Declarative Application Environment

Description

The Declarative Application Environment (DAE) is a standardized framework within 3GPP specifications that provides a declarative interface for applications to interact with network functions and services. Unlike traditional imperative APIs where applications issue specific commands to control network behavior, DAE allows applications to declare their desired outcomes, intents, or policies, and the network autonomously determines how to fulfill these declarations. This paradigm shift enables greater abstraction, simplifies application logic, and reduces the coupling between applications and underlying network implementations.

Architecturally, DAE operates as a middleware layer between applications and network functions, typically implemented within the Service Capability Exposure Function (SCEF) or Network Exposure Function (NEF) in 5G systems. It consists of several key components: a declarative API gateway that receives and validates application declarations, a policy engine that interprets these declarations into network-specific actions, a resource manager that maps declarations to available network resources, and a monitoring component that ensures declared outcomes are maintained. The framework supports various declaration types including quality of service requirements, mobility policies, security constraints, and service level objectives.

DAE works by receiving structured declarations from applications through RESTful APIs or message-based interfaces. These declarations are expressed in standardized data models defined in 3GPP specifications, typically using JSON or XML formats. The DAE system processes these declarations through several stages: validation against network capabilities and policies, translation into network-specific configuration commands, negotiation with network functions to allocate resources, and continuous monitoring to ensure the declared state is maintained. When network conditions change, DAE can automatically adapt configurations to preserve the declared outcomes without requiring application intervention.

The framework's role in the network is multifaceted: it serves as an abstraction layer that hides network complexity from applications, enables intent-based networking principles in mobile networks, facilitates network automation by reducing manual configuration, and supports dynamic service creation. DAE is particularly valuable in scenarios requiring network slicing, edge computing, and IoT services where applications have specific requirements but shouldn't need detailed knowledge of radio access or core network implementations. It integrates with existing 3GPP mechanisms like Policy and Charging Control (PCC), Network Slice Selection Function (NSSF), and User Plane Function (UPF) to enforce declared policies across the network infrastructure.

Purpose & Motivation

DAE was created to address the growing complexity of integrating applications with mobile networks, particularly as networks evolved toward 5G with capabilities like network slicing, edge computing, and massive IoT. Traditional imperative APIs required applications to have detailed knowledge of network internals and to manage complex state machines, which increased development complexity, created tight coupling between applications and specific network implementations, and made it difficult to adapt to network changes or failures. The declarative approach simplifies application development by allowing developers to focus on what they want to achieve rather than how to achieve it through specific network commands.

Historically, network exposure in 3GPP systems evolved from basic Parlay X web services in early releases to more sophisticated Service Capability Exposure Function (SCEF) in 4G and Network Exposure Function (NEF) in 5G. However, these approaches still largely followed imperative models where applications needed to issue specific commands for network actions. DAE represents a paradigm shift inspired by similar approaches in cloud computing and software-defined networking, recognizing that as networks become more programmable and virtualized, a higher-level abstraction layer is needed to manage complexity and enable true network automation.

The technology solves several key problems: it reduces the cognitive load on application developers by abstracting network complexity, enables more robust and adaptive applications that can survive network changes without reprogramming, facilitates network automation by allowing the network to optimize how to fulfill application requirements, and supports new business models where network capabilities can be exposed as declarative services. By addressing these challenges, DE enables faster service innovation, reduces operational costs, and makes advanced network features more accessible to application developers without requiring deep telecommunications expertise.

Key Features

• Declarative API interface for specifying desired network outcomes
• Policy-based translation of declarations to network configurations
• Integration with 3GPP network functions including NEF and SCEF
• Support for network slicing and quality of service declarations
• Continuous monitoring and adaptation to maintain declared states
• Standardized data models for application-network communication

Evolution Across Releases

Defining Specifications