Data interchange services provide specialized support for the interchange of data among applications. These services are designed to handle data interchange between applications on the same platform and applications on heterogeneous platforms. The data interchange service standards adopted by the DODIIS community are categorized by the type of data and listed in table 2-4 .
One of the DODIIS core data design standards is the Military Intelligence Integrated Data System (MIIDS) model, defined in the DIA MIIDS and Integrated Database (IDB) Definition and Specification Document (Parts I, II, III, and IV). The MIIDS defines an architectural concept for improving the manner in which general military intelligence data is analyzed, stored, and disseminated over a series of integrated databases at every level of command. MIIDS provides a framework which addresses the logical database structure, data element and content standardization, and data exchange formats to allow for the rapid exchange of information between producers and consumers of intelligence information. Within the MIIDS concept, the Integrated Database Transaction Format (IDBTF), defined in DIA DDS-2600-6245-89, specifies the standard transaction format for exchanging MIIDS data. The IDB Extract File Format (IDBEF), which is defined in DDS-2600-5994-88, specifies the format for bulk data transfers and initial loads of site IDBs.
The Intra Boundary Format (IBF), developed by DIA and documented in Communication and Message Profile Header Format Specification , is the DODIIS message header format standard for exchanging messages among networked components internal to a DODIIS site. For the body of formatted messages, the United States Message Text Formatting (USMTF) standard as defined in Joint Pub 6-04 is adopted. The USMTF applies to all character-oriented message text formats used in support of joint and combined operations. Message dissemination is accomplished using the protocol suites discussed in section 2.6 .
Standards in this component address the transfer and sharing of the values and syntax (i.e., format or grammar), but not the semantics (i.e., meaning), of data records between communicating systems. The specifications are independent of the internal record and field representations for the communicating systems.
Table 2-4 . Data Interchange Service Standards
ISO 8824:1987, Specification of Abstract Syntax Notation One (ASN.1), is adopted by DODIIS so that two programs residing on different hosts and written in different programming languages can communicate independent of either system's internal representation or the representation used for transmission. This standard allows the programs to specify a structure and values for the records they exchange, in a so-called "abstract syntax". The records they use to communicate are called Protocol Data Units (PDUs), and ASN.1 makes it possible to specify the abstract syntax of any standard's PDUs.
Also adopted is a companion standard ISO 8825:1987, Specification of Basic Encoding Rules (BER) for Abstract Syntax Notation One (ASN.1). The BER is the most general, although not the most efficient, bandwidth encoding scheme that allows encoding of the ASN.1 data, in order to produce an actual stream of bits that can be transmitted from an application on one system to a peer program on another. The BER uses a type, length, and value encoding scheme where each value of an ASN.1 data type is accompanied by its type and length. Hence, each value identifies its own type and can be any length since it carries its own length.
DODIIS adopts Request for Comment (RFC) 1014: XDR (External Data Representation) as a means of supporting Sun Open Network Computing (ONC) RPC and the Network File System (NFS), which use XDR to describe the format of the data. The RPC standard currently under development by the ISO (ISO 11578) is expected to eventually be adopted by DODIIS, at which time XDR will also be replaced by the appropriate standard as dictated by the ISO 11578. See section 2.6.1.6 for a detailed discussion of RPCs.
Text data is the medium encompassing a character-based encoding only. Text data also addresses character sets and character strings, as opposed to higher level entities such as documents which contain characters and character strings.
For the interchange of text data, DODIIS adopts American National Standard Code for Information Interchange (ASCII), which is both an ANSI and ISO standard, with respective references to ANSI X3.4, American Standard Code for Information Interchange (ASCII) , and ISO/IEC DIS 10646, Universal Multiple-Octet Coded Character Set (UCS). ASCII is defined as the lower eight bits of the UCS, with one byte of leading zeros and is therefore fully compatible with the ISO 10646 standard. ASCII permits the presentation of English in computer-based systems, and its unambiguous interchange between systems. ASCII is thus adopted by DODIIS to represent, process, store and present text.
