Message header containing descriptive information about the message. Application level relevant time and date for when this instance of the message was produced. Source system that publishes the message. For CAISO, examples include ADS, ALFS, CAP, CRR, EMS, ETCC, FNM, IFM, MF, PI, RLC, RTM, SaMC, SIBR, SLIC, etc. All CAISO market participants are represented by Scheduling Coordinators (SCs) that are registered with the CAISO (section 5.1.2 IFM SRS). One participant can register multiple SCs with the CAISO. Many participants can do business with the CAISO using a single SC. Each generator resource can only be scheduled by one SC. One SC can schedule multiple generators. A load scheduling point can be used by multiple SCs. Each SC can schedule load at multiple scheduling points. Each SC can have more than one load schedule at any load scheduling point as long as each load schedule at the same load scheduling point has a separate resource ID and settlement-quality meter. An inter-tie scheduling point can be used by multiple SCs. Each SC can schedule interchange at multiple inter-tie scheduling points. An SC can have multiple interchange schedules at the same inter-tie scheduling point by assigning a unique interchange identifier to each interchange schedule. Currently, the type of SC includes: Scheduling Coordinator (MDAS certified) SC of Inter-SC Trades Only (not MDAS certified) SC & FTR holder SC, FTR holder, TO , & UDC. MRID stands for master resource identifier which should be globally unique.