# KGrid Common Activation Specifications

# Introduction

The Activator is a reference implementation of the activation spec. This specification focuses on client interactions and integration with with various client systems. See runtime adapter development guide for more on how an Activator manages and interacts with runtimes.

# Responsibilities of the Activator (...)

  • provide access (HTTP Restful API) to the services (exposed as endpoints) from knowledge objects deployed to the Activator
  • Provide status for associated runtimes, KOs deployed, and the Activator itself
  • Allow KOs to be loaded/activated from local and remote source (in suitable runtimes)
  • Manage and interface with suitable runtimes — embedded, native, remote (proxy)
  • Enforce some aspects of trust, provenance, and reproducibility via policy, validation, and tracing/logging.

# Purpose

Systems are being designed and built to help move biomedical knowledge into practice more quickly, more broadly, more accurately than ever before. Those systems will rely on long-term access and management of compound digital objects within digital repositories, and deployment and integration of these objects as services in a broad class of runtimes (See KGRID Activation Spec). This requires infrastructural standards and specifications that enable integration at scale.

This spec represents our recommendations on how to meet the following needs:

# ...

# Status of this document

This document is draft of a potential specification. It has no official standing of any kind and does not represent the support or consensus of any standards organisation.

# 1. Conformance

As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.

The key words may, must, must not, should, and should not are to be interpreted as described in [RFC2119].

# 2. Terminology

See [KOIO] for matching ontology terms....

# Knowledge Object (KO):

A collection of metadata and binary files that together have a unique identifier (including version identifier). There are three required file types: a service description, a deployment description, and one or more payload files implementing the service described by the service description, deployable using the information in the deployment description. See [Activation Spec] for details of the roles of the these files.

KOIO term — koio:KnowledgeObject

# Shelf:

The Knowledge Grid provides repository capabilities using a abstraction called the "Shelf." KOs are added to and managed for storage and retrieval through the Shelf API. Different concrete implementations of physical storage for KOs are available and not all capabilities are implemented in every component. See Shelf API.

# KO Endpoint:

A service path exposed by a particular knowledge object. Takes the form /naan/name/endpoint.

# Archival Resource Key (ARK):

The Knowledge Grid currently uses ARK identifiers natively which interoperate with EZID and top-level resolvers like Name2Thing and Identifiers.org. (Support for other identifiers like DOIs is planned).

# Manifest:

A representation of a collection knowledge object resources. The minimal representation is an array of KO metadata JSON-LD objects with an @id property.

# Activation:

THe process of deploying an implementation of a KO into a suitable runtime enviromnment in order to make the service endpoints (described in the service description available in the Activator API for use by client applications.

# Runtime

An environment capable of running the code for a particular class of KOs. Runtimes may be embbeded in an (custom) Adapter, or may communicate with the Activator through a (custom) Native or Proxy Adapter. THe refence imlementation of the Activator ships with an embedded Javascrip-runtime Adapter; also see Activator/Runtime deployment guide

# Adapter

Adapters allow particular Runtimes to interact with the Activator in order to deploy and run the code from a KO. An Adapter may handle initialization and registration of a runtime, provide access to the overall activation context and active endpoints, route client requests to KO Endpoints, and shutdown. Adapters implement the Adapter interface. See Developing Runtimes and the documentation for your specific Runtime/Adapter combination.

# 3. APIs

# Request API

The Request API exposes the micro-API for the services provide by each KO.

# Service Description
GET /kos/{naan}/{name}/sevice HTTP/1.1
Accept: application/json

The OpenAPI 3 service description returned describes all the endpoints implemented by this KO.

# Request (for each endpoint)
POST /kos/{naan}/{name}/{endpoint} HTTP/1.1
Accept: application/json
Content-type: application/json


Accept: and Content-type: headers are required, and should be application/json

(proposed) Allow any mime-type specified in service description.

# Response:

The response is wrapped in a JSON object. The actual KO result is available under the result: key.