Standards in this component describe documents, which can have two kinds of structures associated with them as follows:
The data format of WordPerfect 5.1 should be used for interchange of office documents within the DODIIS community. Although the Office Document Architecture (ODA; ISO 8613:1989) defines a comprehensive architecture for document interchange, including logical structure, layout structure, and presentation, the U.S. vendors have virtually ignored this standard in favor of their own proprietary formats. Also, the potential ODA market has partially been satisfied by the Standard Generalized Markup Language (SGML) discussed in section 2.4.5.2 . As such, the ODA and related ODL/ODIF, previously cited in the DODIIS Profile, are being withdrawn.
Standard Generalized Markup Language (SGML: ISO 8879; FIPS PUB 152) is a metalanguage for describing the logical structure of documents in a hardware and software independent manner. It provides a means to specify, on the particular markup, what is allowed, what is required, and how the markup is to be distinguished from text. SGML provides the flexibility to tailor custom document types by creating Document Type Definitions (DTDs). A DTD defines the structure and the rules for marking up a class of documents, by stating the names and contents of permissible elements, the order and frequency of the elements, and the attributes associated with the elements.
In general, SGML is only concerned with the logical structure, needing a way to describe the formatting aspects of the documents marked up in SGML. For this purpose, the ISO is currently developing Document Style Semantics and Specification Language (DSSSL: ISO/IEC DIS 10179), which will complement SGML by providing a means to describe the layout or formatting structure of documents in a way that ensures application and machine independence.
As such, all DODIIS users of SGML who require formatting information to be exchanged should adopt DSSSL for the interchange of formatting information, upon its expected completion in 1995.
In order to use SGML and DSSSL, the DODIIS community needs to develop a comprehensive tag set and DTDs. As it is costly and time-consuming to develop a new tag set and DTDs, DODIIS will utilize existing tag sets and DTDs as a baseline, such as HTML used on the Internet and the Computer-Aided Acquisition and Logistics System (CALS) tag set and DTDs.
HyperText Markup Language Plus (HTML+) provides a set of SGML tags and a DTD for the Internet community to markup data and embed hypertext links for navigation through the data available on the Internet. See section 2.6.1.5 for more discussion on HTML+ in relation to other Internet protocols.
The CALS SGML is defined in MIL-M-28001, Military Requirements and Generic Style Specification for Electronic Printed Output and Exchange of Text. Appendix A of MIL-M-28001 contains a comprehensive tag set and DTDs that define the logical structure of various types of documents; Appendix B, Output Specification, addresses the layout structure and provides output DTDs that can be applied to format documents which are marked up with the tags defined in the Appendix A.
DODIIS will closely monitor efforts such as Combined Intelligence Publishing Service (CIPS) and Community Management Staff/National Intelligence Council (CMS/NIC) Electronic Publishing Initiative to maximize interoperability within the national intelligence community. Combined Intelligence Publishing Service (CIPS) program is in the process of identifying publishing standards to facilitate production and interchange of finished multimedia intelligence products that are device and application independent. The CMS/NIC Electronic Publishing Initiative is working toward establishing an SGML resource center for a tag library and DTD registrar for the national intelligence community.
Hypermedia/Time-based Structuring Language (HyTime; ISO 10744/ANSI X3V1.8M) is an extension of SGML to deal with hypermedia document interchange in a time-based manner. Currently, there are only a few products which implement limited features of HyTime. As such, DODIIS will monitor the HyTime market for possible adoption in the future.
For the interchange of composed document data, DODIIS adopts Standard Page Description Language (SPDL: ISO 10180:1992). SPDL provides an unambiguous method to describe the two-dimensional image of document pages for the display on a terminal screen or printing on a hard copy device. This is called the "final form" or "non-revisable" form of the document. SPDL describes the physical page layout of the document rather than the logical structure of interest to an author or editor. For example, a paragraph is a single element at the logical level but it may be split across two pages at the final form or layout level.
SPDL describes document layout in device-independent terms, so that the same SPDL document description can be mapped into a variety of output devices, such as a low-resolution laser printer, a high- resolution laser printer, a microfiche recorder, or a display terminal. If an output device is unable to clearly render the pages as specified by SPDL, SPDL allows the user to select alternative rendering methods.
