12.6 Log Topic Version1Published11/11/2016Topic Change HistoryFor StandardWITSML v2.0 Log Schema. 12.6.1 AbstractIndexValue Generic representation of pass, depth, or time values. Each derived element provides specialized implementation for specific content types or for optimization of the representation. 12.6.2 AbstractLogDataContext Defines a constraint against the data points in the log's channel. Each time the log is realized, only the data points satisfying this constraint are included. 12.6.3 Channel A channel object. It corresponds roughly to the LogCurveInfo structure in WITSML1411, and directly corresponds to the ChannelMetadataRecord structure in ETP. In historian terminology, a channel corresponds directly to a tag. 12.6.4 ChannelData Contains the bulk data for the log, either as a base64-encoded string or as a reference to an external file. 12.6.5 ChannelDerivation Specifies the source of data in a channel. 12.6.6 ChannelIndex A read-only class that is the union of those channel indexes that are shared by all channels in the channel set. 12.6.7 ChannelIndexType Specifies the type of index used by the channel. 12.6.8 ChannelSet A grouping of channels with a compatible index, for some purpose. Each channel has its own index. A ‘compatible’ index simply means that all of the channels are either in time or in depth using a common datum. 12.6.9 ChannelSetMetadata Common metadata across all channel objects. 12.6.10 ChannelState Specifies the source of the data values in the channel, e.g., calculated from another source, or from archive, or raw real-time, etc. 12.6.11 ChannelStatus Specifies the status of the channel (growing object): active, inactive, closed 12.6.12 ChannelValueContext Describes the data for the log in terms of the value of a given channel. 12.6.13 DepthIndexValue Qualifies the index as depth. 12.6.14 EtpDataType Specifies the type of data contained in a channel to facilitate data transfer using the Energistics Transfer Protocol (ETP). 12.6.15 IndexDirection Specifies the direction of the index, whether decreasing or increasing. 12.6.16 IndexRangeContext Describes the data context for a log in terms of a starting and ending index. When this context is used, each realization of the log includes all data points from the log's channel set that follow between the specified start and end index. 12.6.17 Log Primarily a container for one or more channel sets (ChannelSet). In WITSML v2.+, most of the log information is now at the channel set level. The concept of multiple channel sets in a single log is significant change from WITSML v18.104.22.168, where each log represented exactly one group of curves and their data. For more information about log organization and how it works, see the WITSML Technical Usage Guide. 12.6.18 LogChannelAxis Metadata by which the array structure of a compound value is defined. It defines one axis of an array type used in a log channel. 12.6.19 LogChannelMetadata Common metadata across all channel objects 12.6.20 LoggingMethod Specifies the method of logging used to record or produce the data in the log. 12.6.21 ObjectContext Specifies the range of index values for a log by reference to another object (or sub-object) which contains the index range as part of its data. 12.6.22 PassIndexedDepth Qualifies depth based on pass, direction and depth 12.6.23 PointMetadata Used to declare that data points in a specific WITSML log channel may contain value attributes (e.g., quality identifiers). This declaration is independent from the possibility that ETP may have sent ValueAttributes in real time. 12.6.24 TimeIndexValue Qualifies an index based on time.