Approval of Federal Information Processing Standards Publication 153-1, Programmer's Hierarchical Interactive Graphics System (PHIGS)

DEPARTMENT OF COMMERCE

National Institute of Standards and Technology

[Docket No. 940541-4339]

RIN 0693-AB30

Approval of Federal Information Processing Standards Publication

153-1, Programmer's Hierarchical Interactive Graphics System (PHIGS)

AGENCY: National Institute of Standards and Technology (NIST),

Commerce.

ACTION: The purpose of this notice is to announce that the Secretary of

Commerce has approved a revised standard, which will be published as

FIPS Publication 153-1, Programmer's Hierarchical Interactive Graphics

System (PHIGS).

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SUMMARY: On June 17, 1994 (59 FR 31209-31214), notice was published in

the Federal Register that a revision to Federal Information Processing

Standard 153, Programmer's Hierarchical Interactive Graphics System

(PHIGS) was being proposed for Federal use.

The written comments submitted by interested parties and other

material available to the Department relevant to the revised standard

was reviewed by NIST. On the basis of this review, NIST recommended

that the Secretary approve the revised standard as a Federal

Information Processing Standards Publication, and prepared a detailed

justification document for the Secretary's review in support of that

recommendation.

The detailed justification document which was presented to the

Secretary is part of the public record and is available for inspection

and copying in the Department's Central Reference and Records

Inspection Facility, Room 6020, Herbert C. Hoover Building, 14th Street

between Pennsylvania and Constitution Avenues, NW, Washington, DC

20230.

This FIPS contains two sections: (1) An announcement section, which

provides information concerning the applicability, implementation, and

maintenance of the standard; and (2) a specifications section which

deals with the technical requirements of the standard. Only the

announcement section of the standard is provided in this notice.

EFFECTIVE DATE: This revised standard becomes effective August 1, 1995.

ADDRESSES: Interested parties may purchase copies of this revised

standard, including the technical specifications section, from the

National Technical Information Service (NTIS). Specific ordering

information from NTIS for this standard is set out in the Where to

Obtain Copies Section of the announcement section of the standard.

FOR FURTHER INFORMATION CONTACT:

Mr. Kevin G. Brady, telephone (301) 975-3644, National Institute of

Standards and Technology, Gaithersburg, MD 20899.

Dated: January 18, 1995.

Samuel Kramer,

Associate Director.

Federal Information Processing Standards Publication 153-1

(date)

Announcing the Standard for Programmer's Hierarchical Interactive

Graphics System (PHIGS)

Federal Information Processing Standards Publications (FIPS PUBS)

are issued by the National Institute of Standards and Technology after

approval by the Secretary of Commerce pursuant to Section 111(d) of the

Federal Property and Administrative Services Act of 1949 as amended by

the Computer Security Act of 1987, Public Law 100-235.

1. Name of Standard. Programmer's Hierarchical Interactive Graphics

System (PHIGS) (FIPS PUB 153-1).

2. Category of Standard. Software Standard, Graphics.

3. Explanation. This publication is a revision of FIPS PUB 153 and

supersedes that document in its entirety. This revision provides a

substantial, upward-compatible enhancement of the basic PHIGS

functionality known as Plus Lumiere and Surfaces, PHIGS PLUS (ANSI/ISO

9592.1a,2a,3a,4:1992). PHIGS PLUS adds facilities for the specification

of curved lines, curved and faceted surfaces, lighting and shading, and

adds a mechanism for color specification to allow non-indexed color

specification. Amendments to each part of the PHIGS specification

detail revisions required by PHIGS PLUS. Also, each language binding of

PHIGS has been amended as a result of PHIGS PLUS. The specifications

and amendments that comprise the complete PHIGS standard as a result of

this revision are detailed in the Specification section of this

document.

In addition this revision adds a requirement for validation of

PHIGS implementations using either FORTRAN or C bindings. However,

[[Page 5363]] validation is currently limited to basic PHIGS

functionality, and therefore does not include the new functionality of

PHIGS PLUS added by this revision.

