Article #108 - Functional Levels of Communication and Control Technologies
As this KnowledgeBase matures, one objective may be to classify standards with respect to the functional level(s) which they encompass. This will facilitate comparing efforts across industry sectors.
Table 1: Functional Levels Surrounding Communication and Control Technologies below details five different functional levels of technologies and standards that are relevant to GridWise™. It presents examples and sub-layers of the various levels, and some comments to better explain the different levels. These five layers are summarized in the figure below.
This schematic of functional levels surrounding communication and control technologies can help us understand and differentiate various standards related to GridWise. Some explanations of each level are provided below, to position each area in context historically and with respect to GridWise in a general sense. Transverse issues have not yet been addressed; these are domains that may affect several levels and are often treated separately by technical specialists and standards-making groups (interoperability, security, quality of service, conformance, etc.).
The data transfer/transport functional level can be equated to the functions encompassed in the Open Systems Interconnection (OSI) seven-layer model of network infrastructures (though some interpretations may put the top, application layer in one of the higher functional levels suggested here)[1]. Standards and technologies are quite mature in this layer, with relatively well established technologies (like TCP/IP and corresponding physical network media). New efforts are generally focusing on extending capacity (kilobits per second) for supporting applications such as home entertainment, or on reinforcing security and reliability (for example, the next generation of Internet Protocol, IPv6).
The data exchange level includes both transferring operational data and transferring business data. The contextual differences surrounding operational and business data result in different requirements (timeliness, authentication, volumes...). Specific standards exist now for electronic data interchange (EDI), and typically data exchange standards for operational data relies on domain specific standards. The convergence of many standards surrounding data integration, semantics, and syntax demonstrates the maturity of technologies and standards at this level. A large part of new standards in this level are extensions and new instances of existing data models and mappings.
Table 1. Functional Levels Surrounding Communication and Control Technologies
| Levels | Examples | Sub-layers | Comments |
|---|---|---|---|
| STRATEGIC KNOWLEDGE Data and information re-use across companies. | Collaboration | Multi-function, multi-company. |
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| KNOWLEDGE Data re-use for enterprise-wide planning, decision-making. | Integration | Multi-function, one 'roof' (company) |
|
DATA USE In context, data content is information, intelligent systems may be applied:
|
Business Processes (using intelligent business information) |
|
|
| Operational Processes (using intelligent operational information) |
|
|
|
| DATA EXCHANGE Content of transferred elements are structured, codified, mapped, integrated into another system.(Front-end/Back-end Integration) | EDI / e-EDI(transferring intelligent business information, System A to System B) |
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EDI implies data transfer between two separate companies.(Mapping, translating, middleware, links, APIs) |
| Data / e-Data (transferring intelligent operational information, System A or Component A to System B or Component B) |
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Data exchange (sometimes also called EDI) not necessarily involving separate companies.(Mapping, translating, middleware, links, APIs) | |
| DATA TRANSFER / TRANSPORT Bits and bytes are transferred from point A to point B. (Messaging) |
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(Comm. Protocols)
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Content and context independent (though different domains have different requirements for speed, reliability, security, and different physical contexts). |
Technologies at the data use level take the function one step higher, using exchanged data to complete transactions or to enable control systems. Not only is data collected, transported and exchanged, it is also used by an application to make decisions and cause reactions. This level is less mature than the lower two levels - a plethora of different standards for different needs and different domains exemplify this immaturity. This is currently among the most active and evolving levels, as growing markets drive new implementations and standardization. Standards convergence efforts (such as NIST's eBusiness Standards Convergence, eBSC) are starting to progress for data use functions.
Both the knowledge level (integrating data use) and the strategic knowledge level (integrating data use across diverse entities for mutual collaboration) are market driven. These functions are typically addressed through unique implementations or proprietary systems, in some case with propriety standards or those maintained by a trade group. To enable functions at these levels, some high-level standards and research are addressing relevant issues such as semantic integration and knowledge management. In the GridWise context, the strategic knowledge level might encompass areas surrounding wide area monitoring, planning, and control. The knowledge level might encompass integration of EMS (energy management system), DMS (distribution management system) and ERP (enterprise resource planning) type systems.
Using Functional Levels to Understand and Compare Standards
These functional levels can help with landscaping the vast world of communication and control standards. The first example below considers standards from different sectors that are focused on the same level. The second example considers standards within one sector and categorizes them according to the different functional levels they address.Examining standards from different sectors but focused on the same level allows us to examine a sub-group of related standards and identify similarities and differences in these various standards. For example, one might examine the OPC Data Access (DA) and XML DA (eXtended Markup Language Data Access) specifications and identify other standards currently in use in the electric power and building systems sectors that perform similar functions and how they compare methodologically to OPC DA or OPC XML DA.
Answering these sorts of questions will enable better characterization and appreciation of the roles and strengths of key standards. For example, gaining insight into the sources of differences, whether from different objectives, different environments (requirements like speed, reliability, security...), different approaches to control paradigms, different approaches to communication, backward compatibility requirements (e.g., legacy systems), or advancing generations (e.g., integrating XML or not). Gaining this knowledge will facilitate steps toward interoperability and convergence.
Examining standards within one sector with respect to the functional levels they address can help to clarify the roles played by these standards, with an objective of clarifying the roles of various standards, their similarities, complementarities, differences in context, and differences in technical approaches. For example, in the home networking sector, OSGi, UPnP, EIA/CEA 709 (LonWorks) and EIA/CEA 600 CEBus Standard, and EIA/CEA 721 Generic Common Application Language each fulfill different functions with some overlaps. Identifying the differences, overlaps, and points of convergence between these various standards within one sector can help to categorize and characterize the realm of standards.
[1] It is assumed readers are familiar with the ISO's Open Systems Interconnection (OSI) Architecture. Numerous works present this models, including Zimmerman 1980.