This is because the diagram shows the three main categories of relationships in ArchiMate: structural relationships, which model the static construction or composition of concepts; dependency relationships, which model how elements depend on or use other elements; and dynamic relationships, which model the temporal or causal connections between elements.

According to the conceptual model of architecture description from ISO/IEC 42010, an architecture view is a representation of a system from the perspective of a set of concerns. An architecture viewpoint is a specification of the conventions and rules for constructing and using an architecture view. A and B in the diagram correspond to these concepts respectively.

Comprehensive and Detailed in Depth Explanation:APrinciplein ArchiMate is ahigh-level guidelinethat directsdecision-making and architecture development. It is aspecialization of a Constraint, meaning that it restricts behavior in a way that aligns with organizational goals.
TheArchiMate 3.2 SpecificationdescribesPrinciplesasspecific constraintsthat apply to enterprise architecture and governance.
References:
* Archi User Guide
* ArchiMate 3.2 Specification

Based on the ArchiMate 3 documents or objectives, a realization relationship indicates that an entity plays a critical role in the creation, achievement, sustenance, or operation of a more abstract entity. A serving relationship models that an element provides its functionality to another element. The diagram should use a realization relationship from the Risk Assessment service to the Enterprise Risk Management process to indicate that the service realizes the process. The diagram should also use a serving relationship from the Risk Measurement application to the Risk Assessment service to indicate that the application serves the service.

This is because a grouping is a composite element that aggregates or groups other elements based on some common characteristic or purpose. A course of action is a motivation element that represents an approach or plan for achieving some goal. An aggregation is a structural relationship that models the whole-part hierarchy between elements. A contract is a passive structure element that represents a formal or informal specification of an agreement between a provider and a consumer that specifies the rights and obligations associated with a product or service.
ased on the ArchiMate 3 documents or objectives, a grouping is a composite element that consists of other concepts, from one or more aspects or layers of the ArchiMate language. A grouping can be used to model a logical or physical grouping of elements that belong together based on some criteri a. A grouping can itself aggregate or compose other groupings, leading to a hierarchy of these elements.