FIPS 153-1 adopts the American National Standard Programmer's

Hierarchical Interactive Graphics System, ANSI/ISO 9592.1-3:1989, and

ANSI/ISO 9592.1a,2a,3a,4:1992, and 9593.1:1990, 9593.3:1990,

9593.4:1991, as a Federal Information Processing Standard (FIPS). This

standard specifies the control and data interchange between an

application program and its graphic support system. It provides a set

of functions and programming language bindings for the definition,

display and modification of geometrically related objects, graphical

data, and the relationships between the graphical data. The purpose of

the standard is to promote portability of graphics application programs

between different installations. The standard is for use by

implementors as the reference authority in developing graphics software

systems; and by other computer professionals who need to know the

precise syntactic and semantic rules of the standard.

4. Approving Authority. Secretary of Commerce.

5. Maintenance Agency. U.S. Department of Commerce, National

Institute of Standards and Technology (NIST), Computer Systems

Laboratory (CSL).

6. Cross Index.

a. ANSI/ISO 9592.1:1989, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Part 1, Functional Description.

b. ANSI/ISO 9592.1a:1992, Amendment 1, Information Processing

Systems--Computer Graphics--Programmer's Hierarchical Interactive

Graphics System (PHIGS), Part 1, Functional Description.

c. ANSI/ISO 9592.2:1989, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Part 2, Archive File Format.

d. ANSI/ISO 9592.2a:1992, Amendment 1, Information Processing

Systems--Computer Graphics--Programmer's Hierarchical Interactive

Graphics System (PHIGS), Part 2, Archive File Format.

e. ANSI/ISO 9592.3:1989, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Part 3, Clear Text Encoding of Archive File.

f. ANSI/ISO 9592.3a:1992, Amendment 1, Information Processing

Systems--Computer Graphics--Programmer's Hierarchical Interactive

Graphics System (PHIGS), Part 3, Clear Text Encoding of Archive File.

g. ANSI/ISO 9592.4:1992, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Part 4, Plus Lumiere and Surfaces, PHIGS PLUS.

h. ANSI/ISO 9592.1:1990, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Language Bindings, FORTRAN.

i. ISO/IEC 9593.1:1990 Tech. Corrigendum, Programmer's Hierarchical

Interactive Graphics System (PHIGS), Language Bindings, FORTRAN.

j. ANSI/ISO 9593.3:1990, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Language Bindings, Ada.

k. ISO/IEC 9593.3:1990, Tech. Corrigendum, Programmer's

Hierarchical Interactive Graphics System (PHIGS) Language Bindings,

Ada.

l. ANSI/ISO 9593.4:1991, Information Processing Systems--Computer

Graphics--Programmer's Hierarchical Interactive Graphics System

(PHIGS), Language Bindings, C.

7. Related Documents.

a. Federal Information Resources Management Regulations (FIRMR)

subpart 201.20.303, Standards, and subpart 201.39.1002, Federal

Standards.

b. Federal ADP and Telecommunications Standards Index, U.S. General

Services Administration, Information Resources Management Service,

(updated periodically).

c. NIST, Validated Products List: Programming Languages, Database

Language SQL, Graphics, GOSIP, POSIX, Security, Published quarterly and

available by subscription from the National Technical Information

Service (NTIS), U.S. Department of Commerce, Springfield, VA 22161.

d. FIPS PUB 69-1, Programming Language FORTRAN, adopts ANSI X3.9-

1978/R1989.

e. FIPS PUB 119, Programming Language Ada, adopts ANSI/MIL-STD-

1815A-1983.

f. FIPS PUB 120-1, Graphical Kernel System (GKS), adopts ANSI

X3.124-1985.

g. FIPS PUB 128-1, Computer Graphics Metafile (CGM), adopts ANSI/

ISO 8632:1992.

