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This document describes the message structure and implementation information for ERCOT's External Web Services (EWS). This interface has been developed for Market Participant applications that need to interact with ERCOT Nodal Market systems. The intended audience of this document is developers that will be integrating Market Participant applications to the ERCOT Nodal systems through the use of the interfaces described within this specification.

This documentation provides a general introduction to the services, specific details regarding the message structure, and the overall security implementation. This is followed by sections that are specific to each service support by EWS. Additionally there are sections regarding Notification listeners. The appendices provide XML Schemas, WSDLs and additional examples.

The interfaces and related interactions described by this document define the externally-visible (black box view) perspective of the services provided by this project. It is the intent of this specification and interface architecture to shield Market Participants from the details of systems integration internal to ERCOT.


The interfaces described by this document are intended to be used by Market Participants for machine to machine integration. This document is intended to provide all the details of the message structures and technical interoperability standards required for the machine to machine interface.


The scope of this document is to describe web services provided for integration by Market Participants from the perspective of external integration. This document has program level scope as related to web services that would be used by Market Participants for machine to machine interaction with nodal applications as detailed in an agreed list of interfaces to be managed by the Nodal project. The intent of this design is to leverage the integration layer (IL) to expose web services needed for external integration by Market Participants.

The following are specifically outside the scope of this document:

  • The details of integration from the IL to internal ERCOT applications are outside the scope of this specification

  • Inter Control Center Communications Protocol (ICCP) communications

  • Interactions with application User Interfaces (UI)

  • Access of information through

  • Usage of the Public API for historical public content. Public API documentation is available at ...

Definitions, Acronyms, and Abbreviations

Term/Acronym Definition
ADJ Adjustment
AS Ancillary Services, includes spinning reserve, non-spinning reserve, responsive reserve and regulation
award An award identifies the acceptance of a bid or offer.
BidSet A BidSet is an XML container type for a collection of bids, offers, trades and schedules as defined by the IEC Common Information Model
CIM Common Information Model, an IEC standard
CRR Congestion Revenue Rights, a system implemented at ERCOT
CSV A file format that uses values separated by commas
DAM Day Ahead Market
DRUC Day-Ahead Reliability Unit Commitment
EMS Energy Management System, a system implemented at ERCOT
FIP Fuel Index Price
FOP Fuel Oil Price
FTP File Transfer Protocol
GUID Globally Unique Identifier. GUIDs are usually implemented as random 128 bit numbers that are usually represented as a string of hexadecimal digits.
HASL High ancillary services limit
HDL High dispatch limit
HEL High emergency limit
HRUC Hour-Ahead Reliability Unit Commitment
HSL High sustained limit
IEC International Electrotechnical Commission
LASL Low ancillary services limit
LDL Low dispatch limit
LEL Low emergency limit
LMP Location marginal price
LSL Low sustained limit
MCPC Market clearing price for capacity
MIS Market Information System, an umbrella for the various interfaces provided to Market Participants by ERCOT
MMS Market Management System, a system implemented at ERCOT
MP Market Participant
MW Megawatt, a measure of power
MWh Megawatt hour, a measure of energy
NMMS Network Model Management System, a system implemented at ERCOT
NOMCR Network operating model change request
Non-Spin Non-spinning reserve
OASIS Organization for the Advancement of Structured Information Systems
Operating Date Synonymous with Trade Date
PMCR Planning Model Change Request
POC Proof Of Concept
QSE Qualified Scheduling Entity. This is a type of Market Participant. Each QSE is identified by a certificate. A QSE is identified by a DUNS number, 'long name' and 'short name'
RDF Resource Descriptor format. An XML format used by NMMS for model exchanges using IEC 61970-501.
Reg-Down Regulation down
Reg-Up Regulation up
RRS Responsive reserve service
RTM Real-Time Market
SAMR Special Action Model Request
sink Sink settlement point
SOAP Simple Object Access Protocol
SoSA System of Systems Architecture
source Within a bid, offer, schedule, trade or award this refers to the source settlement point. Within a message header, this refers to the ID of the market participant.
SP Settlement Point
SPP Settlement Point Price
TP Transmission Provider
Trading Date Synonymous with Operating Date. Represented in XML using the 'tradingDate' tag. This is based on Texas prevailing time.
UTC Universal Coordinated Time, an international standard
WS Web Services. There are many web service standards that are commonly prefixed by 'WS'.
WSDL Web Services Definition Language
XML eXtensible Markup Language
XSD XML Schema, used to define the structure of XML documents
XSL XML StyleSheet Language
Z Zulu, an indicator for the use of GMT or UTC time


Artifact Definition
External Interfaces Conceptual Design Conceptual design for external interfaces using web services
External Interfaces Security Design Specification Detailed security design for external interfaces. This is a companion document to the External Interfaces Conceptual design.
OASIS WS-Notifications OASIS Web Services Base Notification standard
OASIS WS-Security OASIS Web Services Security
XSDs Specific message structure and element details.

Additional references to related standards are described in section 1.6.

Program-level Standards

In general, the design described by this document will leverage web services and related security standards as defined by the World-Wide Web Consortium (W3C) and OASIS. Program-level standards include those related to security, as well as basic web service standards including:

  • XML

  • XML Schema

  • XPath

  • XSL

  • SOAP

  • Web Services

  • WSDL

  • RDF

These are described in the companion security design document. W3C standards can be freely accessed from

Another key program standard is the IEC Common Information Model (CIM), as defined by IEC 61970-301. This is used to define models used by ERCOT, which are exchanged using IEC 61970-501. It will also be leveraged by this design for the definition of messages used for interfaces. There is also a standard for message structures defined by IEC 61968-1. There standards can be purchased from the IEC web site at Materials related to IEC standards, including the CIM model it self can be freely obtained from the UCA International Users Group SharePoint at

There are several key Internet Engineering Task Force references. These include:

  • Internet Engineering Task Force RFC 2828: Internet Security Glossary

  • Internet Engineering Task Force RFC 2119: Key words to indicate RFC requirement levels

  • Internet Engineering Task Force RFC 2246: Transport Layer Security (TLS)

  • Internet Engineering Task Force RFC 3275: XML Digital Signature and Processing

IETF documents can be freely obtained from

An ERCOT variation of the OASIS WS-Base Notification standard is used to define the mechanism for issuance of asynchronous notification messages to Market Participants. Given the application of WS-Notifications for Nodal, only a subset of the capabilities of WS-Notifications is required. OASIS standards being leveraged include:

  • Web Services Notifications (WS-Notifications)

  • Web Services Security (WS-Security)

  • Web Services Security X.509 Token Profile

  • Web Services Security Username Token Profile

OASIS standards can be freely obtained from

The definition of timestamps is specified by ISO-8601, with the exception that timestamps of 24:00:00 are not used for compatibility reasons. This is partly a consequence of the XML Schema definition for 'dateTime', where hour 24 is not explicitly allowed. There are some implementations of timestamps within software products that do not correctly handle timestamps of 24:00:00.

ISO standards can be purchased online from a variety of sources including ANSI, at Descriptions of ISO-8601 can be freely obtained from other sources including Wikipedia