Industrial Internet: Towards Interoperability and Composability
through their APIs. If we consider a CPS, or an Industrial Internet system, as a collection of
capabilities, albeit supported by physical components, the SOA paradigm seems to apply and may
be beneficial to the Industrial Internet. Within this paradigm, the interoperability task would be
to provide the common meta-models and agreed interfaces about specific services. However, in
the Industrial Internet, the meta-models and interfaces are not static but expected to change
dynamically. A temporal challenge in interoperability thus emerges: how to dynamically maintain
the required level of interoperability beyond the time of initial deployment as existing services,
including those embedded in the CPSs, independently evolve through their respective lifecycles
(e.g., upgrading), and as new services/CPSs are joining the system. Therefore, the traditional SOA
approach of statically composing capabilities is inadequate for the Industrial Internet for it leads
to a brittle system nonresponsive to changes in its constituents or its environment.
If we consider that the services in the SOA paradigm are expressed by their respective APIs, then
the question becomes how to ensure, automatically where possible, interoperability and
composability as the API evolves over time. To address this class of issues, some forward-looking
and innovative approaches are being actively discussed within the Industrial Internet Consortium
(IIC). One bold approach 33 is to define various levels of API maturity with the highest level
providing a mechanism:
1. to establish an a priori service contract between the interacting parties upon which an
active service contract can be adapted to changing conditions upon mutual agreement
between the parties,
2. to share service metadata about the service, potentially including a description of the
meta model, precondition/constraints, expectant behavior,
3. to describe the service API providing the capability, and
4. a meta-service API for notifying service changes, updating the service metadata and
negotiating adjustments to the service contact to adapt to changes in the service or usage
condition.
This approach may provide a powerful mean to address not only the quantitative and qualitative
but also the temporal interoperability challenges presented in the Industrial Internet.
4.
INTEROPERABILITY EVALUATION BASED ON THE INDUSTRIAL INTERNET
REFERENCE ARCHITECTURE
To meet the unique quantitative, qualitative and temporal interoperability challenges in the
Industrial Internet, a systematic approach is needed. The starting point is to establish shared
architectures and models for the Industrial Internet. Without a common architecture model, we
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