h. FIPS PUB 160, Programming Language C, adopts ANSI/ISO 9899:

1992.

i. ANSI/ISO 8632:1992, Information Processing Systems--Computer

Graphics Metafile for the Storage and Transfer of Picture Description

Information (Part 1: Functional Specifications; Part 2: Character

Encoding; Part 3: Binary Encoding; Part 4: Clear Text Encoding).

j. ISO/IEC 646:1991, Information Processing--7-Bit Coded Character

Set for Information Interchange.

k. ISO 2022:1986, Information Processing--ISO 7-Bit and 8-Bit Coded

Character Sets--Code Extension Techniques.

l. ISO 2382/13:1984, Data Processing--Vocabulary--Part 13: Computer

Graphics.

m. ISO 6093:1985, Information Processing--Representation of Numeric

Values in Character Strings for Information Interchange.

n. ISO 7942:1985, Information Processing Systems--Computer

Graphics--Functional Specification of the Graphical Kernel System

(GKS).

o. ISO 7942/Amendment 1:1991, Computer Graphics--Graphical Kernel

Systems (GKS) Functional Descriptions.

p. ISO 8805:1988, Information Processing--Computer Graphics--

Graphical Kernel System (GKS-3D) Extensions Functional Description.

8. Objectives. The primary objectives of this standard are:

--To allow very highly interactive graphics application programs using

2D or 3D hierarchically structured graphics data to be easily

transported between installations. This will reduce costs associated

with the transfer of programs among different computers and graphics

devices, including replacement devices.

--To aid the understanding and use of dynamic hierarchical graphics

methods by application programmers.

--To aid manufacturers of graphics equipment by serving as a guideline

for identifying useful combinations of graphics capabilities in a

device.

--To encourage more effective utilization and management of graphics

application programmers by ensuring that skills acquired on one job are

transportable to other jobs, thereby reducing the cost of graphics

programmer retraining.

--To aid graphics application programmers in understanding and using

graphics methods by specifying well-defined functions and names. This

will avoid the confusion of incompatibility common with operating

systems and programming languages.

9. Applicability. PHIGS is one of the computer graphics standards

(Appendix A discusses the family of computer graphics standards)

provided for use by [[Page 5364]] all Federal departments and agencies.

These graphics standards should be used for all computer graphics

applications and programs that are either developed or acquired for

government use.

9.1 The FIPS for PHIGS is intended for use in computer graphics

applications that are either developed or acquired for government use.

It is specifically designed to meet the performance requirements of

such demanding applications as Computer Aided Design/Computer Aided

Engineering/Computer Aided Manufacturing, command and control,

molecular modelling, simulation and process control. It emphasizes the

support of applications needing a highly dynamic, highly interactive

operator interface and expecting rapid screen update of complex images

to be performed by the display system. The PHIGS PLUS functionality is

designed to support graphics applications requiring lighting and

shading, curved lines, curved and facetted surfaces, and non-indexed

color specification.

9.2 The use of this standard is compulsory and binding when one or

more of the following situations exist:

--The graphics application is very highly interactive, or contains

hierarchically structured graphics data, or requires rapid modification

of 2D or 3D graphics data and the relationships among the data.

--It is anticipated that the life of the graphics program will be

longer than the life of the presently utilized graphics equipment.

--The graphics application or program is under constant review for

updating of the specifications, and changes may result frequently.

--The graphics application is being designed and programmed centrally

for a decentralized system that employs computers of different makes

and models and different graphics devices.

--The graphics program will or might be run on equipment other than

that for which the program is initially written.

--The graphics program is to be understood and maintained by

programmers other than the original ones.

--The graphics program is or is likely to be used by organizations

outside the Federal government (i.e., State and local governments, and

others).

9.3 Nonstandard features of implementations of PHIGS should be

used only when the needed operation or function cannot reasonably be

implemented with the standard features alone. Although nonstandard

features can be very useful, it should be recognized that the use of

these or any other nonstandard elements may make the interchange of

graphics programs and future conversion more difficult and costly.

