There is a substantial spectrum of economic activities that depend on reacting to events. Event-reaction systems require event descriptions to be interpretable and reliable as to the source and integrity of their contents. Enterprises guarantee all those conditions by insuring event data sources, destinations, and data flows between them all occur within a common secure (enterprise-wide) realm.

(Fig. 1. Pub-Sub with standard notifications)

Standard definitions apply:

• Publisher: Application or service that collects and sends data messages about specific event types irrespective of who consumes those messages,

• Broker: Receives messages from publishers, validates them and routes them to subscribers based on agreed rules. It can also queue, prioritize, and store messages for guaranteed delivery,

• Subscriber: Application or service that registers its interest in specific event types with the broker

Event-reaction systems where publishers, broker, and subscribers do not share a common trusted realm, or notifications propagate through insecure media (packet data services: GPRS, Internet, etc.), face limited design options.

Description:

The aim of this work is to describe a publisher-broker-subscriber service that can be used to implement event-reaction systems that do not share a common trusted realm. Event notification messages (hereafter referred as Actionable Notifications, or AN) are sent by publishers to a broker, validated and subsequently relayed to subscribers. As received by a subscriber, the AN must remain interpretable, authenticated (have a known publisher), and the subscriber should be able to verify its content has not been altered in transit.

(Fig. 2. Pub-Sub with actionable notifications)

Operation:

• Interpretability of AN works because the broker validates notifications adhere to public XML schemas agreed by publishers,

• Authentication and message integrity are guaranteed by cryptographic signature of the content provider,

• Confidentiality between publishers and brokers, or between brokers and subscribers may be added by leveraging cryptographic technology (PKI, signatures)

Feasibility:

There are many message-broker software systems in use (some even Open Source) onto which event-types, XML schemas, validation, and essential cryptographic functions may be added.

This service may be seen as infrastructure, and cover a wide range of event types, allow for standard interfaces between brokers and subscribers, and extend over large geographical distances. Event-reaction systems that become possible may find applications in AI, Robotics, wide-area data collection and automation in agriculture, law enforcement, health industry, transport networks, tactical situational awareness, etc.

Future:

Brokers may add further value by:

• Creating a catalog of content types with publishers and XML schemas, options for subscribing, APIs, tracking publishers traits of interests to subscribers: reliability, timing, standards compliance, etc.

• Helping publishers evolve their XML schemas and service traits, to stay competitive in the AN market,

• Facilitating monetization of AN to large sets of publishers, which results in new business models and applications,

• Enforcing publisher requirements to control which subscribers have access to which event types,

• Implementing post-quantum cryptography standards mandated by the NIST, high throughput and availability measures, corresponding to infrastructure-level design