This chapter examines the representative international standards that relate to the museum interchange applications introduced in Chapter III. It examines how specific standards differ in capabilities or approaches but is intended to be as simple and nontechnical as possible without being misleading; readings listed in the bibliography provide more technical detail.
The CIMI Committee recognized that standards for interchange of museum information should result from adoption of existing standards whenever possible since museums had neither the technical expertise nor marketplace clout to develop de facto standards for any part of the interchange except data content.
Options for Telecommunications and Media Standards
The first area explored by the CIMI committee was what CIMI referred to as "lower level" communications and media standards. The museum community need not invent any ISO level 1-4 or their equivalent standards to support interchange of its data. Included in this are the CCITT X.25 series for packet-switched networks, CCITT I series for ISDN, TCP/IP for Internet, the IEEE 802 series for Local Area Networks, ANSI X.3 for FDDI (Fiber Distributed Data Interface), RS-232 and CCITT V series for modems and other media formatting standards such as ISO 9660 for CD-ROM.
+----------------------------------------------------------------------------+ | | | | | Packet Switched Networks CCITT X.25 | | | | ISDN CCITT I series | | | | Internet TCP/IP | | | | LANS IEEE 802 series | | | | FDDI ANSI X.3 148, 149 | | | | Modems CCITT V series | | | | CD-ROM ISO 9660 | | | | | +----------------------------------------------------------------------------+ Figure 13: Lower Layer Telecommunications, Media, or Network Standards
CIMI also concluded that underlying data representation standards such as ASCII, CCITT Group 3 and 4 facsimile, JPEG, MHEG, CGM ,TIFF, and CD Audio should be followed by museums regardless of the interchange application. It recognizes, however, that while the framework can sound definitive on this issue, concrete recommendations are often difficult to formulate because standards, especially in the area of video compression, are undergoing rapid development and implementations are lagging behind the adoption of new standards.
Options for Museum Interchange Applications
Figure 14 shows the standards that support each of the functional areas. Each of these standards supports one or more of the museum applications in the areas of business and curatorial information interchange involving textual and multimedia information, scientific measurements, citations and business obligations. Of course not all interchange applications pertain to all museum applications and in some cases a technical protocol or standard may support more than one interchange application. It is also the case that more than one interchange application will be necessary to support a particular museum application.
Data representation and data content and value (the structure and meaning of the data) standards have not been included in Figure 14. They both play an essential role in successful interchange but have to be defined separately from the standards that support interchange.
+----------------------------------------------------------------------------+ | | | | | InterchangeFunctions SupportingStandards | | | | Database Building ISO 2709, ISO 8824,25 ASN.1, ISO 8879 | | SGML | | | | Information Retrieval ISO 10162/63 Information Retrieval, | | ISO 9579-1 RDA, ISO 9579-2 SQL for RDA, | | ISO 9594/X.500 Directory | | | | Business Transactions ANSI X.12 EDI, ISO 9735 EDIFACT, ISO | | 10021/CCITT X.400 Message Handling, ISO | | 10160/10161 Interlibrary Loan | | | | Message Handling ISO 9594/X.500 Directory, ISO 10021/CCITT | | X.400, ISO 9735 EDIFACT | | | | File transfer ISO 8571-74 FTAM, FTP, XMODEM, KERMIT | | | | Document handling ISO 8613 ODA/ODIF, ISO 8879 SGML, | | | | Real-Time Links ISO 9040,41 Virtual Terminal ISO 8648, | | 8348, 8072 | | | | | +----------------------------------------------------------------------------+ Figure 14: Conventions and Standards supporting Interchange
The CIMI Committee first looked at interchange standards for database building that support the creation of Collections Catalogues and Reference Databases.
Collections Catalogues and Reference Databases
CIMI identified three approaches to interchange of database records for construction of shared catalogues, reference databases and authority files: ISO 2709 (Information Interchange), ISO 8824 (ASN.1) and its Basic Encoding Rules (ISO 8825), and ISO 8879 (SGML).
The CIMI Committee requested an analysis of the three options to support the building of collections catalogues and reference databases which addressed the following specific issues:
The Committee concluded that each set of standards had strengths and weaknesses and that these might warrant different decisions by museums in interchange of different types of data and for different purposes. To assist its review, the CIMI Committee had experts illustrate the way that museum records would be interchanged using each of the three standards and provide their views on the suitability of each. A summary of their positions and assessment of the conclusions museums can reach from them is presented below. The details are available in the CIMI briefing paper "Options for Computer Interchange of Museum Information (Perkins 1992).
