This chapter examines standardisation activity on general information exchange and retrieval as it relates to Cultural Heritage On-line. By this we bring into this examination standards which may be used for the carriage of Cultural Heritage information.
Standards for general information interchange may be classified in the following manner:
This chapter therefore concentrates on application level standards. Application level standards specifically targeted at CHIO are dealt with in chapters 2 and 3.
The term Cultural Heritage Information On-line implies that the user accesses the information in an interactive fashion. However, there may be situations where bulk information exchange may be needed, for instance where, in a WEB situation, a large tree of pages may be downloaded for the user to browse off-line. For this reason bulk transfer standards are listed here as well as interactive standards.
Remote Database Access (RDA) is a protocol standard for accessing remote databases (ISO/IEC 9579-1:1993, https://www.iso.ch/cate/d17344.html). A specialisation of the standard allows the SQL query language to be used for accessing relational databases (ISO/IEC 9579-2:1993, https://www.iso.ch/cate/d17344.html) .
RDA is an infrastructure standard which is most likely to be used by a component of a distributed application that needs to access a remote database. For instance a WEB server back-end may be a distributed database.
RDA is an OSI protocol. However, the SQL Access Group has developed a mapping of the RDA protocol on to TCP/IP so that it can be used in an Internet environment. This is published by X/Open (X/Open J301). See https://www.rdg.opengroup.org/public/pubs/catalog/j301.htm
A further edition of RDA is under preparation where the distinction between the generic RDA protocol and the specialisation for SQL is removed. The new standard will provide direct support for the 1992 version of SQL only. There is work under way to extend SQL itself to allow storage and access to a multimedia database. This will include still images. The current working draft of ISO/IEC 13249-5 currently defines objects for GIF and JPEG but there is some concern about the proprietary nature of GIF (Compuserve) and this has yet to be resolved. Presumably RDA would then have to be extended to take care of this new work.
Bulk information transfer may be achieved by a file transfer protocol.
File Transfer, Access and Management (FTAM) is such a protocol (ISO/IEC 8571:1988 - second edition due). A number of profiles have been developed (ISP 10607-1 to 6). See https://www.iso.ch/liste/JTC1SC21.html for the ISO catalogue in this area.
FTAM is, however, not in widespread use. The Internet equivalent is the File Transfer Protocol (FTP), and although not having the extensive features of FTAM, it is in very widespread use. FTP, as defined in RFC 959 ftp://ds.internic.net/rfc/rfc959.txt and in a number of related RFCs, is one of the oldest and widely used protocols on the Internet.
Although the FTP specifications are old and stable, there is some current activity. The protocol's primary character set, 7 bit ASCII, has served the protocol well through the early growth years of the Internet. However, as the Internet becomes more global, there is a need to support character sets beyond 7 bit ASCII. There is a current Internet draft which examines the Internationalisation of FTP ftp://ietf.org/internet-drafts/draft-ietf-ftpext-intl-ftp-02.txt.
ETSI has been working on file transfer over ISDN and has recently published two ETS documents, ETS 300 383 which is an ETSI defined protocol (Eurofile), and ETS 300 388 which is a profile of FTAM. The ETSI web site is https://www.etsi.fr.
There are other publicly available specifications such as Zmodem and Kermit but these are disregarded here since they do not have the status of FTAM or FTP.
It should be noted that none of the bulk transfer mechanisms mentioned above have facilities for the protection of IPR nor for charging for content.
Messaging is an alternative way to exchange bulk information, but there are usually implementation limitations on the amount of exchanged information, usually around 2 mega-bytes.
There is an OSI based messaging system developed jointly by ISO and the ITU and this is specified in ISO/IEC 10021 and identically in the X.400 series of recommendations. To all intents and purposes, these standards are now complete and ongoing activity is of a maintenance nature. Profiles have been produced and these are found in ISPs 10611, 12062 and 12063. X.400 messaging has widespread implementation.
Internet Mail as specified in RFCs 821 ftp://ds.internic.net/rfc/rfc821.txt and 822 ftp://ds.internic.net/rfc/rfc822.txt is in widespread use as one of the oldest services on the Internet. Internet mail may not have the features of X.400 mail, but it is in much greater use. The MIME (Multipurpose Internet Mail Extensions) specified in RFCs 1521 ftp://ds.internic.net/rfc/rfc1521.txt and 1522 ftp://ds.internic.net /rfc/rfc1522.txt are a more recent addition to provide for non-ASCII information exchange. Further extensions to MIME continue to be developed. There two current Internet Drafts https://www.ietf.org/ids.by.wg/mhtml.html which are associated with the requirement to be able to send aggregate HTML documents between two mail user agents. There is a need not just to send and deliver such objects but also to display them taking into account embedded links.