10. Specifications. American National Standard Programmer's

Hierarchical Interactive Graphics System, ANSI/ISO 9592.1-3:1989 and

ANSI/ISO 9592.1a,2a,3a,4:1992, define the scope of the specifications,

the syntax and semantics of the PHIGS elements and requirements for

conforming implementations. All of these specifications apply to

Federal Government implementations of this standard.

ANSI/ISO 9592.1-3:1989 and ANSI/ISO 9592.1a,2a,3a,4:1992 define a

language independent nucleus of a graphics system for integration into

a programming language. Thus, it is embedded in a language layer

obeying the particular conventions of the language. FIPS 153-1 is

therefore divided into two parts. Part 1 represents the functional

aspects of PHIGS. Part 1 consists of the following:

(1) Functional description (ANSI/ISO 9592.1:1989) and (ANSI/ISO

9592.1a:1992, Amendment 1)

The functional description of PHIGS provides a set of functions for

the definition, display and modification of 2D or 3D graphical data. It

also provides for the definition, display and manipulation of

geometrically related objects, along with the modification of graphics

data and the relationships between that graphical data.

(2) Archive file format (ANSI/ISO 9592.2:1989) and (ANSI/ISO

9592.2a:1992, Amendment 1)

The archive file provides a file format suitable for the storage

and retrieval of PHIGS structures and structure network definitions. It

allows structure definitions to be stored in an organized way on a

graphical software system. And, facilitates transfer of structure

definitions between different graphical software systems.

(3) Clear-text encoding (ANSI/ISO 9592.3:1989) and (ANSI/ISO

9592.3a:1992, Amendment 1)

The clear-text encoding provides a representative of the archive

file syntax that is easy to type, edit and read. The file is human-

readable (allows editing), human friendly (easy and natural to read)

and machine readable (parsable by software).

(4) Plus Lumiere and Surfaces, PHIGS PLUS (ANSI/ISO 9592.4:1992)

The Programmer's Hierarchical Interactive Graphics System (PHIGS)

Plus Lumiere and Surfaces (PHIGS PLUS) extends the basic PHIGS

functionality by adding facilities for the specification of curved

lines, curved and faceted surfaces, lighting and other effects such as

depth modulation.

Part 2 of FIPS 153-1 consists of the bindings of PHIGS and PHIGS

PLUS functions to actual programming languages, defined in ANSI/ISO

9593:1990. These bindings are developed in cooperation with the

voluntary standards committees of the various languages. The following

bindings currently exist, and form part 2 of FIPS 153-1:

--The FORTRAN Language binding for PHIGS (ANSI/ISO 9593.1:1990);

--The ADA Language binding for PHIGS (ANSI/ISO 9593.3:1990);

--The C Language binding for PHIGS (ANSI/ISO 9593.4:1991).

Subsequent language bindings, including those for PHIGS PLUS, will

be added periodically as they become available. As these bindings are

approved by ANSI, each language binding will become part of this

standard.

11. Implementation. Implementation of this standard involves four

areas of consideration: the effective date, acquisition of PHIGS

software system implementations, interpretations of PHIGS

implementations, and validation of PHIGS implementations.

11.1 Effective Date. This revised standard is effective August 1,

1995. Requirements for the use of basic PHIGS functionality (defined in

ANSI/ISO 9592.1-3:1989 and ANSI/ISO 9593.1:1990, 9593.3:1990,

9593.4:1991) are unchanged and continue in effect. Validation of PHIGS

implementations is required after the effective date in accordance with

Section 11.4.

11.2 Acquisition of Implementations. Conformance to FIPS for PHIGS

is required whether PHIGS toolbox packages are developed internally,

acquired as part of an ADP system procurement, acquired by separate

procurement, used under an ADP leasing arrangement, or specified for

use in contracts for programming services. Recommended terminology for

procurement of FIPS for PHIGS is contained in the U.S. General Services

Administration publication Federal ADP & Telecommunications Standard

Index, Chapter 4 Part 1.

