Archaeological Computing: Unified Glossary

Archaeological Computing

Unified Glossary

Individual Chapters in Archaeological Computing have glossaries; this unified glossary is simply a combination of those glossaries into one alphabetized list. It may not be particularly useful to anyone who has not read the book.

Please note that the terms defined in more than one chapter glossary are shown here with both definitions and an indication of the relevant chapter for each definition.

4th Dimension: a Windows and MAC database management system.

Access: Microsoft database management system for PCs; sold as a part of the MS Office suite.

Analog: information represented in forms that are or appear to be continuous, as opposed to digital information, which is or appears to be discrete. An analog watch represents the time precisely but with moving hands instead of displayed numbers; a digital watch represents time no more precisely but with numbers only. Digital displays seem more accurate/precise, but that is not necessarily so. (See digital.)

Application: a computer program intended to carry out real work for typical computer users, e.g., a word processor, a GIS program, or a Web browser. (See software; compare operating system.)

Archival copy: a copy of a file intended for long-term storage and retrieval.

ASCII : American Standard Code for Information Interchange; a standard for using eight computer bits as a unit (byte) to represent numerals and letters. This system is a standard that has long been used in personal computers. An eight-bit byte can create only 2 to the eighth power different characters (256), and only half of those - 128 characters - is actually defined by the system because, at the time the standard was defined, the last of the eight bits in each byte was used only as a transmission check. The last bit is no longer used as a check, making it possible to represent 128 more characters with the same 8 bits. Unfortunately, the standard having been defined already, the added 128 characters have been defined idiosyncratically by manufacturers such as Apple and Microsoft. Those definitions are not uniform. (See ISO standards.)

Atomize: break data into its smallest constituents, e.g., using the categories street address, city, state, and zip, not just one large category called address with all the pieces of the address included.

Attachment: a computer file sent along with - attached to - an email message.

Attribute (Database Chapter): in databases, a specific characteristic of an item; see column.

Attribute (GIS Chapter): equivalent to a field or column in a data table and also the standard English usage; an attribute is simply a characteristic of something.

AutoCAD: one of the most common and widely-used CAD programs, produced by Autodesk, Inc. AutoCAD was originally available for UNIX computers as well as PCs, and a MAC version was produced for a short time. It is now available for Windows only.

Back-up: a secondary copy of any computer file, a copy intended to be used if the original is damaged or lost.

Binary: a number using two as its base (rather than ten, the base for the decimal system). Thus, 1111 in a binary system is equivalent to 15 in the decimal system.

Bit: a single electronic signal, binary in nature (on or off only, treated as zero or one).

Block: in AutoCAD and some other CAD programs a defined object, consisting of any number of entities, that can be inserted into a model at any point, on any layer, and at any scale or orientation.

Buffering: An operation that creates rings of specified distance from the selected entity. If the entity is a point then buffering creates a set of bull's-eye type rings.

Bus: the electronic conduits connecting various internal parts of computers so that information may be moved between/among them.

Byte: a group of bits (usually eight) treated together as a discrete entity.

CAD: computer-aided or computer-assisted design software and/or computer-aided drafting software.

CD (rom): a removable storage medium for binary data that is encoded with optical signals rather than magnetic ones. The data may represent information (data) or instructions (software). Most CDs cannot be changed once the optical codes have been inscribed, though the CDs called CD-RW can be changed or re-written. The CDs that cannot be changed are excellent back-up devices precisely because they cannot be changed.

Cell (Database Chapter): an individual field or column entry for a single row (a term more often used in spreadsheets than databases).

Cell (GIS Chapter): a square or rectangular unit of the earth’s surface defined by a GIS system so that data about the area encompassed can be attached to the cell. Cells are equivalent to pixels in some forms of imagery.

Child Table: a table related to another in a many-to-one (child-to-parent) relationship.

Codd, E. F.: an IBM scientist who first set out formal rules for so-called normalization of databases, rules intended to prevent errors from entering the data and to prohibit data duplication.

Column (field): the particular attribute stored about each unique item in a table.

Control point: a specific location for which the x, y (and often z) values are known so that it can be used to orient an image or map properly. See rectification.

Coordinate system: a system for supplying mathematically precise coordinates for any point on the earth. A coordinate system must be based upon a chosen datum to retain its accuracy, and it may be related to a specific projection. (UTM and state plane are examples of coordinate systems.)

