Introduction
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.
Purpose
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.
Scope
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:
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The details of integration from the IL to internal ERCOT applications are outside the scope of this specification
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Inter Control Center Communications Protocol (ICCP) communications
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Interactions with application User Interfaces (UI)
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Access of information through ercot.com
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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 |
References
| 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:
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XML
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XML Schema
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XPath
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XSL
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SOAP
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Web Services
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WSDL
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RDF
These are described in the companion security design document. W3C standards can be freely accessed from http://www.w3.org.
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 http://www.iec.ch. Materials related to IEC standards, including the CIM model it self can be freely obtained from the UCA International Users Group SharePoint at http://sharepoint.ucausers.group.org/CIM.
There are several key Internet Engineering Task Force references. These include:
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Internet Engineering Task Force RFC 2828: Internet Security Glossary
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Internet Engineering Task Force RFC 2119: Key words to indicate RFC requirement levels
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Internet Engineering Task Force RFC 2246: Transport Layer Security (TLS)
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Internet Engineering Task Force RFC 3275: XML Digital Signature and Processing
IETF documents can be freely obtained from http://www.ietf.org.
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:
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Web Services Notifications (WS-Notifications)
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Web Services Security (WS-Security)
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Web Services Security X.509 Token Profile
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Web Services Security Username Token Profile
OASIS standards can be freely obtained from http://www.oasis-open.org.
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 http://www.ansi.org. Descriptions of ISO-8601 can be freely obtained from other sources including Wikipedia