When a document is defined and marked up at the logical level using SGML, the formatting rules for converting it into final form can then be specified using the proposed DSSSL standard. SPDL can, in turn, be used to specify the output of DSSSL processing.
While waiting for the industry to produce mature applications that can interpret SPDL, DODIIS will use the PostScript (PS) and Encapsulated PostScript (EPS) from Adobe Systems Incorporated as an interim standard for interchange of composed document data. PS is a simple interpretative programming language with powerful graphics capabilities that has become a de facto industry standard. It is a high- level, device-independent language, on which SPDL is based. PS files are created, transmitted, and interpreted in the form of source text and there is no compiled or encoded form of this language. Similar to PS, EPS is a format for importing and exporting PS files among applications in a heterogeneous environment, to include or "encapsulate" a file in another PS language page description.
One prominent spreadsheet package, Lotus 1-2-3, has become heavily used, and as such, has established de facto file format standards. In particular, the WK1 format has become the de facto standard for storing spreadsheet data and is supported by many major spreadsheet vendors. Short of finding non-proprietary standards that address this area, the WK1 format will be considered acceptable for spreadsheet applications implemented within the DODIIS community as a gap filler.
DODIIS adopts FIPS PUB 161, Electronic Data Interchange(EDI), for electronic interchange of documents that are highly structured, usually consisting of a sequence of numeric or alphanumeric fields rather than free-form text. According to established rules and formats, EDI documents are converted to strictly formatted sequences of data elements and transmitted between computers. The strict formatting permits computer programs to assemble, disassemble, and understand the information.
Implementation of EDI requires a family of standards, including: 1) syntax standards that specify data organization, the character set for data, and the control characters that start, end, and separate data elements and other groupings within the transmitted data; 2) standards for envelopes that enable a communications protocol to carry and direct the data; 3) data element standards that specify data element types, and for some data elements, the list of data items permitted; 4) data segment standards that form meaningful groupings of data elements; and 5) standards for specific document types.
There are two widely-used families of standards: 1) U. S. domestic standards developed by ANSI X12; and 2) the international standards, called EDIFACT (EDI For Administration, Commerce, and Transport) which is developed by the United Nations Economic Commission for Europe, Working Party Four on Trade Facilitation (UN/ECE/WP4).
FIPS PUB 161 adopts X12 and EDIFACT, with specific conditions. FIPS PUB 161 is to be used in the DODIIS community if: 1) the data is to be transmitted electronically; and 2) X12 transaction sets or EDIFACT data meeting the data requirements of the interchange have been developed and approved under the conditions of FIPS PUB 161.
X12 and EDIFACT are separate, although similar, families of standards. Efforts are currently being made to align the standards, and the X12 committee is expected to adopt the EDIFACT syntax by 1997. FIPS PUB 161 will be updated to reflect X12 adoption of EDIFACT standards.
Standards in this component describe pictures, including both raster (bit) images and vector drawings.
For the interchange of raster graphics data, DODIIS applications are required to support the Tag Image File Format (TIFF) which was developed by Microsoft Corporation and Aldus Corporation. TIFF is a popular de facto standard, used by many image scanner vendors to store image data and by many commercial desktop publishing and word processor software developers to incorporate images into documents or publications. Printer manufacturers and facsimile vendors are also in the process of adopting the TIFF for their product lines.
While recognizing that TIFF is a proprietary format that comes in various flavors, thus causing compatibility problems, DODIIS will use TIFF for the interchange of raster graphics data as an interim measure, due to the lack of non-proprietary standards offering comparable capabilities.
Graphics Interchange Format (GIF) is a popular raster graphics file format developed by CompuServe that handles 8-bit color (256 colors) and uses the Limpel-Ziv Welch (LZW) method to achieve compression ratios of approximately 1.5:1 to 2:1. GIF is one of the most commonly used graphics formats on the Internet. As such, the DODIIS community is adopting GIF as a gap filler.