Cost Surface (Friction Surface, Movement Surface): a measure of the effort/expense/time required to traverse and area because of impediments to travel.

Coverage: A term used in earlier versions of the ArcInfo GIS software system for a feature class or layer.

CRT: cathode-ray tube. Old-fashioned TV-style display device, for displaying images on the nearly flat surface of a vacuum tube. (See LCD.)

Datum: a mathematical representation of the shape of the earth. A datum must lie at the heart of any system intended to model the earth, but no datum is completely accurate; therefore, several are in common use.

dBase: the first popular database application for PCs.

DBMS : database management system.

DEM: digital elevation model, a grid of elevation values, equivalent to DTD or digital terrain data.

Digital: based on digits (usually assumed to be binary digits only) and assumed to be electronic, magnetic, or optical in form, i.e., created by and used in computers.

Digitize: in more general usage, to translate information into digital form; in graphics applications to trace a drawing, map, or plan to create a digital version of the original.

Digitize (GIS and CAD Chapter): 1) to convert from analog to digital form, generally in some automated fashion; 2) to convert manually from an analog original into a digital format, as when plans or drawings are copied with a digitizing tablet or scanner.

Digitizing tablet (digitizer) (GIS and CAD Chapter): an electronic drawing tablet connected to a computer. The tablet can function as a mouse, controlling cursor movement in a relative sense. With many CAD programs a digitizer can also be scaled so that it functions more like a drafting board. (A digitizer that has been scaled may be used to digitize a paper drawing; such a drawing, placed on the digitizer, may be traced to create a digital version of it.)

Directory: a hierarchical grouping of files or of other (sub-)directories considered to belong together for any reason. Directories and sub-directories are defined by users. (In MAC systems, folder.)

DOS (Disk Operating System): an operating system that assumes the presence of a disk, either a floppy disk or a hard disk to store the operating system software. (MS-DOS is the name of the disk operating system originally made by Microsoft, an abbreviation for Microsoft disk operating system.)

DTD: digital terrain data, a grid of elevation values, equivalent to DEM or digital elevation model.

DVD: similar to CDs, but DVDs can store several times as much information as CDs.

DWG: the file format for CAD files used by AutoCAD. It has become an industry standard and is often specified by government agencies. The format is not without its drawbacks, even when used within the Autodesk program family. Some programs produced by Autodesk in the past, for instance, extended the capabilities of basic AutoCAD and added new ways to model entities, but entities not supported by the basic version of AutoCAD. Using a DWG format document in another program has some inevitable problems because of differences in the ways various programs operate and the kinds of entities they support.

DXF: drawing exchange format. A file format developed by Autodesk but made public. This is a widely used exchange format, permitting model entities to be moved easily from one model/program to another. Some complex model entities may not be supported.

Entity: a generic term for any portion of a CAD model that is treated as a single item for the sake of copying, moving, or editing. A line, a rectangle, or a circle may be an entity, but so may a group of lines (if created as a group), or a surface (bounded by lines), or a solid.

Extension: the portion of a file name in Windows (and now commonly in other systems as well) that follows a period and indicates the file type.

Feature Class: See layer (GIS Chapter).

Field: equivalent to column.

File: a single digital document; in database usage, a table may be stored in digital format as a single data file. Modern databases often store many tables in a single, complex computer file.

File Format: the specific encoding system used for a digital file and agreed upon by all who create or use files of that type. A file cannot be decoded by software unless the software designers know the decoding system.

FileMaker: A database management system made for Windows and MACs by a subsidiary of Apple.

Firewall: hardware and/or software lying between a computer and the Internet to protect the computer from unauthorized access via the Internet.

Flash Memory: non-volatile electronic memory. Solid state memory devices that were very expensive, measured by the cost per unit of memory, but are now becoming less so and are being used to hold information such as digital images. CompactFlash, SmartMedia, Sony's memory stick, and xD-Picture Card are the current commercial versions available for digital cameras.

Flat file (database): a database table that is complete on its own and needs no other tables to make it useful.

