Glossary terms

The file extension used for project files created by Logix Designer software.

The historical record of time-series data maintained by the FactoryTalk Historian ME server. It is the fundamental and most important information store of the FactoryTalk Historian ME server that contains the historical data record of all events for all points.

Any event that is stored in the archive.

A binary file that contains a section of the data archive covering some finite time range. These files, defined by start and end times, should be contiguous and non-overlapping. Only fixed archive files may be created.

A gap between the end time of one archive file and the start time of the chronologically next archive file. Archive gaps are not desirable because archive events with a timestamp during the gap cannot be stored on disk in an archive file and will be discarded. To avoid archive gaps, archive files should always be created in such a way that the end time of one archive equals the start time of the chronologically next archive.

The process of clearing the oldest writable and shiftable archive file and making it the new primary archive. An archive shift typically happens automatically when the previous primary archive becomes full, but it sometimes must be performed manually for maintenance and troubleshooting purposes.

A characteristic or parameter of a point that directs an interface and the FactoryTalk Historian ME server in the collection and processing of data values for that point.

The number of licensed points minus the total number of points already tagged for transfer. This includes tagged points from all modules that are set up to transfer data to the same PI server.

The hardware assembly that houses the FactoryTalk Historian ME module, ControlLogix processors, and other I/O modules.

An open industrial communication network initially created by Allen-Bradley/Rockwell Automation.

The base attribute that specifies the compression deviation in engineering units. This attribute specifies how much a value may differ from the previous value before it is considered to be a significant value.

The base attribute that specifies the compression maximum time, in seconds. CompMax is the maximum time difference from the previous archive event before the next event will be sent to the archive. A point is archived if the elapsed time since the previous time a point was saved is greater than the maximum time.

The base attribute that specifies the compression minimum time, in seconds. CompMin is the minimum time difference from the previous archive event before the next event is eligible to be archived. A point is archived if the elapsed time since the previous time a point was saved is greater than or equal to the minimum time and the value has changed by more than the deviation.

The process of selecting which Snapshot events will be sent to the archive for storage. Applying compression is one of the main responsibilities of the Snapshot subsystem, and the specific algorithm used is known as Swinging Door Compression.

See CompDev.

See CompMax.

See CompMin.

The three base attributes that control the compression process for a particular point: CompDev, CompMax, and CompMin. Although it is technically not included in the specification, Span affects CompDev, and Compression determines whether the specification is needed at all.

The set of identifying information on a client application seeking connection to the FactoryTalk Historian ME server. This information can include the client computer's IP address or hostname, the client application's name, or the Windows Domain name and Windows user name under which the client application is running. The FactoryTalk Historian ME server uses connection credentials to determine if there is a matching trust.

The backplane used by the FactoryTalk Historian ME module chassis.

The kind of value that will be used. Both points and point attributes have a data type. Some of the possible types include several kinds of numbers, digital, and string.

A threshold, within the alarm limit, that the rate point must pass after an alarm is triggered before the point is considered not to be in alarm.

A point type typically used when values can only be one of several discrete states, such as ON/OFF or red/green/yellow.

The fundamental unit of information used in the FactoryTalk Historian ME server. Each event consists of two main components: a value and a timestamp. The value can be one of several different data types (such as string, digital, int32, float64). The timestamp is always represented as UTC seconds and can contain a sub-second component.

A method of triggering program execution when some specific condition occurs, such as the arrival of a new Snapshot event for a particular point. Event scheduling is one method available for triggering PE or Advanced Computing Engine (ACE) calculations.

The base attribute that specifies exception deviation in engineering units. ExcDev specifies the deadband or how much a new value must differ from the previous value sent to the Snapshot subsystem on the FactoryTalk Historian ME server in order to determine whether the new value is significant and should also be sent.

The base attribute that specifies exception maximum time, in seconds. ExcMax is the maximum time difference from the last sent event before the next event will be sent. ExcMax thus effectively limits the length of time that events can be discarded because their values did not exceed exception deviation.

The base attribute that specifies exception minimum time, in seconds. ExcMin is the minimum time difference from the last sent event before the next event is eligible to be sent. Thus, the send rate of events for the associated point can be at most one event every ExcMin seconds.

See ExcDev.

See ExcMax.

See ExcMin.

The process, executed internally by the data collection, of sending events to the Snapshot subsystem on the FactoryTalk Historian ME server only when there has been a significant change in the monitored value. Significance is determined with a simple deadband algorithm.