MIL-STD-28002, Requirements for Raster Graphics Representation in Binary Format, was adopted as a future standard in last year's DODIIS Profile but is being withdrawn at this time because DODIIS requirements for raster graphics data interchange are adequately met with TIFF, GIF, and International Telecommunications Union - Telecommunications Standardization Section (ITU-TSS) Groups 3/4. (Note that the former International Telegraph and Telephone Consultive Committee (CCITT) has recently been renamed to International Telecommunications Union - Telecommunications Standardization Section.)
The Computer Graphics Metafile (CGM), as defined in FIPS PUB 128, is adopted by DODIIS for the interchange of vector graphics data. Published on 16 March 1987, FIPS PUB 128 adopted ANSI X3.122- 1986, which is identical to ISO 8632:1987. The original CGM standards have been withdrawn and replaced with ANSI/ISO 8632:1992. The revised ANSI/ISO standard incorporates amendments to the original ISO standard to add a global symbol capability and improved engineering drawing capabilities such as better control over fine details of line drawings. Three-dimensional geometry extensions were not addressed at this time.
DODIIS will adopt the revised FIPS PUB 128-1, which is expected to be published soon. It is being aligned with the revised ANSI/ISO standard, with an added requirement to use CGM profiles specified in MIL-D-28003A for technical and publishing applications and a recommendation to use an application profile for other applications. MIL-D-28003A, along with its amendment, is the current Military Specification for the Computer-aided Acquisition and Logistic Support (CALS) CGM profile that defines the use of CGM for two-dimensional vector drawings or illustrations in technical publications.
For computer-aided design, DODIIS adopts the Initial Graphics Exchange Specification (IGES). FIPS PUB 177, Initial Graphics Exchange Specification (IGES), defines four application-specific subsets of IGES. This specification includes lists of allowable IGES entities, forms, and constraints dealing with the creation and translation from a native CAD format to a neutral IGES subset format. The four defined application subsets are:
The use of maps and the creation of entity symbology which overlays the map background display are particularly relevant to many intelligence activities. Several types of map products are available to support the variety of mapping applications within the community, including video maps, raster maps, and digital map files. Additionally, several organizations have generated symbol definitions that address the shape and content of entity symbology. The symbol definition standards being adopted within the DODIIS community are defined in the following documents: 1) North Atlantic Treaty Organization (NATO) Standardization Agreement (STANAG) 2019, Military Symbols for Land Based Systems; 2) Army Field Manual (FM) 101-5-1, Operational Terms and Symbols; and 3) MIL- STD-2525, Common Warfighting Symbology.
Because there are numerous commercial geographic information system (GIS) applications that satisfy command specific map manipulation and graphic overlay requirements, conformance with the DODIIS map graphics standards will not require the use of any particular GIS application or product. Conformance will, however, require the use of standard government distributed map products and the integration of standard symbol libraries. Additionally, to maximize the sharing of map graphic applications among the community, the map graphics software and supporting data should be implemented as a self contained, modular application with well defined inputs and outputs.
To promote the exchange of digital cartographic files and map generated graphic images within the DODIIS community, mapping systems must support common interchange formats. However, because there are currently no common formats in which all geographic and cartographic data products are distributed, it is necessary that present day mapping systems support numerous product specific distribution formats. To reduce the number of product specific formats that have to be supported, the Defense Mapping Agency (DMA) is in the process of standardizing on the storage and distribution format for much of its mapping, charting, and geodesy (MC& G) data. The current interchange formats, which are being adopted by DODIIS as map product interchange standards, are:
Those mapping applications that require national cartographic data (i.e., data which is distributed by the US Geological Survey [USGS]) should also support the two principal data interchange formats that are used by the USGS: the Spatial Data Transfer Standard (SDTS), defined in FIPS 173, and the Digital Line Graph-Level 3 (DLG-3) standard, defined in the USGS Standards for Digital Line Graphs.