Floppy Disk: a storage medium for storing binary codes using magnetic signals. The codes may represent data or software. The magnetic coding can be changed at will (intentionally via the computer operating system but also, intentionally or accidentally, by any magnetic field). Floppy disks were developed to make it possible to transfer data or programs easily from one computer to another. (Original floppy disks were actually floppy, not rigid. The magnetic material was on a thin substrate that was not rigid, and the magnetic material and substrate were held within a paper package that added little rigidity. Current versions are rigid, since the magnetic material, though still not rigid itself, is held within a rigid plastic package.)

Folder: the Apple/MAC term for directory.

Foreign key: a column (field) in one table that is used to identify a related row in another table.

FoxPro: a database management system based on some dBase standards and widely used in many areas because of its flexibility (and its longevity). This is a Microsoft product, and Microsoft has announced that it will not be updated in the future. User support will continue until 2015.

Freeware: software available without payment.

FTP (file transfer protocol): a system developed very early in the history of computer networks to enable the transfer of a digital file from one computer to another over a network. It is the file transfer system used on the web, though that is not made explicit to users.

GIS: geographic information system.

GUI (Graphical User Interface): any system designed to permit users to direct a computer program with a pointing device (typically a mouse) and a variety of visual cues at which to point. Now more widely taken to indicate the system of visual cues and presentation formats created to aid users of a computer.

Hard Disk (Hard Drive): a storage device for digital codes in magnetic form. The codes may represent data or software. The magnetic coding can be changed at will (intentionally via the computer operating system but also, intentionally or accidentally, by any magnetic field). The hard disk actually consists of a thin magnetic material on a substrate; the disk revolves at very high speeds while sensitive devices analogous to tone arms on old record players either measure the existing magnetic pulses on the magnetic material (to obtain data from the disk) or change the magnetic pulses (to put data onto the disk). What is colloquially called a hard disk usually consists of several disks rotating together on a common spindle as well as the mechanisms for rotating the disks, reading data, and writing data. Hard disks are normally not removed from a computer unless they have malfunctioned; they are sealed units. However, the entire unit may be removed, and hard disks in portable computers may readily be moved from one computer to another.

Hardware: the physical components of a computer, e.g., monitor, disk, keyboard.

Hidden-Line Drawing: a drawing (usually a 3D one) that suppresses those lines in the model that should not be visible in the chosen point of view. (See wire-frame.)

Internet: the cables (and now wireless connections) and routing boxes that permit computers connected thereto to send signals to one another. The Internet is a huge, world-wide network. Some computers on the Internet may do nothing more than supply files. Others may use more demanding communication protocols to carry out cooperative tasks.

ISO Standards: International Standards Organization standards, including those that specify computing codes. Similar to ASCII, the ISO standards numbered 8859-1 through 8859-15 specify characters for eight-bit byte systems (256 characters). The ASCII standard is used for the first 128 characters of all ISO 8859 standards, but the remaining 128 characters are different for different scripts, making it possible for people to use different versions of the ISO 8859 standard for different languages, e.g., modern Greek or Cyrillic. (See ASCII.)

Java: a computer language that has been implemented so as to permit a program written in that language to operate on any computer with the proper Java system. A Java application will therefore run on Windows, Linux, and MAC computers.

Join: the basic term used to describe combining the content of two related data tables. There are several kinds of table joins.

JPEG (JPG): the file format developed by the Joint Photographic Experts Group for photographs. This is a compressed format, and there is some loss of image information when a file is compressed via a JPEG algorithm.

Key field: a column (field) that is indexed.

LAN (Local Area Network): a network that is both relatively small and confined as to geographic area covered. All computers in a LAN are controlled by the same people/organization; so the level of cooperation can be extensive, although such levels of cooperation require some expertise on the part of the network administrators.

Layer (Level) (CAD Chapter): in CAD parlance, a portion of the model separated from others for any reason whatsoever, be it spatial, temporal, chronological, or conceptual. Layers can be included or excluded in any view or paper drawing, individually or in groups. Layers are critical in the scholarly use of CAD.

Layer (Theme, Feature Class) (GIS Chapter): a portion of the GIS data separated from others for any reason whatsoever, be it spatial, temporal, chronological, or conceptual. The GIS layer is roughly comparable to a table in a database.

LCD (Liquid Crystal Display): The flat-panel display types used in laptop computers and now on many desktops as well. Their primary advantages are size and weight, when compared to TV-like cathode-ray-tube monitors. (see CRT.)

Line: a basic element of vector data composed of the connection of two or more pairs of x and y (and sometimes Z) values.

