Definitions

absent value

A placeholder that represents no value where a value is normally expected to be. For attributes, this may be an absent attribute component or a zero count. For channel samples, this is a zero count of the channel's dimension.

angular drift

One of the coordinates of the spatial coordinate system of a wellbore path. It is the angle measured eastwardly (clockwise when viewed from above) about the vertical generatrix from North.

See Figure 1.

attribute

A named item of information or data pertaining to an object type.

attribute count

The number of elements in an attribute value.

attribute label

The name of an attribute.

attribute representation code

A code that identifies the recorded representation of each element of an attribute value.

attribute units

An expression that represents the units of measurement of each element of an attribute value.

attribute value

The value of an attribute. It may be present or absent. When present, it consists of zero or more elements, each having the same units and the same representation.

base unit

a unit that cannot be expressed in terms of other units.

beginning of medium (BOM)

The point reached at the start of the tape (or partition where appropriate) after the tape is loaded or after a rewind instruction and where the first user data may be recorded. This is defined by standards or practices governing the medium.

borehole

The physical hole created by boring or drilling. The term borehole is used in a descriptive sense, as in borehole axis, borehole diameter, borehole effect, etc.

channel

A measured or computed quantity that occurs as a sequence of indexed values.

characteristic

A subitem of a component that contains one piece of information for a data item. Characteristics of an attribute component, for example, are its label, count, units, representation code, and value.

checksum

The integer result of a 16-bit cyclic redundancy computation on the the bytes of a logical record segment, excluding the checksum result itself and any bytes (e.g., the logical record trailing length) that follow it. It is used to verify possible physical recording errors in the logical record segment.

component

A construct used to implement recording the parts of a set. It contains a descriptor that specifies which kind of data item the component represents and contains subitems called characteristics that describe and contain the value of the data item. A set consists of a sequence of components.

component descriptor

The part of a component that describes its role and which characteristics are present.

component format

A value in the component descriptor that indicates which characteristics are present.

component role

A value in the component descriptor that identifies what kind of data item the component represents, which include set, object, attribute, absent attribute, replacement set, redundant set.

compound representation code

A representation code that has two or more subfields.

consumer

The system or application program or company that reads or uses RP66 information.

copy number

One of three parts of an object name. It is used to distinguish two objects of the same type in the same logical file that have the same origin and identifier.

data descriptor reference

An object name written at the beginning of an IFLR and used to associate the IFLR with the object that describes its content.

data model

A description of a specification and representation paradigm for data.

defining origin

The first ORIGIN object in a logical file.

derived unit

a unit expressed as a dimensionless scaling or as an algebraic combination of other units.

dictionary

A database in which identifiers and reference values used under RP66 are maintained and administered.

dimension

a vector of integers that describe the dimensionality and extent of the coordinate axes of an array.

EFLR

Explicitly formatted logical record. The content of an EFLR, which consists of a set of objects, is determined from an analysis of the record itself.

element

One of a list of homogeneous quantities that make up the value of an attribute or channel. Every element of a value has the same units and representation.

empty logical file

a logical file having only a FILE-HEADER set and for which the attribute END-OF-STORAGE-SET is both present and true (value = 1).

end of data flag (EOD)

A special record or condition on the tape used to indicate the end of data on the tape. This is defined by standards or practices governing the medium.

end of file mark (EOF)

A special writable record or condition on a tape that indicates the end of a tape file. It contains no data. This is defined by standards or practices governing the medium.

end of tape warning (ETW)

A warning issued by the device when the tape is nearly full. This is defined by standards or practices governing the medium.

explicitly formatted logical record

See EFLR.

fixed-length record structure

The recording of fixed-length physical records, often within larger physical blocks, on the tape. The fixed-length value can be obtained from the I/O subsystem before reading physical records. Some systems allow a different fixed length for each tape file.

format version

A two-byte field in the visible record header immediately following the length field that identifies the RP66 version of the data in the record. The version is a one-byte unsigned integer, preceded by a byte containing the value FF16.

frame

A set of channel values, one value per channel, written in an IFLR described by a FRAME object.

frame block

The set of one or more frames written in the same IFLR.

frame number

A positive integer representing the sequential position of a frame in a frame type or (if the frame type is unordered) representing a number index on the frame. The frame numbers of all frames in a frame block are written preceding the frame block in an IFLR.

frame type

The set of frames associated with a FRAME object. A frame type is represented by the FRAME object name.

identifier

One of the three parts of an object name. It is a character string used to distinguish the object from other objects of the same type. For some designated object types, the identifier conveys meaning of the nature of the object, and the identifier and its meaning are maintained in a dictionary.

indirectly formatted logical record

See IFLR.

