Moving on with Overlays Capture Architecture 2.0: A New Era of Semantic Interoperability
The Overlays Capture Architecture (OCA) is a foundation for Dynamic Data Economy structuring and presenting data in a traceable and verifiable way. Recognising today’s need of interoperability between standards, the release of OCA v2, the architecture takes a major leap forward, introducing a modular and extensible approach in the definition of overlays.
Community 2.0
The new specification centers around making overlays easier to define, share, and validate — even by non-technical users. At its core, OCA v2 introduces the concept of Community Overlays, empowering ecosystems to create and maintain their own overlay definitions without deep technical barriers.
We used the term Community (i.e. not ecosystem) to stress the need of creating the flexibility to create specific overlays for a given purposes shared by multiple users. For example, in science this approach helps to define the ultra-precise meaning of certain datasets while keeping them in line with common standards. In compliance, the approach enables the definition of data structures that must match specific regulatory constraints in a given jurisdiction. In supply-chain, the approach enables domain specific definitions of data exchanges to be used across the entire chain without requiring a centralised authority.
Definition of Community-Driven Overlay
Enabling Community Overlays required a different approach to the way the overlays are defined. Instead of specifying them in the OCA specification, we created a Domain-Specific Language (DSL), which allows us to create overlay definitions, which we called OVERLAYFILE.
OVERLAYFILE is a text-based file which can consist of one or many definitions of various overlays. If you are familiar with programming, think of it as a *.h (header) file from C++. If you are not familiar with technology, think of it as the exact structure of the dataset your boss, team, department or company validated for use.
Having clearly defined overlays, the relevant tooling support any community-defined overlay and simplify the way we manage overlays in the whole ecosystem. When you use it, you have the cryptographic assurance to use what the community has validated for use.
A new file type, .overlaysfile, allows communities to formally define their own overlays. By separating overlay definitions from usage, ecosystems can establish governance and enable cross-project reusability. Overlay repositories further support this, enabling easy distribution and import of overlays.
Enhanced Modularity and Validation
The new approach allows overlays to define schemas, ensuring proper structure and data integrity. Tooling can now validate authored overlays against community-defined schemas, reducing errors and increasing trust.
OCA Bundle in JSON format
An OCA Bundle is a set of OCA objects serving as envelop for distribution and usage of the semantic. With v2 we finally introduced long waiting new encoding format which replace old .zip file by simple JSON object. This new format was in test since quite some time in reference implementation of OCA and now it is official part of the OCA specification allowing to simplify the tooling and the way how the bundle is transmitted.
OCA Specification v2
Finally we release RC1 of Overlays Capture Architecture Specification v2.0.0 which is signal for readiness of mentioned features and functions. The process of implementation already started in our reference implementation which can be followed at oca-rs.
Below you would find the list of major changes which version 2.0.0 brings:
Sensitive overlay replaces PII's flagging in capture base. This enables an enhanced approach to privacy and other risks flagged directly in the schema
Categories from the Label overlay have move to presentation layer. Thus strictly enforcing the distinction between data inner structure and meaning with data presentation.
Upgrade to “Community Overlays” of certain previously “core overlays”. - all overlays listed below are nominated as community overlays and hosted in an Overlays Repository.
Information
Transoformation
Presentation
Layout
Conditional
Unit mapping
Introduce SemVer for all objects
Support for 639-1 and 639-3
Support for namespacing in overlay name
OCA2.0 build for stronger, verifiable data integrity
All objects of the Overlays Capture Architecture, the Capture Base, Overlays and Bundle are compatible with CESR encoding. This ensures that those objects can be authenticated using DKMS a KERI based decentralised key management.
This is pivotal to establish cryptographically verifiable integrity of data objects. This property enables the implementation of distributed governance models - a topic that will receive much attention at the Human Colossus Foundation
Webinar at DSWG
The Technology Council, who is responsible for maintaining the OCA specification and reference implementation, hosted a webinar during the Decentralised Semantic Working Group where they delved into the details of the design of the new architecture and all the features of version 2.0.
Looking Ahead
With OCA v2, the Overlays Capture Architecture moves closer to its vision of an open, extensible semantic ecosystem where organizations and communities can seamlessly create, validate, and share schemas.