HTTP/1.1 200 OK
Content-type: application/json
  "result": {
    "cvdrisk": {
      "total": 0.0026555542778455843,
      "chd": 0.0017632437883150498,
      "nonchd": 8.923104895305345E-4
  "info": {
    "ko": {
      "@id": "score-calc",
      "@type": "koio:KnowledgeObject",
      "identifier": "ark:/score/calc",
      "version": "v0.3.0",
      "title": "Ten-year Fatal Cardiovascular Risk Calculation based on SCORE project (Example KO - Bundled with a npm package) ",
      "description": "Estimating ten-year risk of fatal cardiovascular disease based on SCORE project. This version bundled the javascript code with externalized data files and a Node.js library of 'lodash'",
      "keywords": [
        "SCORE, ten-year",
        "Cardiovascular risk",
      "hasServiceSpecification": "service.yaml",
      "hasDeploymentSpecification": "service.yaml",
      "hasPayload": "dist/main.js",
      "@context": [
    "inputs": {
      "age": 48,
      "gender": "Female",
      "risk": "low",
      "sbp": 120,
      "cholesterol": 8,
      "smoker": false

(proposed) Return KO output and link to provenance, tracing, etc. Response code: HTTP/1.1 200

# Errors:

A custom problem details resource is returned and the KO problem details or exception message will be included in the Detail: property.

  "Status": "500 Internal Server Error",
  "Instance": "uri=/score/calc/v0.3.0/score",
  "Title": "Error",
  "Time": "Fri Jun 19 16:21:23 UTC 2020",
  "Detail": "JSON parse error: Unexpected character ('{' (code 123)): was..."

(proposed) Use Problem Details for HTTP APIs — rfc7807 and wrap any underlying KO response problem details.

# KO endpoint micro-APIs

The KO micro-API should be completely specified by the OpenAPI 3 service description. Clients rely on the service to use the API.

  • Each KO endpoint must accept inputs as spec'ed by the service description for a specific mime-type.
  • KO endpoints may do their own validation. They should not rely entirely on (proposed) Activator validation
  • Each KO endpoint must produce outputs as spec'ed by the service description for a specific mime-type. An output schema should be specificied. If not clients will have to handle outputs of arbitrary complexity.
  • If the knowledge object can't service the request it should use a well-defined scheme for responses (codes, error messages, etc.) The activator wraps KO error responses unchanged.
  • Individual KOs and endpoints must be stateless.
  • KOs may specifiy and use any properties in the deployment description depending on the particualr runtime.
  • Endpoint paths may be arbitrarly complex within the KO but must be unique.
  • Each KO may have multiple endpoints as long as the full path is unique.

# Activation API

# Endpoint resources




# Activation on startup

# Loading the shelf
  • If kgrid.shelf.manifest is set, the activator (shelf) will try to populate the shelf from the specified manifest(s).
  • Existing KOs on the shelf will not be deleted and may be overwritten.
# (proposed) If kgrid.activator.allowRuntimeImport is true
  • While running the Activator packaged KO (zip file) can be uploaded to the /kos endpoint to add a KO to the shelf
  • While running the Activator a manifest (json or yaml) can be POSTed to the /kos endpoint to initiate loading of one or more KOs from an external path (See Loading KOs onto the Shelf in the Kgrid Shelf documentation))

As KOs are added to the shelf, a warning is logged for each KO that is unreadable or malformed (e.g. missing metadata.json or deployment description)

# (proposed) If kgrid.activator.autoActivateOnStartup is true

Currently behaves as if kgrid.activator.autoActivateOnStartup is true by default

  • On startup the Activator attempts to activated every KO on the shelf

Once a KO has been activated, any activated endpoints will remain functional even if the KO is deleted, unless or until the activation state is refreshed (using /refresh or /refresh/{naan}/{name}). Likewise new KOs added to the shelf will NOT be activated unless or until the activation state is refreshed (using /refresh or /refresh/{naan}/{name}).

# Runtime activation via /refresh
  • /refresh — all current activations are discarded and the startup activation sequencce tries to activate every KO on the shelf
  • /refresh/{naan}/{name} — all current activations for the default version given KO are discarded and the KO is reactivated
  • /refresh/{naan}/{name}/{version} — all current activations for the given version KO are discarded and the KO is reactivated
# On every activation
  • When a KO is activated, a warning is logged for every endpoint that cannot be activated
  • (verify) If two endpoints have identical coordinates (/{naan}/{name}/{version}/{endpoint}) the second endpoint will not be loaded and a warning will be logged. Compliant implementations must not allow multiple endpoints and must not have endpoint unspecified request routing behavior.
  • Each activated endpoint is provided with a context object containing global activation properties and a means to resolve and access other endpoints in the same runtime or activator.

