Webservices Update for Nodal Market Trials NATF Feb 19, 2010 http://nodal.ercot.com 1

Antitrust Admonition ANTITRUST ADMONITION ERCOT strictly prohibits Market Participants and their employees who are participating in ERCOT activities from using their participation in ERCOT activities as a forum for engaging in practices or communications that violate the antitrust laws. The ERCOT Board has approved guidelines for members of ERCOT Committees, Subcommittees and Working Groups to be reviewed and followed by each Market Participant attending ERCOT meetings. If you have not received a copy of these Guidelines, copies are available at the Client Relations desk. Please remember your ongoing obligation to comply with all applicable laws, including the antitrust laws. DISCLAIMER All presentations and materials submitted by Market Participants or any other Entity to ERCOT staff for this meeting are received and posted with the acknowledgement that the information will be considered public in accordance with the ERCOT Websites Content Management Operating Procedure. http://nodal.ercot.com 2

Today’s Objective Today’s Objective Recap on the EIS changes that are forthcoming and target timeline for implementation Open forum to address any questions / concerns Adjourn http://nodal.ercot.com 3

Schedule for consideration of changes Planned timeline for changes to EIS Specifications 1.19j Feb 2nd - NATF High-Level Overview of planned webservice changes Feb 15th - Release EIS 1.19j Specifications (redlined) & planned release timelines New External Interface Specification 1.19j and Associated XSDs Available to the Market Participants Planned delivery timeline for Market Trials Phase 4 and 5 delivery Feb 19th - Special NATF meeting to review changes to specifications Phase 4 / Late-March 2010 – Planned release to nProd/Market-facing environment (market notice) Phase 5 / May 2010 – Next planned nProd release http://nodal.ercot.com 4

Scope of forthcoming changes Change - Get Reports API The existing “get Reports” API does not allow a market participant to constrain the results to a single Report ID or more specific time interval. This change will allow a report Id to be submitted as well as more flexible time interval filtering. The resulting API will closely mirror the Retail Version of this API. Note there may be performance issues with current design Change - Startup / Shutdown Instructions Schema Today, the hour ending is defined as an integer. This must be changed to string to allow the API to better represent DST (repeating hours using the * convention found elsewhere in the API for DST). Change - Dynamic Ratings API Today, this API assumes hourly reporting, which will result in a report of unmanageable size (currently disabled). This change will allow indication of Real-time in the API, which will facilitate reporting at 15 minute intervals. Change - Updated alert CM-ENGYTRD-NOTF to CM-ENGTRD-NOTF Align with MMS native notification New – Alerts Addition of DAM-DSRLDTEL-NOTF Alert (DSR Load Telemetry is lost for more than 15 mins) Addition of WRUC-COMP-NOTF Alert (WRUC completion) Remove – DC Tie Schedule Pending NPRR200 approval in February to remove requirement for schedule submission note that this is currently ready for Board consideration Functionality to be disabled only, will not be removed from spec or XSD Change- Ancillary Service values Change from “Float” to “Decimal” values to avoid scientific notation (eg, 1.6E01) http://nodal.ercot.com 5

Scope of forthcoming changes (continued) Change - Cancel Outage API with ability to include notes The existing “cancel OutageSet” API will be extended to allow the market participant to include RequestorNotes, SupportingNotes, and RASPSNotes in the request Payload. These elements will not be required. The API will still support “cancel OutageSet” without notes. The Market Manager UI will also support with and without notes. New - Get Notifications API This will be a new API available to the market but not required for consumption. It will provide a market participant with the ability to query for Bid, Resource Parameter, and VDI acceptance and rejection notifications. The API will support such features as querying by MRID, by time range, and by status (acceptance / rejection). The API will be constrained to a minimal amount of historical data availability. The API / feature set will be available via the machine-to-machine API and Market Manager UI. Opportunity Outage API Explanation: The existing Opportunity Outage API is undergoing an exercise to simplify its usage and the business logic behind it. The deltas are not yet known but are expected to firm up over February and March 2010. Once solidified, the impact will be communicated to the market. http://nodal.ercot.com 6

Scope of forthcoming changes (continued) Other Documentation Updates Combined Cycle Clarification - Minor documentation change to clarify a recurring question about when including a combined cycle name is necessary and when it is not applicable Cancel by Continuous Hour - Minor documentation change to more clearly explain how cancel by continuous hour will work and how hours are interpreted by the Market System, including DST considerations. SPPs, LMPs examples updated to remove TmPoint in example xml Text Reason - updated description to correct discrepancies. Appendix F – Updated the examples and added one for every bid type. Various Locations – updated the BidSet tables to refer to Figure 11 for supporting ASTypes Throughout the document, example XML snippets will be updated. http://nodal.ercot.com 7

Timeline for changes to EIS Specifications 1.19j Next steps Timeline for changes to EIS Specifications 1.19j Feb 2nd - NATF High-Level Overview of planned webservice changes Feb 15th - Release EIS 1.19j Specifications (redlined) & planned release timelines New External Interface Specification 1.19j and Associated XSDs Available to the Market Participants Planned delivery timeline for Market Trials Phase 4 and 5 delivery Feb 19th - Special NATF meeting to review changes to specifications Phase 4 / Late-March 2010 – Planned release to nProd/Market-facing environment (market notice) Phase 5 / May 2010 – Next planned nProd release http://nodal.ercot.com 8

Q&A / Open Forum Q&A / Open Forum http://nodal.ercot.com 9