HomeOps Platform – Interfaces¶
How does the system communicate?¶
Table of Contents¶
- Purpose and Scope of Interfaces
- Interface Design Principles
- Interface Categories
- Client ↔ Backend Interfaces
- Backend ↔ Data Zone Interfaces
- Backend ↔ External Services Interfaces
- Service ↔ Service Interfaces (Internal)
- Authentication, Authorization, and Trust Boundaries
- Error Handling and Failure Considerations
- Interface Evolution and Versioning
1. Purpose and Scope of Interfaces¶
The purpose of this document is to describe how the different components of the HomeOps Platform communicate with each other at a system level. In this context, an interface refers to a clearly defined boundary through which data, commands, or events are exchanged between components.
Interfaces are documented at an umbrella-project level to support modularity and long-term maintainability. Rather than focusing on implementation details or language-specific constructs, this document outlines the expectations, responsibilities, and assumptions that exist between interacting parts of the system.
This document does not aim to provide detailed API specifications, database schemas, or protocol-level definitions. Such details belong to the individual subprojects where the interfaces are implemented. Instead, the focus here is on identifying where interfaces exist, why they exist, and what kind of interaction they are expected to support.
By making interfaces explicit, the platform aims to reduce tight coupling between components, enable independent development, and allow future extensions or replacements without requiring fundamental changes to the overall system architecture.
2. Interface Design Principles¶
All interfaces within the HomeOps Platform are guided by a small set of design principles intended to keep communication predictable, secure, and adaptable as the system evolves.
Explicit contracts
Interfaces should define clear expectations regarding inputs, outputs, and responsibilities. Implicit assumptions between components are avoided in favor of well-defined interaction patterns.
Loose coupling
Components should depend on interfaces rather than concrete implementations. This allows individual parts of the system to be modified, replaced, or scaled independently without cascading changes across the platform.
Awareness of trust boundaries
Interfaces often cross trust boundaries, such as between client devices and backend services or between internal services and external systems. These boundaries must be acknowledged and reflected in interface design, particularly with respect to authentication and authorization.
Least privilege access
Interfaces should expose only the minimum level of access required for their intended use. Components interacting through an interface should not gain broader access to system resources than necessary.
Simplicity over completeness
Interfaces are designed to address current and clearly anticipated needs rather than hypothetical future requirements. Avoiding unnecessary complexity helps keep interfaces stable and easier to reason about over time.
Evolution without disruption
Interfaces should be designed with change in mind. When evolution is required, preference is given to approaches that minimize breaking changes and allow existing consumers to continue operating during transitions.
Together, these principles provide a common foundation for interface-related decisions across the platform, supporting both technical clarity and sustainable system growth.
3. Interface Categories¶
Not all interfaces within the HomeOps Platform serve the same purpose or operate under the same constraints. To reason about communication patterns more effectively, interfaces are grouped into categories based on their role, scope, and trust assumptions.
This categorization helps clarify:
- which components are allowed to communicate with each other,
- what kind of data flows are expected,
- and which interfaces require stricter security or stability guarantees.
The following interface categories are used throughout the platform.
Client-Facing Interfaces¶
Client-facing interfaces connect user-facing applications to backend services. These interfaces are typically accessed from client devices such as web browsers or mobile applications.
Characteristics of client-facing interfaces include:
- Exposure across a trust boundary
- Interaction initiated by user actions
- A strong emphasis on authentication, authorization, and input validation
These interfaces are considered part of the platform’s public surface and are designed with stability and clarity in mind.
Internal Service Interfaces¶
Internal service interfaces enable communication between backend services or internal components of the platform. They are not intended to be accessed directly by end users or client devices.
Typical characteristics include:
- Operation within a more restricted trust zone
- Narrower and purpose-specific access
- Assumptions about controlled runtime environments
Although internal, these interfaces are still explicitly defined to avoid hidden dependencies and to support future refactoring or scaling.
Data Access Interfaces¶
Data access interfaces mediate interactions between application logic and stateful components such as databases, data loggers, or file storage systems.
