The data exchange specified by TROLIE implies that the Ratings Provider and the Transmission Provider must both agree on identifiers for Transmission Facilities and Network Segments. This is required for the exchange to function.

IEC CIM standards document IEC 61970-452 defines the concept of a master resource identifier (mRID), issued by a model authority. In theory, mRIDs may be used for globally consistent identification of any network model object, which would provide a shared identifier that these parties could agree on. In Europe, this would be feasible, as CIM data exchange has become commonplace in response to the ENTSO-E-mandated Common Grid Model Exchange Standard (CGMES).

There is no such prevailing standard in North America, and CIM adoption has been limited, so we cannot assume common mRIDs across systems. While mRIDs are of course supported in many software products, they are not necessarily used or shared widely in data exchanges.

Therefore, while mRIDs provide architectural simplicity to TROLIE, we do not believe that they can be mandated in order to use TROLIE. In order to integrate systems by the FERC 881 deadline, TROLIE implementations will have to adapt to the names that the various parties actually know and use. This ADR specifies rules and design philosophy on usage of names in TROLIE server and client implementations.


The following list is a summary of rules for TROLIE implementations. Further discussion follows:

  • The server defines which names will be used in a given exchange. The set(s) of names to use are assumed to be pre-coordinated.
  • Clients must conform, in query parameters and request bodies, to the names expected by the server.
  • TROLIE is compatible with CIM mRIDs, and mRIDs are encouraged, but not required.
  • Implementations are free to provide extensions that enhance the behavior, as long as they do not break TROLIE compatibility. For example, GET Operations in TROLIE might be defined that allow the server to return a complete list of names that it knows for a given object.

The TROLIE Server Determines the Names Used

Since the server must process the request, TROLIE servers must generally have an internal representation of the network model they’re operating against. While servers may adapt the names they present to clients in a variety of ways, leaving this decision to the server allows the simplest possible server designs, where the server only knows a single identity for each object. We believe this is a simpler path to interop than attempting to specify a richer name/identity negotiation as part of the specification.

CIM MRIDs are Encouraged

Implementers of TROLIE servers are encouraged to support CIM mRIDs. The benefits to functions of the CGMES such as cross-TSO schedule exchanges are obvious. TROLIE and other such exchanges will benefit from consistent use of these identifiers over time.

Use of CIM NameTypes

In CIM, “mRID” is a property of IdentifiedObject, the base class of most types in the CIM model. IdentifiedObject also provides some additional fields that provide additional identifying information, including:

  • name is intended to be a human-readable identifier.

  • aliasName is a single alternative name. However, it is deprecated in favor of

  • a child collection of Name objects, which can map to a NameType. This construct allows for an extensible set of name types, which could map to arbitrary names in underlying systems owned by Transmission Provider, such as the EMS, planning, asset registration, or names from neighboring authorities.

It is possible that TROLIE server implementations will know about alternative names for various objects. Consider a server-to-server communication where both servers have an mRID from different naming authorities. These parties might pre-coordinate the use of both mRIDs in the Name collection to avoid any ambiguity. To take another example, consider a TO with their own unique name for a transformer while the TP uses an mRID. Assuming the TP also has the TO’s name mapped, then the TP could accept proposals that use just the TO’s proprietary name for the transformer, while including both names in snapshots.


While deferring some challenges to implementors, the intent of this ADR is to aid interop and specification conformance by assigning responsibility for names purely to the server. The tradeoff is that it may require implementors to create extensions and other mechanisms to handle disparate naming knowledge between Transmission Providers and Rating Providers.

This decision also implies rules for TROLIE specification design. Specifically:

  • The server may provide alternative names, based on the CIM Name/NameType paradigm, but only in GETs. The client must never be required to provide them.

  • These headers are represented in an alternative-identifiers attribute of the power system resource list in the header.

These changes are reflected in the current example of In-use forecasts.