Linux: an operating system based upon UNIX and maintained by an open standards committee. There are versions of Linux for PCs as well as Apple Macintosh computers and larger, more powerful machines. Much software for Linux is free. The operating system itself is available for free. (See open source.)

Lookup table: a table used to provide a limited selection of choices with which to fill a column (field) in another table.

Macintosh: Apple's personal computer. The Macintosh operates with a different operating system than the PCs using Windows or MS-DOS (still used in some places, though more and more rarely). Users of Macintosh computers normally use software designed for the MAC operating system, the current version of which - OS X - is based on UNIX. The latest iterations of the MAC can also run Linux and Windows and their applications.

Malware: the general term for computer programs designed to damage computers or to gain control of them for an outsider. Viruses are one category; they are programs designed to damage the computer, usually to no purpose. Some viruses allow outsiders to use an infected computer for their purposes, not the owner's. Worms are designed to propagate themselves through the network, often doing no damage in the process. Trojan horses are the programs that carry surreptitious code within them for unexpected purposes, often to detect and pass on to others the keystrokes used, enabling passwords to be harvested.

Many-to-many relationship: the relationship of a column (field) in many rows (records) of one table to a column (field) in many rows (records) of another table. This complex relationship is the most difficult table-to-table relationship encountered in a relational database management system.

Many-to-one relationship: the relationship of a column (field) in many rows (records) of one table to a column (field) in a single row (record) of another table. A table with information about many children has a many-to-one relationship to a table containing information about the women who are the mothers of all those children. (Note that some of those women may have no children; others one. But the nature of the connection permits an undefined and unlimited number of children to be linked to any woman.)

Metadata: data about data. Some take the term to indicate the kinds of information that might appear in a library card catalog

Microstation: a widely-used CAD program produced by Bentley Systems, Inc. Microstation was available for MACs as well as PCs for many years but is now available for Windows only.

Model: a CAD creation or file. Even the simplest CAD creation is too complex to be called a drawing, a term that suggests a single, discrete view of something; so the term model is preferred. A drawing is a single version of the model, reduced to screen or paper, representing the model from one point of view and at one scale.

Monitor: the television-like, CRT viewing apparatus for a computer or an LCD serving the same function. (See CRT, LCD)

Multi-band imagery: Digital imagery composed of measurements from multiple portions of the electromagnetic spectrum. A common example is an RGB image with separate values for the red, blue and green portions of the spectrum. When combined, the result is a full-color image. Other examples are CIR (color infrared) and multi-spectral, such as many satellite images.

Multi-spectral images: See multi-band imagery.

MySQL: the most commonly used database management system with Linux.

Network: a set of wiring, wireless transmission systems, and communication protocols allowing computers attached thereto to communicate with one another and possibly even work cooperatively. The extent of the communication/cooperation is determined by the protocols used and may be limited to such mundane things as file sharing or be as extensive as allowing individual computers to work on the same project simultaneously. The physical extent of the network is adjustable; a network may include only the computers in a small office, those in a large building, or something as large as the Internet.

Normal(ize): organize data in tables to avoid duplication and to make sure that queries create correct responses. There are very specific requirements for various levels of normalization.

Object-oriented database: a form of database design that is informed by a hierarchical organizational scheme such that any item can be described, at least in part, by the characteristics of those above it in the hierarchy. This is not an approach recommended by the author, and it is not be discussed in the book.

One-to-many relationship: the relationship of a column (field) from any given row (record) in one table to a column (field) in many rows (records) of another table. The reverse of the many-to-one relationship, this relationship would relate a table with information about mothers to the table of all their children.

One-to-one relationship: the relationship of a column (field) from any given row (record) in one table to a column (field) in a single row (record) of another table. This rather simple relationship would relate two tables with information about the same subject or two tables with information about different subjects, but neither table having multiple entries about the object in question.

Open Source: software that is supplied with its actual code accessible, permitting users to modify that code. Normally, any such modification must be shared, at no cost, with any other users. Open source software is usually available at no cost, though it may also be purchased with aids for installation or service assistance.

Oracle: a database management system often used in very large corporate settings. It is not recommended for individuals without training in its use and access to good technical support.

Orthorectification: A multi-step process that first removes the distortion due to optical properties of a camera and lens (see rectification) and then removes distortions that are due to elevation differences across an image. The result is an image for which accurate ground measurements can be made across the entire image.