Functional requirements form the basis for selecting the particular MC& G products that map systems must support. However, considering that there is a great deal of overlap in the overall community-wide map system functional requirements, and considering that it will often be necessary to exchange map information among community members, it is reasonable to expect that some products are essential. As such, several DMA products are being specified as required products that must be supported by all map system applications selected for use within the community. These products are:
Table 2-5 lists some other widely used map products currently available from government agencies such as the DMA, Central Intelligence Agency (CIA), National Geophysical Data Center (NGDC), and the USGS. Government distributed products such as these are optionally allowed to be used within DODIIS mapping system applications in situations where DMA products do not satisfy current functional requirements.
Table 2-5 . Map Products for Optional Use in Automated Systems
Standards in this component address formatting and compression of imagery data, which includes images and sub-images, and other information related to them, such as symbols, labels, and text, to facilitate sharing among networks of heterogeneous image processing workstations. It is also important to note that many products use intermediate data formats during the manipulation of image data. This practice is acceptable as long as the data is converted to a standard format after being manipulated.
The National Imagery Transmission Format Standard (NITFS) and all of its components (MIL-STD-188- 196, -197, -198, MIL-STD-2301, MIL-STD-2500, MIL-STD-2045-44500, MIL-HDBK-1300, and Joint Interoperability and Engineering Organization (JIEO) Circular 9008) should be used to format digital imagery and imagery-related products and exchange them within the DODIIS community. The NITFS is a suite of standards for data format, image compression algorithms, and communication protocols, as described below:
As the standard method for the compression and decompression of photographic images (still images), DODIIS adopts the Joint Photographic Experts Group (JPEG). JPEG is a joint effort by ISO (ISO 10918- 1) and ITU-TSS (ITU-TSS SGVIII) to define a common compression and encoding scheme for still- frame, continuous-tone (multi-level), gray-scale and color digitized images.
JPEG includes two basic compression methods, each with various modes of operation. A Discrete Cosine Transform (DCT)-based method is specified for "lossy" compression, and a predictive method for "lossless" compression. JPEG has the following four modes of operation:
Standards in this component address compression of full-motion video data for storage and transmission, interchange of video teleconferencing data over communication lines, and synchronization of video teleconferencing data. (Note: At this time, DODIIS is primarily addressing studio-based video teleconferencing; considerations regarding desktop video teleconferencing will be forthcoming.)
The Motion Picture Experts Group (MPEG) is adopted by the DODIIS for compression of full-motion color video and associated audio data. A joint-development project of ISO
(ISO 11172) and ITU-TSS, MPEG provides coded representation of video and audio for digital storage on media such as CD ROM, digital audio tape (DAT), Winchester disk and writable optical discs, and on communication channels such as Integrated Services Digital Network (ISDN) and local area networks (LANs).
MPEG provides the compression of video signals with a target transfer rate of about 1.5 Mbps at 30 frames per second (fps), and of a digital audio signal at the rates of 64, 128, and 192 Kbps per channel. It also deals with the synchronization and multiplexing of multiple compressed audio and video bit streams. The complex set of compression tools used in MPEG include JPEG for the intraframes, combination of predictive and interpolated interpolative coding techniques, and subband coding for audio.
Unlike JPEG, MPEG is designed specifically for video and takes an asymmetrical approach to compression, dividing the world of compressed videos into publishers-producers and consumers-viewers. Also, this specification does not define the exact procedure for compressing video the way that JPEG does for still images. It merely specifies the format and data rate of the output bit stream, as well as a set of compression techniques that can achieve varying degrees of quality.
DODIIS will monitor related activities on generic compression techniques for possible future inclusion into the DODIIS Profile.
The MPEG1 family of standards uses a combination of lossy and lossless compression techniques. MPEG1 was designed for non-interlaced video at transmission speeds as low as 1.5 Mbps. Because it does not support interlaced television displays, MPEG1 will be used mostly for CD-ROM and other computer-monitor applications.
MPEG2 (ISO/IEC 13818, Information Technology - Generic Coding of Moving Pictures and Associated Audio) was designed for interlaced video and transmission rates as high as 100 Mbps. MPEG2 is still evolving but appears to be the standard for HDTV in the U.S. The advantage of MPEG2 was the desired 25-1 compression ratio. The disadvantage is that both transmitter and receiver must calculate tens of millions of transcendental functions in real-time on the fly. The silicon technology to do all this is not quite there today and is bound to be expensive when it arrives, but chip makers are quickly fabricating special MPEG digital signal processors which they claim will be up to the task.