ISO 2709-1981/ANSI Z39.2-1985
ANSI Z39.2 is the USA equivalent to ISO 2709 which is used hereafter. A more detailed description of ISO 2709 is found in Appendix A.
ISO 2709 is a content-independent specification of fielded text for data exchange. Its primary advantage is that it is widely used by libraries, archives and visual resource collections worldwide. A large market of commercial software has developed capabilities to import and export data in this form. A secondary advantage is that the record structure is simple for humans to understand. A disadvantage is that the ISO 2709 protocol has length limits and data representation restrictions stated within the standard itself or defined in existing implementations. Another disadvantage is that the process for defining content standards involves cooperating with either the relatively elaborate maintenance framework established by the library community or maintaining a parallel content standards maintenance function because fields cannot have more than one meaning. Other disadvantages are; existing parsers have been developed to read MARC records (an specific implementation of ISO 2709) not generalized ISO 2709; and, ISO 2709 does not allow the creation of an envelope into which other content may be placed so it cannot encapsulate data in formats other than its own, though it may point to them.
Museums should use MARC fields and AACRII content rules for bibliographic citations within other databases to facilitate linking. Museums will also want to consider related content designations such as UNISIST for abstracting and indexing or TEI Bibliographic control structures for descriptions of machine-readable texts. While these three are not seamlessly compatible there are similarities. Perhaps interest by museums will help convergence and harmonization to occur.
Museums should also consider ISO 2709 for interchange of data regarding collections of books, archives, and visual materials such as architectural drawings for which content standards are well developed within MARC and for which links can be made to materials held by institutions other than museums. Exceptions to this might be if the content model was represented in a way different from MARC (eg if the data content model developed by the Foundation for Documents on Architecture was implemented) or if the content as represented by MARC fields was expressed in another format such as SGML/SDIF for interchange.
ISO 8879 SGML
SGML, and its associated standards HyTime (ISO 10744), and SGML Data Interchange Format (ISO 9069 SDIF), are methods to denote the structure of free, fielded, or formatted text and to link these with associated images and sounds. The strength of the SGML-based standards is that they permit logical content designation of any data, including data represented in other standards, and can specify specific physical presentations of that data as well. An advantage is that SGML is implemented, especially in the publishing community and in the scholarly community which has developed the Text Encoding Initiative, and is being adopted more widely as a consequence of the support it received as part of the CALS standards suite. ISO 2709 data can be expressed in SGML and SGML can encapsulate other data and be interchanged in SDIF or within another communication protocol such as X.400. The registry of a new Document Type Definition (DTD) for SGML does not require reopening a standards process. Another benefit of SGML is that software to search data marked in SGML exists so that SGML encoded files can immediately be navigated as hypertexts. A disadvantage is that SGML parsers, while inexpensive, are a specialized application rather than being embedded, as they may soon be, in word processors or DBMS systems.
Museums should use SGML for most object description, especially if it involves use of extended text in fields in which the contents within text should be identified or if it involves text associated with graphics, images, sounds or multimedia, or if the ultimate purposes of the interchange will involve paper of electronic publishing.
Abstract Syntax Notation One (ISO 8824/5 ASN.1)
Together ISO 8874 (ASN.1) and ISO 8875 (the associated Basic Encoding Rules), is a mechanism for describing any data content in OSI. These are described in more detail in Appendix.
Among its advantages are that ASN.1 is the preferred OSI language for representing other protocols and standards. For example, ISO 8879 SGML, ISO 10161/62 Information Retrieval, and MHEG CD 13522 all use ASN.1 for encoding the formats. Because of its adoption in the OSI world ASN.1 utilities can be found for almost any platform and may be "present" in many systems at some level already.
Its strength lies in the ability to carry any kind of data, in any quantities and to maintain data relationships. A drawback is that implementing ASN.1 interchange, even using available utilities, is a highly complex technical task. ASN.1 parsers and utilities are readily available but involve complex coding and need significant technical expertise to use.
While ASN.1 can be used to encode data that is formatted for interchange according to other standards such as SGML/SDIF, it is also possible to use it directly for both formatting and encoding. The emerging MHEG standard for example strongly suggests this approach. For museums it appears appropriate for archaeometric or scientific data sets, especially if these contain floating point data, quantities of raw data types, or one-off interchanges for which the effort of developing external content agreements would be inappropriate.
