Welcome to APEX - The Adaptive Policy EXecution (Engine)

The APEX (Adaptive Policy Execution) policy engine is a fully featured policy engine that executes anything from simple to adaptive policies. An adaptive policy is one that can modify its behavior based on the current conditions of the network and systems. Adaptive policies have the following characteristics:

Are able to make decisions at runtime rather than simply selecting decisions described at policy definition time
Can use additional context information that was not provided in the incoming event or request
Can be adapted or self-adapt at runtime to modify decision making

The APEX policy engine accepts input events and requests from other components, routes the input to the appropriate policies, computes the policy results, and generates response events or actions to be processed by other components. The policies may be affected by information injected into the policy context as changes in business or domain goals, by information derived from previous executions of the policies, and by context information retrieved from other components (analytics, inventory, topology, etc.).

APEX connects to a Trigger System to receive events that can trigger a policy and to an Actioning System to send the result of a policy. The connection support various common technologies, such as messaging systems (Kafka, Websockets), file input/output, and standard input/output. APEX supports context (as additional information) for all events as well as inside the engine to support policies. Context information can be read from any outside source.

A policy is defined in a Universal Execution Policy Specification (UEPS), directly executable in an APEX engine. Higher-level policy specifications (or existing policy languages) can be easily translated in UEPS.

An APEX system can use multiple policy engines with different policies deployed on each of them. Context information is automatically shared between all engine instances. A simple deployment component is provided.

APEX Documentation

Document	Description
APEX Introduction	This is a short introduction to APEX to show its features and capabilities. Also available as stand-alone HTML and stand-alone PDF.
Publications	APEX is based on a theor called Unifying Policy Theory (UPT). Over the years, we have published a number of papers on APEX, context management, policy in general, and control loops. This is the list of all APEX and the most relevant other publications. We provide links to full text versions if possible. Also available as stand-alone HTML and stand-alone PDF.
APEX User Manual	The APEX user manual combines a set of guides and howto documents, all supporting the use of APEX. The guides and howto documents are provided as integrated documentation in the APEX site. Furthermore, we provide stand-alone documents in HTML and PDF.
APEX Policy Guide	The APEX policy guide combines a set of howto documents, all supporting APEX and policy, including how to write task and task selection logic. The howto documents are provided as integrated documentation in the APEX site. Furthermore, we provide stand-alone documents in HTML and PDF.
APEX Development Guide	The APEX developer guide combines a set of guides and howto documents, all addressing aspects for APEX developers. These documents look at APEX internals and how to extend build and extend the platform, and how to add applications. The guide and howto documents are provided as integrated documentation in the APEX site. Furthermore, we provide stand-alone documents in HTML and PDF.

APEX Modules and Projects

Name	Description	Useful for
auth	Policy, state, and task authoring for APEX. Important projects here are: cli-editor - The APEX CLI Editor cli-codegen - Code-generation tools	Policy Designers
plugins	Plugins for APEX that can be implemented with various 3PPs are implemented here. Most of the APEX engine and system functionality is realized using plug-ins. These plug-ins are loaded when an APEX policy engine is started. A configuration specifies which plugins to load. Important projects here are: plugins-executor - Execution environments for policy logic, such as Javascript, Java, JRuby, Jython, MVEL plugins-event - All event-related plugins: carrier technologies (Kafka, Websocket), event protocols (XML, IBeam) plugins-context - Everything for context: schema (for defining context) distribution (across policies and engines), locking (for writing to context items), persistence plugins-persistence - Everything needed for persistence (beside context), mainly JPA plugins for Eclipselink and Hibernate	Plugin developers
services	The main services of APEX, deployment independent. Important projects here are: services-engine - APEX engine service	Service developers, Deployers
core	The core of APEX, deployment independent. Important projects here are: core-engine - The APEX policy execution engine core-infrastructure - Common non-functional components for APEX core-deployment - The APEX policy deployer core-protocols - Protocols used to transfer information between components in APEX	Core APEX developers
context	The context handling framework of APEX. Important projects here are: context-management - Context management for Apex policy execution context-test - Test context date for testing	Core APEX developers
model	The model for APEX, it comtains definitions of all APEX concepts, also has handling for APEX policy models. Important projects here are: model-api - The APEX Model API with programatic access to a policy model basic-model - Basic Models used and model handling in Apex event-model - Event Models used in APEX policy-model - Policy Models used in APEX engine-model - Engine Models used in APEX context-model - Context Models used in APEX model-utilities - Common non-functional Apex Model Utilities	Core APEX developers, Application developers (Model API)

APEX Resources

Resource	Description
APEX Source (ONAP)	The source of APEX is hosted part of the ONAP Policy Framework.
APEX Issue Management (Github)	Issues with the APEX software and integrated documentation are managed here.