These interfaces:
- Abstract the underlying data storage mechanisms
- Enforce access constraints aligned with data ownership
- Limit direct exposure of persistent data to only those components that require it
By treating data access as a distinct interface category, the platform reinforces the separation between application logic and data persistence.
External Integration Interfaces¶
External integration interfaces connect platform components to services outside the HomeOps Platform, such as third-party APIs or external data sources.
These interfaces operate under limited control and higher uncertainty. As a result, they must account for:
- Variable availability
- Changing external contracts
- Failures beyond the platform’s control
Clear boundaries and defensive interaction patterns are emphasized to prevent external issues from propagating unnecessarily into the system.
This categorization provides a structured foundation for the more detailed interface descriptions that follow. Each subsequent section focuses on one category and discusses its specific assumptions, constraints, and design considerations.
4. Client ↔ Backend Interfaces¶
Client ↔ Backend interfaces define how user-facing applications interact with the core services of the HomeOps Platform. These interfaces represent the primary point of interaction between users and the system and therefore form a critical part of the platform’s public surface.
Communication across this interface is typically initiated by user actions, such as viewing data, submitting input, or triggering control operations. As a result, these interfaces must be designed to handle untrusted input and variable usage patterns.
Key characteristics of Client ↔ Backend interfaces include:
- Clear and stable contracts that define available operations and expected responses
- Explicit authentication and authorization requirements
- Validation and sanitization of all incoming data
- Well-defined error responses that do not expose internal implementation details
Client-facing interfaces are responsible for enforcing access boundaries. Client applications do not interact directly with internal services, data stores, or infrastructure components. Instead, all such interactions are mediated through backend services that apply business logic, access control, and consistency rules.
From an architectural perspective, the backend is treated as the authoritative source of truth. Client applications are considered consumers of backend-provided capabilities rather than peers with direct access to internal system resources.
5. Backend ↔ Data Zone Interfaces¶
Backend ↔ Data Zone interfaces govern how backend services access stateful components such as databases, data loggers, and file storage systems. These interfaces are internal to the platform but are subject to strict access and trust considerations due to the sensitivity and persistence of the data involved.
The Data Zone is intentionally isolated from direct client access. All data interactions must pass through backend services, which act as controlled intermediaries. This separation ensures that data access rules are applied consistently and that persistent data is not exposed beyond its intended scope.
Key considerations for Backend ↔ Data Zone interfaces include:
- Explicit ownership of data by specific backend services
- Narrowly scoped read and write permissions aligned with service responsibilities
- Clear separation between data access logic and application logic
- Protection against unintended coupling between services and underlying storage technologies
These interfaces abstract the details of data storage from higher-level components. Backend services interact with the Data Zone through well-defined access patterns rather than relying on shared assumptions about schemas, file structures, or storage behavior.
By treating data access as a distinct interface category, the platform reinforces the principle that persistent data is a protected asset. This approach supports future changes to storage implementations, backup strategies, or data retention policies without requiring widespread changes across the system.
6. Backend ↔ External Services Interfaces¶
Backend ↔ External Services interfaces describe how the HomeOps Platform interacts with systems and services that are outside its direct control. These interfaces include integrations with third-party APIs, external data providers, and hardware-specific systems such as energy monitoring or solar inverter platforms.
Unlike internal interfaces, external interfaces operate under conditions of limited trust and higher uncertainty. Availability, performance, and contract stability cannot be fully guaranteed by the platform. As a result, these interfaces must be designed defensively.
Key characteristics of Backend ↔ External Services interfaces include:
- Clear separation between internal logic and external dependencies
- Explicit handling of failures, timeouts, and partial responses
- Limited assumptions about availability and response consistency
- Isolation of external integrations to prevent cascading failures
Backend services act as adapters between external systems and the internal platform. External data is validated and transformed before being used internally, and platform-specific assumptions are not leaked to external dependencies.
By encapsulating external integrations behind well-defined interfaces, the platform reduces the impact of external changes and creates a clear boundary between controlled and uncontrolled system behavior.