MPEG2 currently has three parts:
Six additional parts are planned including: Compliance (expected 11/95) which is designed to be an aid to both the customers and suppliers of MPEG2-based products to assist in determining if they meet standards specifications and insure interpretability amongst the many suppliers; and Extensions to parts 1,2, and 3 in the areas of a real-time interface, digital storage media command and control and additional audio and video specification.
Video Teleconferencing (VTC) is available principally through the use of a unit called a Coder/Decoder or CODEC, which digitizes motion video, accompanying audio, and still-frame video-camera graphics. These digitized images are compressed (encoded) and transmitted in almost real-time (usually less than a second) to the remote site where a second CODEC decodes the information back to an analog signal.
An international standard, ITU-TSS Recommendation H.261, guarantees that any CODECs manufactured according to the standard will be able to communicate with each other. H.261 is an interoperability specification that does not define all aspects of image coding and decoding, but rather addresses analog- to-digital conversion of data coming out of video cameras, and compression of digitized data for transmission over communication lines. H.261 is often called the px64 standard because the data rate on the communication channel is p times 64 Kbps, where p is an integer between 1 and 30. For p=1, a low- quality video signal for use in videophone can be transmitted over at 64 Kbps; if p=30, a high-quality video signal for teleconferencing can be transmitted over at 2 Mbps. (DODIIS is also investigating the applicability of expanding VTC standards to the ITU-TSS H.320 family of standards, which have been adopted as DOD standards for ensuring interoperability among all DOD VTC equipment.)
The HDTV Grand Alliance, an industry alliance, is expected to recommend an HDTV standard by August 1995. As of 1/94, proposed HDTV standards run in excess of 750 Mbps, over 8 times as much information as the conventional NTSC and over 6 times as much as PAL. However, the low bandwidth of broadcast television channels - at most 30 Mbps- demand at least a 25-to-1 compression ratio. Standard techniques, such as MPEG2, provide suitable compression ratios. Unfortunately, some of the high definition promised by HDTV must be blurred to achieve such high compression ratios.
Largely for historical reasons, different and incompatible ways of composing and transmitting a television signal have developed in different parts of the world. The DODIIS Profile adopts two of the most prominent standards, National Television System Committee (NTSC) and Phase Alternating Line (PAL), as both standards are used in different regions of the global DODIIS community. Consequently, CODECs must be able to translate between NTSC and PAL signals.
Audio is the medium encompassing all forms of information transmitted by sound. DODIIS adopts ADPCM and 8-bit µ-law as stop-gap measures, largely based on the strength of industry use.
Data interchange security services are used to verify and validate the integrity of specific types of data interchange. Data interchange security services include non-repudiation (proof of origin, proof of delivery), authentication (peer entity and data origin authentication), data integrity, and access control. Digital signatures will be a common security mechanism to provide data interchange security services (e.g., data integrity, non-repudiation).
The DODIIS standards for data interchange security services are closely coupled with those identified for network security services (see section 2.6.5 ). DODIIS security standards in this service area include the NIST Digital Signature Standard (DSS) (FIPS 186) and the NIST Secure Hash Standard (SHS) (FIPS 180). The NIST DSS defines a public key cryptographic system for generating and verifying digital signatures. The private key is randomly generated. Using this key and a mathematical process defined in the DSS standard, the public key is generated. The DSS is used with the SHS to generate and verify digital signatures. Digital signatures are used to detect unauthorized modifications to data and to authenticate the identity of the user who generates the signature. Additional security standards being monitored for potential inclusion include the ITU-TSS EDI security extensions.
Additional standards address security formats. DODIIS standards for security formats include the CMW label encodings format (DDS-2600-6216-91), the DODIIS Network Security for Information Interchange (DNSIX) Network Level Module (NLM) label format, the DNSIX Network Audit Trail Format, and FIPS 188, Standard Security Label for the Government Open Systems Interconnection Profile. Future standards being monitored include the MIL-STD Common Security Label initiative.