The suite of technical standards for search and retrieval which were developed as NISO Z39.50 and have since been adopted as ISO 10162/10163 are considered the most promising way for searching remote systems running diverse software. Originally implemented by the library community for catalog searching, it has recently been endorsed by the Coalition for Networked Information (CNI) as a foundation standard for CNI's information retrieval systems. The proposal for CIMI to adopt ISO 10162/63 was based largely on its acceptance in the information network community (Lynch 1990).
It is important to distinguish between Information Retrieval functions of ISO 10162/63 and the database management functions of Structured Query Language (SQL) and Remote Database Access (RDA) extensions to SQL specified as ISO 9579 RDA. ISO 10162/10163 (Z39.50) especially is preferred for information retrieval services where knowledge, or data in context is wanted. For example, ISO 10162/63 allows searches for concepts like "Author" or "Title" to be conducted independent of the way data is represented internally in the application, or whether it is stored as a flat file or relational table. SQL and RDA extensions are designed for performing database management services such as updating, archiving, or moving databases, for query of relational tables, or for distributed database applications.
It was evident to CIMI that the future of forms-based, obligation creating, business transactions lies with EDI (Electronic Document Interchange) and that museums therefore should use EDI-based approaches to interchange of business transactions data when it is economically viable. Unfortunately, EDI is still represented by two competing, and as yet incompatible, standards: ASC X12 or ISO 9735 (EDIFACT). The use of ASC X12 is largely limited to North America but for museums which are located in North America, the option of adopting a more broadly accepted EDI standard is more illusory than real because the networks which handle EDI traffic define the protocols they will handle. Because bridges do exist to pass X.12 messages to EDIFACT networks and back, the museum community should adopt the EDI standards which will effectively carry messages in their country and develop translations, if necessary, between the representations used in the two protocols until the larger standards community can bring the competing approaches into harmony.
EDI implementations are becoming practical for smaller businesses as the cost of developing and implementing registered transaction sets drops, however it is likely to be the case for a considerable time that EDI messaging between major players in the museum community will have to cohabit with paper based transactions. Eventually it is anticipated that EDI will be available as ubiquitously as electronic mail; ISO is working on a proposal to provide interoperability through OSI which should speed the spread of EDI (Fincher 1990).
Messaging and Directory Services
The internationally accepted standards for communications, message handling, and Directory Services are X.400 and X.500. These are commonly referred to by their CCITT X. designation but have ISO standard numbers as well. X.400 is a suite of recommendations encompassing ISO 8505, 8883, and 9065; X.500 is ISO 9594.
X.400 one of the first OSI application layer standards to gain almost universal acceptance. Besides its use as the foundation for electronic mail it can carry messages with content defined by other standards, including EDI business transactions, electronic funds transfer, fax transmission, voice communications, and complex office documents containing both text and graphics (Swain and Tallim, 1990). X.500 is rapidly gaining acceptance as the way to specify the electronic address of people and organizations.
File transfer and directory services are successfully standardized in ISO 8571 File Transfer, Access, and Management (FTAM) and CCITT X.550/ISO 9594 OSI Directory standards. FTAM's advantage is that it has been implemented widely in the OSI world and supports extensive file transfer facilities, but its relationship to other file transfer methods in common use such as XMODEM and FTP needs to be explored. Museums should adopt systems which support these standards comprehensively.
Museum business documents ranging from business letters to publications are identical to those produced in other sectors, and standards developed there will work for museum needs too. Content standards governing some specific types of documents, such as catalogues raissonne, may prove valuable for museums if they wish to collectively author them. If content standards are followed, the documents will be made interchangeable if common markup conventions are adopted by the community. Beyond markup, which is taken care of by SGML (Standard Generalized Markup Language) interchange will be accommodated when (and to the extent that) the OSI Office Document Architecture and Office Document Interchange Format (ISO 8613 ODA/ODIF) are implemented. ODA attaches codes to a document so they can be converted to a common format (ODIF) for exchange with another system. Unfortunately, the ODA/ODIF standards have not yet been widely implemented so it is not practical yet to advise museums to use them, but it is clear that the underlying requirements of museums in this area will be adequately satisfied by generally adopted approaches, leaving only the content specification of particular types of documents as a museum-specific standards issue to be dealt with by markup conventions.
Museum requirements for human/machine and machine to machine interaction in real-time are common to those of other application arena's and fully satisfied by lower layer OSI protocols and ISO 9040/9041 Virtual Terminal standard which allows remote, realtime terminal control.
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