OS (Operating system): the basic program that must be loaded into a computer at start-up to prepare the computer for doing useful work. The operating system determines how the physical parts (hardware) of the computer communicate and interact. Applications such as word processors or web browsers operate on the computer via the operating system; so they need not operate directly on the hardware. Therefore, application software is usually written for specific operating systems.

OS X: the operating system, based on UNIX, for current Macintosh computers.

Overlay: a process that places a second layer over a first either to create a new combination of both or to select items in the first that have a relationship with items in the second, for example all the findspots in one layer that are inside the soil polygons in the second.

Parent table: a table related to another in a one-to-many (parent-to-child) relationship.

Partition: a physically distinct portion of a hard disk that the operating system can treat as if it were a separate hard disk.

PC (Personal Computer): used generically to include the Macintosh and Linux computers here unless a clear distinction is stated; the term is often used to include only computers running Microsoft Windows.

Planar: having to do with a single plane in space; flat and lacking modulation.

Point: the basic element in vector data, a single pair of x and y values. It may also include a z (or height).

Polygon: one of the basic elements of vector data, along with point and line. A polygon is a closed area bounded by lines that meet at the corners (vertices) of the polygon; a polygon is defined by its vertices.

PostGreSQL: a widely used database management system for Linux.

Primary key: an indexed column (field) that is unambiguously the subject of the attributes in the row (record) and that signifies one and only one row (record) in the table; to be unambiguous the content of the column (field) must be unique. It is possible to construct a primary key from two or more columns (fields) in the table.

Projection: the method used to project the nearly spherical shape of the earth onto a flat surface such as a piece of paper. All projections distort geography to one degree or another.

Proprietary (Format): a digital file format controlled by a corporation. Such formats may be licensed to others, but the controlling corporation will not permit use of the format without permission and may change that format without notice.

RAM: random access memory. Electronic memory within a computer that may be found via a numeric address and therefore can be located directly, without looking through other memory locations. RAM is volatile; when electricity is turned off, the signals are gone.

Raster: a term used to describe an image that consists of individual points of color or shades of gray. A standard photograph or a satellite image is a raster image.

Reclassify: a process that converts values in in a map or file to a new set of values based on a set of rules or operations. For example, all elevation values in a map that are greater than 100 may be reclassified as high in a new map.

Record: equivalent to row.

Rectification: the removal from an image of optical distortion created by a camera and lens. See also orthorectification.

Register: Apply known locations to selected points (usually four or more) in an image or map. The first step in one form of rectification.

Relational database: a set of related data tables, each of which depends on others in some way for completeness.

Rendering: a three-dimensional view that includes artistic effects, possibly including shadows and even reflections, to make the result appear more lifelike.

Repeating field: a column (field) that has multiple independent values as attributes for the item in the row (record).

Resolution: in GIS systems resolution refers to the size of the individual cell to which data may be attached. At 10 m. resolution, the cell is 10 m. x 10 m., or 100 square meters.

ROM: read only memory. Non-volatile electronic memory that cannot be changed. (There are variations called EPROMs, for electronically programmable ROM, that can be changed, but changing an EPROM is intentionally rather difficult. EPROM memory is not volatile.)

Root: in Windows the broadest designation of the content of any given disk; the root directory contains all other directories on that disk. In UNIX and UNIX-derived systems, the root directory is not limited to a disk; it is the base directory in which ALL other directories exist. (A second or third hard disk in a UNIX system is considered to lie in a directory within the overall system.) In UNIX systems access to the root directory is limited to systems managers to prevent accidental tampering by users.

Row (record): the collection of attributes of a particular, unique item in a table.

Scanner: normally used to indicate a device that measures tone or color on a piece of paper or film to create a digital version of the original, much as a photocopier might produce a paper copy. New 3D scanners detect the location of points in space rather than tone or color on paper. They use reflected light beams to calculate point locations on any object in the area at which the scanner has been aimed. The 3D locations of all points in the field of view are measured, much as they might be with a surveying instrument. The points located, however, are not individually selected; they are the points selected automatically according to the grid resolution. Scanner resolution varies with the distance from the object and may, with some scanners, be manually adjusted.

Select: use attributes or geometry or both to identify some elements in a layer. The resulting elements are referred to as a select set.

