This multi-part series addresses the need for a single semantic data model supporting the Internet of Things (IoT) and the digital transformation of buildings, businesses, and consumers. Such a model must be simple and extensible to enable plug-and-play interoperability and universal adoption across industries.
. In part two we identify existing industry standards and open source approaches to delivering interoperability at the application layer.
Navigate to other parts of the series here:
- Cross-industry semantic interoperability: Glossary
- Cross-industry semantic interoperability, part one
- Cross-industry semantic interoperability, part three: The role of a top-level ontology
- Cross-industry semantic interoperability, part four: The intersection of business and device ontologies
- Cross-industry semantic interoperability, part five: Towards a common data format and API
“The nice thing about standards is that you have so many to choose from; furthermore, if you do not like any of them, you can just wait for next year’s model.” – Andrew Tanenbaum
Community-driven approaches to the metadata challenge
We’ve all become accustomed to a seemingly unending stream of new protocols, initiatives, and alliances, all aiming to usher in the era of ubiquitous sensing and control – the Internet of Things (IoT) we’ve all been waiting for.
By now you’d think we’d have settled on a common connectivity layer for IoT devices, but there are technical factors that have posed quite a challenge to finding a common interoperable solution to connectivity. Tradeoffs among cost, radio range, data rate, and power consumption make it difficult to find a one-size-fits-all answer.
Many “IoT standards” consortia involved in the connectivity layer are heading for the high ground (to the application layer where everything is software and the laws of physics don’t apply). While device interoperability within the application layer is not yet mature, business-to-business (B2B) interoperability within this layer was addressed, albeit imperfectly, over 20 years ago via the Electronic Data Interchange (EDI).
We now see “IoT standards” and “business standards” consortia converging on a center point of interoperability within the application layer. For manageability, this series will focus on the semantic interoperability approaches of nine consortia that collectively:
- Span the connectivity and application layers of the OSI model (Figure 12)
- Address the majority of the use cases of five inter-related industries: Homes & Buildings, Energy, Retail, Healthcare, and Transportation & Logistics (Figure 13)
Figure 12. Consortia interoperability approaches within OSI layers.
Figure 13. Consortia semantic work by industry.
Bluetooth () is a wireless technology standard for exchanging data over short distances that is managed by the Bluetooth Special Interest Group (SIG), which has more than 30,000 member companies. At the consumer level, Bluetooth-enabled devices are the most prevalent example of application-layer interoperability among highly-constrained devices.
When a Bluetooth network is established, one device takes the role of the master while all other devices act as slaves. The basic rate/enhanced data rate (BR/EDR) version, Bluetooth “classic,” is optimized for sending a steady stream of high-quality data (i.e., music) in a power-efficient way. The newer low energy (LE) version, Bluetooth Smart, is more suitable for IoT and, and is built on an entirely new development framework using Generic , or GATT.
- Profiles – For two Bluetooth devices to be interoperable they must support the same profiles. Bluetooth has its own set of application-layer profiles that currently revolve around the familiar “peripheral” roles traditionally fulfilled by Bluetooth classic (i.e., headsets, speakers, mice). Bluetooth Smart supports GATT profiles that expand roles and use cases into personal fitness and Healthcare (e.g., blood pressure, heart rate sensors, thermometer, weight scale). GATT defines a hierarchical data structure that is exposed to connected Bluetooth Smart devices. Each profile describes a use case, roles, and general behaviors based on the GATT functionality.
While there are Bluetooth Smart lighting products on the market today, there is no standardized application-layer protocol to provide multi-vendor interoperability. But Bluetooth Mesh is due out any day now, gunning for the same IoT network use-cases as Thread and Zigbee; with it will surely come an expanded set of GATT profiles beyond peripherals to Home & Building use cases such as lighting, HVAC, etc.
- Assigned Numbers – Bluetooth assigns to various related to provisioning (companies, devices) and semantics (units of measurement, data types).
GS1 () is a global organization that develops and maintains the most widely used supply chain standards system in the world. Over a million user companies execute more than six billion transactions daily in 150 countries using GS1 standards.
GS1 has developed several standards within the application layer that support interoperable exchange of business-critical information, including transactional, product, and visibility event data. These standards primarily address data exchange between trading partners within the Retail, Healthcare, and Transport & Logistics industries.
GS1’s “Global Language of Business” connects the physical and digital worlds, laying the foundation for IoT. By extending its system of standards, GS1 can potentially play a pivotal role in accelerating the pace at which “things” can be efficiently identified, interconnected, and made interoperable to become industry’s global language of businesses, people, and things.
- EPC Information Service (EPCIS), Core Business Vocabulary (CBV) – EPCIS is a GS1 standard, originally based on RFID technology, that enables disparate applications to create and share “visibility event data” about physical or digital objects. Its primary use case has been supply chain traceability, enabling trading partners to share information about the physical movement and status of products as they travel throughout the supply chain. It helps answer the “what, where, when, and why” questions to meet consumer and regulatory demands for accurate and detailed product information. An emerging use case is IoT.