11.3 Interpretation of this FIPS. NIST provides for the resolution

of questions regarding FIPS for PHIGS specifications and requirements,

and issues official interpretations as needed. Procedures for

interpretations are specified in FIPS PUB 29-3. All questions about the

interpretation of FIPS for PHIGS should be addressed to:

[[Page 5365]] Director, Computer Systems Laboratory (CSL), Attn: PHIGS

Interpretation, National Institute of Standards and Technology,

Gaithersburg, MD 20899, Telephone: (301) 975-3265.

11.4 Validation of PHIGS Implementations. Implementations of FIPS

for PHIGS using either FORTRAN or C bindings shall be validated in

accordance with NIST Computer Systems Laboratory (CSL) validation

procedures for FIPS for PHIGS. Recommended procurement terminology for

validation of FIPS for PHIGS is contained in the U.S. General Services

Administration publication Federal ADP & Telecommunications Standards

Index, Chapter 4 Part 2. This GSA publication provides terminology for

three validation options: Delayed Validation, Prior Validation Testing,

and Prior Validation. The agency shall select the appropriate

validation option. The agency is advised to refer to the NIST

publication Validated Products List for information about the

validation status of PHIGS products. This information may be used to

specify validation time frames that are not unduly restrictive of

competition.

The agency shall specify the criteria used to determine whether a

Validation Summary Report (VSR) or Certificate is applicable to the

hardware/software environment of the PHIGS implementation offered. The

criteria for applicability of a VSR or Certificate should be

appropriate to the size and timing of the procurement. A large

procurement may require that the offered version/release of the PHIGS

implementation shall be validated in a specified hardware/software

environment and that the validation shall be conducted with specified

hardware/software features or parameter settings; e.g., the same

parameter settings to be used in a performance benchmark. An agency

with a single-license procurement may review the Validated Products

List to determine the applicability of existing VSRs or Certificates to

the agency's hardware/software environment.

PHIGS implementations using either FORTRAN or C bindings shall be

validated using the NIST PHIGS Test Suite, a suite of automated

validation tests for PHIGS implementations. The NIST PHIGS Test Suite

was first released in July 1990 to help users and vendors determine

compliance with FIPS for PHIGS. The most recent version of the test

suite will be used for validating conformance of PHIGS implementations

after the effective date of FIPS PUB 153-1. The results of validation

testing by the PHIGS Testing Service are published on a quarterly basis

in the Validated Products List, available from the National Technical

Information Service (NTIS). See related documents section.

Each release of the test suite has provided additional language

bindings and test cases to increase the test suite's coverage of PHIGS

functionality. Version 2.1 of the NIST PHIGS Test Suite, released in

April 1994, provides testing for PHIGS implementations using either the

FORTRAN or C language binding. Version 2.1 does not include tests for

the functionality of PHIGS PLUS added by this revision of FIPS of

PHIGS.

A PHIGS Test Suite license includes all of the tests described

above, documentation, and automatic notifications of approved changes

to the PHIGS Test Suite for a six month period. A license for the most

recent version of the PHIGS Test Suite is a necessary requirement for

an organization that desires to be tested by the NIST PHIGS Testing

Service after the effective date of FIPS 153-1.

Current information about the NIST PHIGS Validation Service and

validation procedures for FIPS for PHIGS is available from: National

Institute of Standards and Technology, Computer Systems Laboratory,

Graphics Software Group, Building 225, Room A266, Gaithersburg, MD

20899, (301) 975-3265.

12. Waivers. Under certain exceptional circumstances, the heads of

Federal departments and agencies may approve waivers to Federal

Information Processing Standards (FIPS). The head of such agency may

redelegate such authority only to a senior official designated pursuant

to section 3506(b) of Title 44, United States Code.