Server: a computer designed to hold data for other computers to access over a network.

Shape file: An ArcView file format for vector data. The shape file is actually multiple files in a single computer folder. These include geometric data in a file.shp and attribute data in a file.dbf as well as others.

Shareware: software that is available, without advance payment, for use/trial and for which a voluntary payment is expected if the software remains in use.

Snapping: a process that connects lines that are close to each other. A line that comes with in a specific distance of an original line may be snapped to the first.

Software: program code that will cause the computer to perform requested functions. (See application; OS, operating system.)

Solid Model: a model that explicitly includes objects defined as solds (as opposed to surfaces or lines only). A solid model may include simpler entities - lines or surfaces - as well as solids.

Spam: unwanted email, usually messages aimed at selling products but often scams of one sort or another.

Spline: a continuous curve drawn through or near specified points. There are various forms of splines, all of which create a continuous curve. Depending on the mathematical representation used, the curve may pass through all points (non-rational B-spline) or only near those points (cubic or quadratic splines).

Spreadsheet: a digital file very similar to a digital data table but with the possibility for including specialized formulae in the table as well as data. The term is also used to denote the kinds of programs that create spreadsheets.

SQL (Structured Query Language): the defined standard syntax for accessing data from tables.

Surface Model: a model that explicitly includes surfaces (as opposed to only lines, some of which may bound surfaces). A surface model may include lines or other simpler entities as well as surfaces.

Table: a collection of information organized into rows of data, each row concerning a unique item, and columns, each column containing a specific attribute of the items.

Theme: See layer.

TIFF (TIF - tagged image file format): a standard file format for images. Moving an image to this format should entail no loss of image information.

Topology: the relationships of areas, lines, and points to one another.

Total Station: a surveying instrument that combines an electronic version of the traditional theodolite with an electronic distance measuring device (often called an EDM) so that the 3D location of a point in space may be determined. Some total stations require a reflecting prism at the point to be surveyed. Others can survey a point on any surface that reflects enough light.

Unicode: a replacement for ASCII using 16 bits per character and consequently 216 possible characters (65,536). It was once thought to be capable of representing all scripts and symbols, but there is already a Unicode standard based on 32 bits per character so that there really will be enough characters for all scripts, even hieroglyphics (4,294,967,296). (Unicode is equivalent to ISO-10646, which established both 16-bit and 32-bit standards.)

Unique column (field): any column (field) for which each entry must be unique.

Vector: a term used to describe an image that consists of vectors, lines (curved or straight) that can be defined mathematically and therefore reproduced at any scale on command.

Vertex: the point where two lines composing a polygon meet.

Visibility map (viewshed analysis): a map showing areas of terrain that can be seen from a given point.

Vista: the latest iteration of Windows, this operating system has been advertised as safer and more robust then prior versions of Windows. At this writing, the jury remains out as to its value.

Volatile: in the computer world, referring to a form of memory that requires electricity to function. When electricity is lost, anything stored in a volatile device is also lost.

Voxel: a three-dimensional cell, normally having the same resolution in all three dimension.

VR (virtual reality): not really a CAD term, virtual reality refers to systems that use 3D models such as those produced by CAD programs but add the ability to navigate through a model in real time. VR programs often permit such navigation through a rendered version of the model, making the result very life-like.

WAN (Wide Area Network): a network covering a wide geographical area. WANs often use public networks such as the Internet to connect LANs to one another, forming a WAN. The Internet can be described as a WAN, but the term is normally taken to define a more centrally controlled network such as one set up by a specific company or institution.

Web: the portion of the Internet and computers connected thereto that supplies documents according to certain standards. Those standards permit the documents to be displayed by anyone with access to the Internet and appropriate software.

Wetware (Grayware): a pejorative term for the human brain, often used when referring to the person operating a computer (who is considered less reliable than the computer, an assumption that may or may not be accurate).

Windows: the combined operating system and graphical user interface made by Microsoft and used on those personal computers that trace their ancestry to the original IBM personal computer. More generically, windows are the individual, bounded portions of a computer display in which a particular program or document may be used or seen.

Wire-Frame: a three-dimensional modeling process or drawing type that deals only with lines in space, not surfaces or solids. A wire-frame view of a model (even a surface model or a solid model) shows all lines and edges, whether or not they should be seen from the chosen point of view.