The three base attributes that control the exception reporting process for a particular point: ExcDev, ExcMax, and ExcMin. Although it is technically not included in the specification, Span affects ExcDev.

The set of several software subsystems packaged together that constitute a single logical server application capable of storing time-series data from distributed data sources and serving this same data to client applications in real-time.

A set of security services fully integrated into the FactoryTalk Directory.

A type of archive file that allocates all of its disk space at creation time. Thus, both an empty and full archive occupy the same amount of disk space. Unless shifting has explicitly been disabled, non-empty fixed archives will participate in archive shifts.

A program written in a format resembling a ladder-like diagram. A programmable controller uses this program to control devices.

Light emitting diode. It is used as a status indicator on the module.

The NAND Flash architecture is one of two flash technologies (the other being NOR) used in memory cards. NAND is best suited to a flash device requiring high-capacity data storage. This is the data storage architecture for FactoryTalk Historian ME.

An optional text box used when defining a scan class that specifies the first time at which a scan should occur. If no offset is specified, the first scan occurs immediately after the specified interval. After the initial scan, subsequent scans continue to occur after every specified interval.

An incoming event whose timestamp is prior to the timestamp of the event currently residing in the Snapshot table for a particular point. All such events bypass compression and are written directly to the event queue.

An expression that allows a user to implement an arbitrary and potentially sophisticated calculation without formal programming. A performance equation has an intuitive syntax and may consist of standard mathematical and logical operators as well as a wide variety of built-in functions. The result of a performance equation can be archived for a PE point just like data for any other point.

A variable whose value is measurable and typically dynamic. Examples include transmitter readings, status indicators, manual inputs, control limits, etc. Each point must be assigned a unique tag on the FactoryTalk Historian ME server, and measurements of the point captured over time are effectively stored as an array of timestamped values in the data archive.

The complete list of attributes characterizing a point.

The base attribute that specifies the data type for the values that a point stores. The possible point types include the following: int16, int32, float16, float32, float64, digital, string, and timestamp. Point types can be edited after point creation, but not all type transitions are allowed.

The file that Logix Designer software uses to store a controller’s programming and configuration information. The file extension must be .ACD; if you change the extension, the file will not open.

The Module Profile is used by ControlLogix processors to identify and determine characteristics of FactoryTalk Historian ME modules.

The base attribute that specifies whether or not the interface or scanning program should collect new data for the associated point. If Scan is disabled (set to 0), then new data will not be collected.

A specification that provides an interface with the schedule for performing data collection for its associated points. The scan class specification consists of a period and an optional offset. The period determines the recurring interval when data collection should occur, and the offset determines when data collection should first start. A scan class can also optionally contain a code to force the interface to use UTC time for scheduling. A point can only be in one scan class.

The number that indicates the physical location of the slot in the chassis where the module or controller resides.

Either any event sent to the Snapshot subsystem or the event currently residing in the Snapshot table for a particular point. The event stored in the Snapshot table for each point has the most recent timestamp of all events received so far for that point; when a new event arrives with a more recent timestamp, the previous event is passed through the compression filter.

The core component of the FactoryTalk Historian ME server that receives all the new data events for all points regardless of the sending application. The most recent of these events for each point is maintained in the Snapshot table along with additional information necessary to perform compression.

The base point attribute that specifies the range or the difference between the maximum and minimum values for a point.

See Statistical Quality Control.

The SDK-based Add-In to FactoryTalk Historian ProcessBook that enables users to create and view a variety of SQC charts on their FactoryTalk Historian ProcessBook displays.

A data compression algorithm used by the Snapshot subsystem that guarantees all of the original samples were within a specified value, the compression deviation, of a straight line drawn between any two events selected for archiving. In other words, this compression algorithm allows for the reconstruction of the original signal as a series of straight lines, and the maximum error between the reconstructed and original signals is guaranteed to be no more than the compression deviation.

The base attribute that is the unique alphanumeric name for a point. Certain characters are not allowed like '*', '?', '\', and ';'. The terms

Tag

and

Point

are often used interchangeably.

A date and time, almost always associated with a data value through an event. The FactoryTalk Historian ME server stores timestamps internally in Universal Coordinated Time (UTC).

A trust allows a system administrator to configure FactoryTalk Historian ME, FactoryTalk Historian SE, or PI server to automatically allow and assign certain credentials to an incoming connection that meets the criteria defined in the trust definition without requiring a user authentication. Trusts can be used to allow connections from specific computers, applications, users, or a combination of criteria without an interactive login. Trusts are typically used to facilitate connections between background tasks such as between data and its target SE or PI server.