Waivers shall be granted only when:

a. Compliance with a standard would adversely affect the

accomplishment of the mission of an operator of a Federal computer

system, or

b. Cause a major adverse financial impact on the operator which is

not offset by Governmentwide savings.

Agency heads may act upon a written waiver request containing the

information detailed above. Agency heads may also act without a written

waiver request when they determine that conditions for meeting the

standard cannot be met. Agency heads may approve waivers only by a

written decision which explains the basis upon which the agency head

made the required findings(s). A copy of each such decision, with

procurement sensitive or classified portions clearly identifed, shall

be sent to: National Institute of Standards and Technology; Attn: FIPS

Waiver Decisions, Technology Building, Room B-154; Gaithersburg, MD

20899. In addition notice of each waiver granted and each delegation of

authority to approve waivers shall be sent promptly to the Committee on

Government Operations of the House of Representatives and the Committee

on Governmental Affairs of the Senate and shall be published promptly

in the Federal Register.

When the determination on a waiver applies to the procurement of

equipment and/or services, a notice of the waiver determination must be

published in the Commerce Business Daily as a part of the notice of

solicitation for offers of an acquisition or, if the waiver

determination is made after that notice is published, by amendment to

such notice.

A copy of the waiver, any supporting documents, the document

approving the waiver and any supporting and accompanying documents,

with such deletions as the agency is authorized and decides to make

under 5 U.S.C. Sec. 552(b), shall be part of the procurement

documentation and retained by the agency.

13. Where to Obtain Copies. Copies of this publication are for sale

by the National Technical Information Service, U.S. Department of

Commerce, Springfield, VA 22161. (Sale of the included specifications

document is by arrangement with the American National Standards

Institute. When ordering, refer to Federal Information Processing

Standards Publication 153-1 (FIPSPUB153-1) and title. Payment may be

made by check, money order, or deposit account.

Appendix A--The Family of Graphics Standards

The following computer graphics standards are now available to

address the needs of government applications in creating, modifying,

manipulating, and exchanging computer-generated pictures:

FIPS PUB 120-1, the Graphical Kernel System (GKS), which

adopts ANSI X3.124-1985;

FIPS PUB 153-1, the Programmer's Hierarchical Interactive

Graphics System (PHIGS), which adopts ANSI/ISO 9592-1989;

FIPS PUB 128-1, the Computer Graphics Metafile (CGM),

which adopts ANSI/ISO 8632-1992 and

FIPS PUB 177, the Initial Graphics Exchange Specification

(IGES), which adopts ASME/ANSI Y14.26M-1989.

In addition, the Computer Graphics Interface (CGI) has recently

become an International standard, and is expected to be issued as a

FIPS. [[Page 5366]]

These standards fall into two categories: Application Programmer's

Interface (API) standards, and Interoperability standards. The goal of

API standards is to enhance the portability of graphics programs (and

programmers) between installations and environments. The goal of

Interoperability standards is to enable graphics data to be exchanged

successfully between graphics systems and devices.

Figure 1 is a very simple reference model of a computer graphics

operating environment. The model emphasizes that a graphics application

program interacts with physical devices and human operators via a

computer graphics environment. Figure 1 also shows that the application

may receive information from an external database.

The output of the graphics program, as shown in Figure 1, is

directed to a virtual graphics device (i.e., Virtual Device Interface

or VDI) rather than directly to a physical device. A Device Driver

provides an interface, implemented in either hardware or software, for

translating virtual device commands to commands understood by a

particular physical device. By substituting one device driver for

another, an application can run on a different physical device. This

device independence is a central concept of this graphics reference

model.

In Figure 1, the API standards reside in the box labelled the

Device Independent Graphics Package. Interoperability standards are

related to the boxes in Figure 1 labelled Metafile, Database and

Virtual Device Interface. Figure 2 depicts the various graphics

standards associated with the general model shown in Figure 1. These

are discussed below.