The CBV provides core semantics used to populate EPCIS data schemes to ensure interoperable data exchange, reducing the variation in how different businesses express common intent.
- Global Product Classification (GPC) and SmartSearch – GPC classifies products based on their essential attributes and their relationships to other products. There are GPC standards for everything from camping equipment to footwear, home appliances to toys.
SmartSearch is GS1’s external extension vocabulary to schema.org and is expected to provide significantly richer online product descriptions for use in web search. A challenge remains to reconcile differences between the two vocabularies.
- Global Data Synchronization Network (GDSN) – GDSN is an Internet-based, interoperable network that enables trading partners to synchronize GPC-compliant product data based on a global registry of data stores associated with trading partner relationships.
- EDI – GS1 EDI provides global standards for electronic messaging of business transactions occurring across a supply chain, including order, shipment, and payment objects. GS1 has three sets of complimentary standards: EANCOM, XML, and UN/CEFACT XML.
- Identification Keys – Identification Keys are GS1-structured, globally unique for companies, trade items, locations, containers, and assets. They are used within GS1 barcodes and EPC/RFID and to identify objects within EPCIS events and EDI transactions.
Internet Engineering Task Force (IETF)
IETF () is a global community of network designers, operators, vendors, and researchers concerned with the smooth operation and architectural evolution of the Internet. IETF’s Request for Comments (RFC) document series contains technical and organizational notes about the Internet and includes protocols, procedures, and concepts.
- Extensible Provisioning Protocol (EPP) – EPP (RFC 5730-RFC 5734) is an application-layer, client-server protocol for the provisioning and management of objects stored in a shared central repository. Specified in XML, the protocol defines generic object management operations and an extensible framework that maps protocol operations to objects.
The EPP protocol suite currently contains a base protocol specification and semantics for Internet domain and host object classes, and “contact” identifiers associated with persons and organizations. EPP was initially developed to enable Internet registrars that sell online identity services to access central domain name registry data more efficiently. Specifications for other object classes may be developed as needs are identified.
The Internet Architecture Board (IAB) provides architectural oversight for IETF. In 2016, IAB organized an IoT Semantic Interoperability (IOTSI) Workshop to assess gaps in current metadata models.
Object Management Group (OMG)
OMG () focuses on modeling and model-based standards that enable software interoperability. OMG manages the Industrial Internet Consortium (IIC) and developed the Data Distribution Service (DDS) that is a “core connectivity standard” within IIC’s Connectivity Framework. OMG also manages the Unified Modeling Language (UML) for modeling applications, business processes, and data structures.
OMG’s Healthcare Domain Task Force is developing a suite of healthcare interoperability standards in concert with Health Level Seven (HL7) that provide a model-driven platform supporting legacy interface protocols while aligning with current industry best practices.
In 2017, OMG assumed ownership and management of the technology standards (ARTS) of the National Retail Federation and created a new ARTS Retail Domain Task Force. The standards include the ARTS data model, UnifiedPOS, POSlog, A2A messaging, and BPM.
- ARTS Operational Data Model (ODM) – ARTS ODM is a relational data model that incorporates hundreds of transactional and master data object classes supporting retail business operations.
- UnifiedPOS (UPOS) – UPOS is a globally adopted interoperability standard that includes UML-defined data models for over 30 point of sale (POS) peripheral device classes (e.g., cash drawer, receipt printer, etc.). These data models are interoperable within UPOS control and service layers.
Open Connectivity Foundation (OCF)
OCF () has become one of the largest industrial connectivity and interoperability standards organizations for IoT devices, with more than 300 member companies. OCF was formed by the merger of the Open Interconnect Consortium (OIC) and the AllSeen Alliance in 2016. Prior to the merger, OIC acquired the assets of the UPnP Forum, which developed the UPnP Management and Control Specifications.
The OCF Specification addresses the same interoperability layers as Zigbee Dotdot, and includes a generic resource and security model with RESTful interactions. IoTivity is an open-source reference implementation for the OCF specifications.
- Models – OCF’s peer-to-peer (P2P) RESTful architecture is based on Create, Read, Update, Delete, Notify (CRUDN) operations that securely communicates using simple, open data structures (models) that describe basic resources and the devices that are composed of these resources. oneIoTa is an open tool for developing and managing the models of OCF and other organizations as well as the mappings between them. While OCF has developed its own models for device classes supporting Home and Building use cases, it is working in liaison with the Personal Connected Health Alliance (PCHA) for Healthcare and EEBus for Energy.