7. Service ↔ Service Interfaces (Internal)¶
Service ↔ Service interfaces govern communication between internal backend services within the HomeOps Platform. These interfaces become relevant as the platform grows beyond a single backend component and responsibilities are distributed across multiple services.
Although internal, these interfaces are treated as explicit contracts rather than implicit implementation details. Clear definition helps prevent tight coupling and makes service boundaries visible and intentional.
Typical characteristics of internal service interfaces include:
- Communication within a restricted trust zone
- Narrowly scoped operations aligned with service responsibilities
- Clear ownership of data and functionality
- Assumptions about controlled deployment and runtime environments
Internal service interfaces are not exposed directly to clients. Any client-facing interaction is mediated through designated backend entry points that apply access control and validation consistently.
By defining service-to-service communication explicitly, the platform supports incremental decomposition of functionality. Services can be introduced, modified, or retired with minimal impact on unrelated components, as long as interface contracts are respected.
8. Authentication, Authorization, and Trust Boundaries¶
Interfaces within the HomeOps Platform frequently cross trust boundaries, such as between client devices and backend services, or between internal services operating in different network zones. As a result, authentication and authorization are treated as integral parts of interface design rather than as implementation details.
Each interface explicitly defines:
- who or what is allowed to access it,
- under which conditions access is granted,
- and which actions are permitted once access is established.
Authentication mechanisms are used to establish identity, while authorization rules determine the scope of allowed operations. These concerns are addressed separately to avoid implicit trust and overly broad access.
Trust boundaries identified at the network and system level are reflected in interface design. Interfaces that cross from a less trusted zone into a more trusted one are subject to stricter validation, access control, and monitoring requirements.
Backend services act as enforcement points for access control. Client-facing interfaces do not grant direct access to internal services or data, and internal service interfaces are scoped to operate only within defined trust zones.
This approach aligns interface behavior with the platform’s security model, ensuring that access control remains consistent across components and evolves in a controlled manner.
9. Error Handling and Failure Considerations¶
Interfaces must remain understandable and predictable not only during normal operation, but also in the presence of errors, partial failures, or unexpected conditions. In a distributed and modular system, failures are considered normal events rather than exceptional cases.
The HomeOps Platform adopts the following principles for error handling across interfaces:
- Errors are treated as part of the interface contract and are documented explicitly.
- Failure in one component should not propagate unnecessarily to unrelated parts of the system.
- Interfaces should provide clear and bounded error responses rather than exposing internal state or implementation details.
- Timeouts, unavailability, and partial responses are expected when interacting with external services.
Backend services are responsible for translating internal errors into interface-appropriate responses. Client-facing interfaces prioritize clarity and stability, while internal interfaces may expose more detailed error information within trusted boundaries.
By acknowledging failure as a normal condition, the platform encourages resilient interaction patterns and reduces the likelihood that localized issues escalate into system-wide failures.
10. Interface Evolution and Versioning¶
Interfaces within the HomeOps Platform are expected to evolve over time as requirements change, new components are introduced, and understanding of the system deepens. Interface design therefore considers not only current functionality, but also how changes can be introduced in a controlled and predictable manner.
Breaking changes to interfaces are treated as significant events. Whenever possible, interfaces should evolve in a backward-compatible way, allowing existing consumers to continue operating while new capabilities are introduced. This reduces the need for coordinated changes across multiple components and supports independent development.
Versioning is used as a communication tool rather than a purely technical mechanism. Changes to interfaces should be visible and intentional, making it clear to consumers when behavior, expectations, or guarantees have changed. The exact versioning strategy may differ between interfaces and is defined within the scope of individual subprojects.
Deprecation is preferred over immediate removal. When an interface or capability is no longer suitable, it should be phased out gradually, with clear guidance provided for migration to newer alternatives.
By approaching interface evolution deliberately, the platform aims to balance flexibility with stability. This supports long-term maintainability and ensures that the system can grow without accumulating hidden dependencies or forcing disruptive changes across components.