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Application Programmer's Interface (API) Standards

Standards at the API promote program and programmer portability. A

standard at this level specifies a set of operations on a variety of

graphics objects. An API standard provides for the portability of

applications across a wide range of computer hardware, operating

systems, programming languages, and graphics devices. A program written

to an API standard at one facility in one environment should be easily

transferable to another facility in a different environment. Facility

dependencies should be the major area requiring modification.

The specific functions supported by a particular API standard

provide certain capabilities. The application programmer, by

identifying the capabilities needed, determines the API better suited

for the application. As shown in Figure 2, there are currently two

graphics API standards, GKS and PHIGS.

GKS provides a functional description of a two-dimensional (2D)

graphics interface. It provides the basic graphics support required by

a wide variety of application requiring the production of computer-

generated pictures. A procedural language binding of a functional

standard specifies the exact name for each operation, its parameter

sequence, and the data types for the parameters. FORTRAN, Pascal, Ada

and C language bindings are parts of GKS.

GKS is suitable for use in graphics programming applications that

employ a broad spectrum of graphics, from simple passive graphics

output (where pictures are produced solely by output functions without

interaction with an operator) to interactive applications; and which

control a whole range of graphics devices, including but not limited to

vector and raster devices, microfilm recorders, storage displays,

refresh displays, and color displays.

PHIGS provides for the definition, display, modification, and

manipulation of 2D and graphical data. It provides functionality to

support storage of graphics and application data in a hierarchical

form. Information may be inserted, changed, and deleted from the

hierarchical data storage with the functions provided by PHIGS.

Language binding specifications for PHIGS include FORTRAN, C and Ada.

PHIGS is specifically designed to meet the performance requirements

of such demanding applications as Computer Aided Design/Computer Aided

Engineering/Computer Aided Manufacturing, command and control,

molecular modelling, simulation and process control.

Capabilities in PHIGS but not in GKS include: the centralized

hierarchical data storage; the dynamic and responsive nature of

interactions; the addition of a modeling capability; and support for

color models other than Red-Green-Blue (RGB).

Interoperability Standards

Graphics Interoperability standards allow graphical data to be

interchanged between graphics devices. As shown in Figure 2, there are

three graphics interoperability standards, CGM, (future) CGI, and IGES.

CGM is used for the storage and transfer of picture description

information. It enables pictures to be recorded for long term storage,

and to be exchanged between graphics devices, systems, and

installations. As indicated in Figure 2, the storage mechanism for CGM

is in the form of a neutral file format called a metafile. The software

which creates the metafile is known as a CGM Generator. The software

which reads and displays a CGM metafile is known as an Interpreter.

CGM specifies a semantic interface that describes 2D graphical

entities using primitives (like polyline, text, and ellipse) and

attributes (like color, line width, interior style, and fonts). CGM is

compatible with the specification of 2D elements in GKS. A data

encoding specifies the exact sequence of bits used to represent each

operation and its parameters. CGM contains three types of data stream

encodings (binary, character, and clear text) to provide the

implementor choices depending on the particular application.

IGES provides a method for representing and storing geometric,

topological, and non-geometric product definition data that is

independent of any one system. Where CGM transfers graphical pictures,

IGES transfers a graphical database which can be processed to represent

a picture. Thus IGES represents more than just purely graphical data.

As Figure 2 indicates, the storage mechanism for IGES is in the form of

a neutral format that must be translated by a Preprocessor and

Postprocessor for conversion between systems. IGES permits the

compatible exchange of product definition data used by various computer

aided design/computer aided manufacturing (CAD/CAM) systems.

The future CGI standard is designed to specify the exchange of

information at the Virtual Device Interface. It will provide an

interface between the device independent and device dependent parts of

a graphic system. Since CGI contains information at a vitual level, it

can be used to create a CGM. A CGM can also be output on a CGI device

in a straightforward manner.

[FR Doc. 95-2103 Filed 1-26-95; 8:45 am]

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