Project Haystack () is an open-source community addressing the challenges of data modeling for building and IoT within the application layer. It has developed a data modeling methodology, tagging libraries (taxonomies), a REST communication protocol, and reference implementations.
Project-Haystack’s vision is to streamline the use of data from the IoT by creating a standardized approach to defining “data semantics” and related services and API’s to consume and share the data and its semantic.
- Tags – Project Haystack incorporates a simple, flexible tagging approach that can be used in media from Excel spreadsheets and CSV text files to data tables in embedded devices, XML representations, web services, and others.
was launched by search engine operators in 2011 to create and manage a common set of semantic schemas for structured data markup on web pages. The markup enables search engines to search and aggregate web content by defined entities, their , and relationships.
- Ontology – ’s ontology was initially developed for common web content based on top-level . Increasing emphasis is placed on ontology extensions created through a broad network of community collaborations. Unlike hosted extensions (e.g., bib.schema.org, auto.schema.org, etc.) that are reviewed, versioned, and published as part of schema.org itself, external extensions to schema.org (e.g., gs1.org/voc/for rich product descriptions) are fully independent and have their own workflows, review processes, and infrastructure.
A proposed hosted extension is intended to merge IoT and non-IoT semantic vocabularies within a sustainable and extensible ontology that forces the decoupling of IoT data structures from the tools, products, and applications that use the data.
The Open Group
The Open Group () manages The Open Group Architecture Framework (TOGAF) standard for enterprise architecture frameworks and provides forums for its 500-plus member organizations to facilitate enterprise integration based on open standards and global interoperability.
The Open Group Healthcare Forum seeks to advance interoperability to exchange key health and healthcare data. The Open Platform 3.0 Forum is developing an interoperability standard for digital platforms, considering the convergence of mobility, analytics, cloud computing, and IoT.
- Open Data Element Framework (O-DEF) – The O-DEF is an overarching semantics framework that can accommodate industry-specific semantic standards as “plug-ins.” Its “core index” comprises top-level , properties ( ), and . Plug-ins developed by the Open Group and other organizations can extend the “core index” to support specific use cases and industries.
- Open Data Framework (O-DF) – O-DF is an Open Group IoT standard that supports interoperable data exchange. Object make it possible to link the data about a single thing that may be located in different information systems.
Zigbee () has long been associated with its 2.4 GHz IEEE 802.15.4-based network stack, now called “Zigbee PRO.” The technology defined by the ZigBee specification is intended to be simpler and less expensive than other wireless personal area networks (WPANs) such as Bluetooth or Wi-Fi. In 2013, “Zigbee IP” based on 6LoWPAN was added that targets the smart grid market. There’s also “Zigbee RF4CE,” which provides radio frequency control for consumer environments. Zigbee has over 400 member companies and over 1,300 certified products using its technology.
- Cluster Library – The Zigbee Cluster Library (ZCL) defines and catalogs how a large collection of will interoperate and represents over 10 years of collaborative work. This catalog provides a fine-grained breakdown of covers a broad range of device classes (e.g., HVAC, lighting, etc.) and industries (e.g., Homes & Buildings, Retail, Healthcare, Energy, etc.).
- Dotdot – The Zigbee Alliance recently announced a new “Universal Language for the IoT” named Dotdot to decouple the ZCL standards specification from the connectivity layer. The ZCL legacy of Dotdot gives Zigbee a substantial head start in defining objects and actions within the application layer.
The separation of these application-layer definitions from the networking and physical-layer connectivity is significant. Prior to this, having a “Zigbee Certified Product” meant that it complied at the application layer and at the Zigbee network and physical layers. Now, there is the possibility of having Dotdot-compliant devices that are compatible at the application layer but with differing physical layers.
Zigbee has begun to demonstrate Dotdot’s interoperability across different connectivity stacks (as shown in Figure 14), with an initial demonstration of Thread-based devices using Dotdot at CES 2017. Conceivably, then, a consumer could have Thread devices interoperating with Zigbee devices at the application layer, even though they don’t use the same connectivity technology. In practice, achieving this would require some sort of gateway device(s) at the TCP/IP level to adapt Dotdot to each connectivity layer being used. This pattern of “protocol convergence at the TCP/IP level” is a common theme of application layers.
An interesting consequence of separating the application layer interoperability from the connectivity layer is “logo confusion.” For example, a smart lighting product would need two certifications: one for “Thread Certified Component” and another for “Dotdot.” If we expect a light switch to communicate directly with a light fixture, we’d have to look for both logos to match. It remains to be seen whether or not this “dual logo” situation will confound the market.
Figure 14. Consortia move toward interchangeable connectivity layers.
Part three discusses the role of an ontology in addressing the metadata challenge.
For term definitions, see .
6. Ewing, David. “Delving deeper into Dotdot – Zigbee’s new ‘Universal Language for the IoT’”, Embedded.com, April 2016.