IFLR

Indirectly formatted logical record. The content of an IFLR is determined from an analysis of related EFLRs.

locus

A sequence of distinct points in space and time, each of which has a three-dimensional position coordinate and a time coordinate.

logical file

The main unit of data exchange. It consists of a sequence of one or more logical records, beginning with a record containing a single FILE-HEADER object.

logical file section

The part of a logical file contained in one storage unit.

logical format

A description of how to encode data in a media-independent sequence of 8-bit bytes. This is the view of RP66 that is independent of any physical binding.

logical model

A conceptual organization of a domain of knowledge.

logical record

An organization of data values into coherent, semantically-related packets of information. A logical record may have any length greater than sixteen bytes and is organized in one of two syntactic forms: explicitly-formatted logical record (EFLR), or indirectly-formatted logical record (IFLR).

logical record body

An ordered sequence of bytes representing the primary data of a logical record.

logical record segment

A construct that contains the structure necessary to describe and support the physical implementation of a logical record. A logical record is implemented as one or more logical record segments. A segment is wholly contained in a visible record, but two segments of the same logical record may be in different visible records.

logical record segment attributes

The 16 bits of binary data that describe the attributes of a logical record segment.

logical record segment body

One part of an ordered partition of a logical record body into disjoint parts. A logical record body can be reconstructed by concatenating all the segment bodies of the record.

logical record segment encryption packet

The part of a logical record header that contains information required to decrypt the segment.

logical record segment header

The part of a logical record segment that describes its length, attributes, and may contain an encryption packet.

logical record segment trailer

The part of a logical record segment that contains optional padding, checksum, and segment trailing length.

logical record structure

A logical record segment attribute. It specifies whether the logical record is an EFLR or IFLR.

measured depth

The distance into a wellbore measured along a wellbore path from its wellbore path datum to a wellbore point.

See Figure 1.

object

A recorded instance of an object type.

object component

A component that delimits an object and contains its name.

object name

A three-part unique reference to an object consisting of an origin, a copy number, and an identifier.

object type

A logical entity of a schema that has a unique type name and one or more defined attributes. Instances of an object type are written in explicitly formatted logical records.

organization code

A number assigned by POSC to an organization that identifies the organization and a schema and dictionary defined and administered by the organization. See Appendix A, "Organization Codes."

origin

One of three parts of an object name. It is a number referring to a distinct ORIGIN object that contains context information for the objects that reference it.

pad count

The part of the padding (written at the end) that specifies how many padding bytes there are.

padding

Optional extra bytes following the logical record segment body used to ensure an even length for a segment and also to extend a segment when necessary to fill out a fixed-length visible record.

parent file

For a data item, the logical file in which the data item was originally created.

path

A sequence of space-time coordinates.

physical binding

A description of how RP66 visible records are recorded on a specific medium type.

physical block

A collection of contiguous data bytes recorded as a unit on the medium. A physical block is identifiable and locatable by the I/O subsystem but may not be directly visible to applications.

physical format

The medium-specific organization of data bytes on a storage unit.

physical record

A sequence of data bytes presented to an application as a unit by the I/O subsystem. An application provides the number of bytes in the record when writing and is returned the number of bytes in the record when reading. A physical record has an identifiable beginning on the medium which is locatable by the I/O subsystem.

producer

The system or application program or company that recorded information under RP66.

radial drift

One of the coordinates of the spatial coordinate system of a wellbore path. It is the angle measured eastwardly (clockwise when viewed from above) about the vertical generatrix from North.

See Figure 1.

record structure

A field in the storage unit label that identifies the kind of visible records in a storage unit.

redundant set

A verbatim copy of a set written previously in the same logical file.

replacement set

An updated copy of a set written previously in the same logical file. It includes any updates made to objects in the set since the original was written.

representation code

A unique number that identifies a standard encoding for a value as a sequence of one or more contiguous bytes.

schema

A formalized description of the encoding of information defined by a logical model, typically in terms of a data model.

schema code

A numeric code found in Appendix A used to identify the organization responsible for defining and administering a schema.

set

A collection of one or more objects of the same object type. A set is recorded in an EFLR, and each EFLR has exactly one set.

set type

The type of objects in a set.

storage set

A set of one or more storage units on which a sequence of one or more contiguous logical files is recorded.

storage unit

A medium-specific data container, e.g., a tape or file, that is identifiable and manageable by people who use the medium and on which RP66 data is recorded.

subfield

A part of a datum for which the representation is described by a simple (not compound) representation code. For example, the subfields of a datum having representation code OBNAME are origin (ORIGIN), copy (UVARI), and identifier (IDENT).

system area

An area of magnetic tape used by the I/O subsystem that is not readable or writable by applications.

tape file

A sequence of zero or more physical blocks enclosed between two EOFs or between an EOF at the beginning and an EOD at the end.

template

An ordered group of one or more attributes that represent a default or prototype object, written at the beginning of a set.

unit conversion

an algebraic transformation of a value represented in one unit to an equivalent value represented in a related unit.

unit model

a grammar in which unit symbols from an administered dictionary are combined and scaled to represent expressions of desired units.

unit symbol

a dictionary-administered word, or token, that represents a unit of measure.

update

a change in the value of an attribute previously written in the same logical file.

vertical depth

Distance measured along the vertical generatrix from the wellbore path datum.

vertical generatrix

A vertical line that passes through the wellbore path datum.

See Figure 1.

visible record

The interface between the logical format and a medium-specific physical format. A visible record has a header, a body, and a trailing length.

wellbore

A connected network of borehole within the earth. A wellbore has a minimum of one wellbore origin and one wellbore terminus.

See Figure 1.

wellbore path

A unique, non-overlapping path within a wellbore from a specific point of inception at the earth's surface to a specific point of ultimate extent in the subsurface. The wellbore path nominally follows the central axis of the physical borehole created by drilling between these two points.

See Figure 1.

wellbore path datum

The origin of the coordinate system or zero point of reference for measuring along a wellbore path to a wellbore point. Ground level, derrick floor, and kelly bushing are typical zero point references for linear measurements along a wellbore path.

See Figure 1.

wellbore point

A point position within a wellbore.

See Figure 1.