# Shelf API (read-only)

An Activator must implement at least the read-only portion of the Shelf API. This includes listing KOs, returning representations of indivdual KOs (e.g. metadata only, with links to key components).

(proposed) An activator must provide a resource representation for the knowledge object that includes activation status and endpoints.

(proposed) An Activator should make available the service description for a knowledge object.

(proposed) Access to the internals of the KO (deployment and payload files) should not be exposed, except that KOs of "resource" type may specify particular payloads for client access under appropriate service paths in the service description.

(proposed) An activator may implement additional operations for the Shelf API to support development or demonstration of KOs. For example, uploading or importing KOs, loading KOs from a manifest file, deleting KOs. See Shelf API for more info.

(proposed) It is especially useful for Activators used in protyping and demonstration to allow a manfifest to be posted to the activator in prder to load KOs at runtime. This should not be enabled by default except in development environments as it representas an vulnberabiltiy.

# List KO resources

GET /kos HTTP/1.1
Accept: application/json

Returns a list of knowledge object resources in a minimal representation.

(proposed) Returns a KO manifest

HTTP/1.1 200
Content-Type: application/json
"@id": "ipp-lowercholesterol",
"@type": "koio:KnowledgeObject",
"@id": "99999-fk4md04x9z",
"@type": "koio:KnowledgeObject",

# Get an individual KO resource

GET /kos/{naan}/{name} HTTP/1.1
Accept: application/json

# Get a versioned individual KO resource

GET /kos/{naan}/{name}/{version} HTTP/1.1
Accept: application/json

Returns a single knowledge object resource in a minimal representation. If a version is supplied that version is returned. If no version is supplied and multiple versions of the object exist in the Activator the current default version for requests is returned (the version will be available in the returned metadata representation). See #Default KO versions for more info.

HTTP/1.1 200
Content-Type: application/json
"@id": "ipp-lowercholesterol",
"@type": "koio:KnowledgeObject",
"@id": "99999-fk4md04x9z",
"@type": "koio:KnowledgeObject",

# Application and Health Information

Activators should provide application and health information via /health and /info endpoints.

# /health (Required)

The health enpoint must provide a { "status": "<UP|DOWN>" } response at a minimum. The/health` endpoint should indicate the status of individual components (adapters, shelf cdo store, runtimes, KOs and their activation status) to aid montioring in troubleshooting Activator deployments.

We suggest following the conventions in the Spring Boot production health information guidelines.

Health information should focus on details that help understand wy the Activator or a component is up or down. Extended information may be made available under an /info endpoint. See /info below.

GET /health HTTP/1.1
Accept: application/json

An UP response returns an overall status and a map of indivdual componet statuses:

HTTP/1.1 200
Content-type: application/json
  "status": "UP",
  "components": {
    "activationService": {
      "status": "UP",
      "details": {
        "kos": 0,
        "endpoints": 0
    "diskSpace": {
      "status": "UP",
      "details": {
        "total": 500068036608,
        "free": 336108306432,
        "threshold": 10485760,
        "exists": true
    "org.kgrid.adapter.javascript.JavascriptAdapter": {
      "status": "UP",
      "details": {
        "type": "JAVASCRIPT",
        "created": "2020-06-18T18:07:52.492425Z"

A DOWN response returns:

HTTP/1.1 503
Content-type: application/json
  "status": "UP",
  "components": {
    "activationService": {
      "status": "UP"
      "org.kgrid.adapter.javascript.JavascriptAdapter": {
      "status": "DOWN"

An Activator implementation may use additional statuses as needed which can be documented for deployers, etc.

# /info (Optional)

Additional or extended information about the opertating characteristics of the Activator can be made available under an /info endpoint. See Spring Boot application health information guidelines for examples of suitable patterns which can be implemented in many different frameworks and languages.

We suggest that implementations provide things like a list of adapters and runtimes currently deployed, as well as counts or lists of KOs available to the Activator, endpoints activated, perhaps total requests, uptime, build information, key environemnt variables, etc.

Be careful not to expose sensitive information. The /health and /info endpoints should be secured (e.g. with OAuth 2.0 Bearer Tokens).

The /info endpoint should return a map of information sets in JSON or YAML.

##Notes If a KO is changed, the activator will have to be restarted to see the changes take effect.

Last Updated: 11/13/2020, 7:42:48 PM