1) Workflow automation components
The Arrowhead local cloud is running on the Edge Gateway, providing capabilities to the Field abstraction component and the Automation workflow management component. It consists of all prerequisite components for Service Oriented applications to run on the edge tier.
It is expected that individual installations would have customized local clouds according to requirement. With services and systems only operating when required. Full authorization security is supported at the edge automation layer, meaning that Far-Edge edge gateway is protected by the Arrowhead security mechanisms.
The Workflow Manager is a SOA-based system developed for the Far-Edge platform and operating within the Arrowhead local cloud paradigm. It is a form of a bookkeeper that is responsible for managing the progress of the production process/recipe and reporting back to the Factory Control System.
The Far-Edge Ledger client will wrap the ledger client libraries and provide the smart service contracts as SOA-based interfaces. These services are what is used by the rest of the EAS. In this way, EAS are able to independently interact with Smart Service Contracts. It is possible that more than one Ledger Client System, or perhaps multiple versions of the Ledger Client System co-exist within a single Edge Gateway instance. This will allow for gradual change as new Smart Contract Services are added, removed or changed.
The Arrowhead Plant Description system is responsible for maintaining a functional and topological map of the systems available in the local cloud. This means that the plant description has knowledge regarding the edge nodes connected to the edge gateway. It is kept up to date through the Arrowhead Device and System Registries operating within the Field Abstraction component. The information stored in the plant description is used for engineering the edge tier gateway and nodes.
The edge automation services are operating above the field abstraction.
2) Ledger Tier Integration
Integration of EAS with the Ledger Tier happens in three places:
- A use-case-specific Ledger Service that runs on the Distributed Ledger infrastructure and implements a number of network service endpoints, by means of which:
- receives a working copy of each new master Production Order that is issued by factory systems;
- stores and manages the working copy on the Distributed Ledger, so that it’s shared with all EAS instances;
- enforces access and business rules of read/write operations on the working copy, acting on behalf of the owner of the master;
- Notifies the owner of the master (typically a MES) of each successful write operation done on the working copy, so that the master can be updated in the background.
- A Ledger Client software library that implements an in-process version of the Ledger Service interface, hiding most of the complexities of interacting with a permissioned Blockchain infrastructure.
- The Workflow Manager software embeds the Ledger Client library and tunnels all calls to the Ledger Tier through it.