural style are microservices. An example of a corresponding implementation-centric implementation style is REST Services. When the problem appears, an architectural pattern embodies architectural design decisions that are applicable to a recurring design problem parameterized to account for different solution development contexts.

A design pattern relates to common design structures and practices that enable the creation of reusable software. An example of a design pattern is a singleton. A singleton restricts the instantiation of a class and ensures that only one instance of the class exists (e.g., a scoreboard object in a game should be derived from a singleton class to ensure that there is only one scoreboard object and one set of scores for the players at any given time). The enterprise architecture scope includes:

• Enterprise scope: higher-level patterns that can be applied to the overall structure of the enterprise

2 There may be several implementation-centric patterns that realize a given design-centric pattern.

• Solution scope: the pattern that can be applied to a single solution or system

• Domain scope: the pattern that can be applied to a specific domain

A pattern hierarchy applies at all levels of scope, but variants of the higher-level patterns add additional embedded patterns that may be documented as a given enterprise architecture (EA) model, which gets described more specifically at the portfolio or system levels. This is similar to the map of the city being part of the map of a region within the map of the world, as shown in Figure 10.2.

In object-oriented programming languages such as Java, a singleton class can have only one object at a time. The purpose of a singleton class is to restrict the number of object creations to only one, which ensures access control to resources. A Java singleton class (Figure 10.3) is a corresponding implementation-centric example of an idiom that implements a singleton design pattern and allows one instance of a Java class to exist, as in Figure 10.4.

Problems and the need for solutions vary depending on the region of the world where people are located. For example, economically developing regions like Africa or parts of the Middle East do not have fiber-optic networks as sophisticated as the ones deployed in Europe, where extensive investments in infrastructure have been made. This disparity impacts not only access to the Internet but also the potential for growth in education, technology, and health-care systems. As a result, solutions to these problems are tailored to address the unique needs in these regions. Addressing these needs might involve developing alternative solutions like satellite Internet or mobile broadband networks, which can provide connectivity. However, these solutions need to be cost-effective and scalable to ensure they meet the population’s needs.

From a top-down standpoint (e.g., enterprise, portfolio, or project), architecture may appear in different levels of focus. The architecture areas span the whole enterprise and include various domains of architecture, such as business, information, application, and technology domains. The enterprise domains in the three standpoints are illustrated in Figure 10.5.

Patterns may be described using a pattern taxonomy and stored in a pattern repository or catalog. A pattern catalog is a collection of patterns that are organized according to specific characteristics and according to how the relationships between them are defined. Figure 10.6 illustrates the general structure of a pattern catalog. A pattern catalog allows the bookkeeping of clusters of patterns at various levels of specialization (i.e., analysis and design model patterns versus implementation patterns).

One example of a business architecture pattern that includes a generalization of business service composition and a pattern used to describe the sequencing of business services is business service orchestration. If the data does not include data presentation, then business service orchestration provides additional logic to process this kind of data. Another example of a business architecture pattern that focuses on the observed sequence of messages exchanged by peer services when performing a unit of work is called business service choreography. Figure 10.7 illustrates how various business architecture design patterns (e.g., exchange, shipment, order, and payment) may be combined via inheritance and composition to create a “buyer-seller” design pattern.