It should be noted that mail systems do not have facilities for the protection of IPR nor for charging for content.
The X.500 (ISO/IEC 9594, https://www.iso.ch/liste/JTC1SC21.html Directory Service can provide a variety of database lookup services. The prime motivation for its development within the ITU was to provide a "white pages" directory to associate names with telephone numbers. ISO/IEC JTC1/SC21 collaborated with the ITU and could see more general application of the standard. The latest 1993 specifications are now considered to be reasonably complete. Activity is now concentrated on issues of deployment such as the EIDQ initiative. Apart from a "white pages" service, the users and providers of Cultural Heritage On-line could benefit from a more general database lookup service.
X.500 Directory Services are being implemented on the Internet and initially this will be used for a "white pages" service. There are several current Internet drafts associated with the X.500 Directory Service. In order to improve user access to the Directory, a lightweight directory access protocol ( LDAP) has been defined and there are a number of Internet drafts https://www.ietf.org/ids.by.wg/ids.html defining an infrastructure associated with the use of LDAP. The remaining Internet drafts concentrate on issues associated with the establishment of a "white pages" service and these again deal with infrastructure aspects.
The Domain Name Service (RFC 1034, ftp://ds.internic.net/rfc/rfc1034.txt is a central part of the Internet infrastructure. The primary service it offers is to deliver a numeric Internet address when presented with a domain name. The success and growth of the Internet has led to a lot of specification activity in relation to DNS. This is both to increase its operational efficiency (e.g. dynamic DNS update and negative caching) and to add functionality such as security mechanisms (e.g. secure dynamic update, authentication of updates and public key distribution). There is also clarification of existing specifications. There are several current Internet drafts all dating from the last third of 1996 https://www.ietf.org/ids.by.wg/dnsind.html. The proposed public key distribution services could be of interest when deploying security mechanisms in Cultural Heritage On-line.
There is some work going on in relation to Uniform Resource Names (URNs). A URN is a more persistent name for a document (or object) than a URL - it is location independent. There will be a need for a matching name resolution service and this could be supplied by an enhanced DNS service. The name resolution would result in a URL. See https://www.ietf.org/ids.by.wg/uri.html and https://www.ietf.org/ids.by.wg/urn.html
The use of the World Wide Web infrastructure is likely to be a key factor in the success of Cultural Heritage On-line. World Wide Web and associated standardisation is mainly carried out within the World Wide Web Consortium, otherwise known as W3C. This consortium is led by MIT in the USA and by INRIA in Europe. The standardisation effort is mainly concentrated on the HTTP protocol and the HTML mark-up language which is an application of SGML. Since HTTP makes use of MIME encapsulation there has been some extension of MIME as well. When mature, the standards are input to the IETF for publication as RFCs.
The Hypertext Mark-up Language is used to mark-up text documents in the Web environment. HTML V2.0 is published as RFC 1866 ftp://ds.internic.net/rfc/rfc1866.txt. It corresponds to the capabilities of HTML generally in use before 1994. HTML V3.0 was released in draft form but it suffered from a number of deficiencies and was considered at the time to be over complex. It was succeeded by HTML V3.2 https://www.w3.org/MarkUp/Wilbur/ in January 1997 which provided enhanced support for such features as tables, floating images, Java Applets and super/subscripts. There is a large amount of activity in the development of HTML. The multilingual extensions are discussed in chapter 5 in some detail as they are important to Cultural Heritage On-line. The applicability in this context of the remaining activity is not immediately obvious but for the sake of completeness, they are listed below.
To quote: "the Hypertext Transfer Protocol (HTTP) is an application-level protocol for distributed, collaborative, hypermedia information systems. It is a generic, stateless, object-oriented protocol which can be used for many tasks, such as name servers and distributed object management systems, through extension of its request methods. A feature of HTTP is the typing and negotiation of data representation, allowing systems to be built independently of the data being transferred."
Again, to quote: "the HTTP protocol is a request/response protocol. A client sends a request to the server in the form of a request method, URL, and protocol version, followed by a MIME-like message containing request modifiers, client information, and possible body content over a connection with a server. The server responds with a status line, including the message's protocol version and a success or error code, followed by a MIME-like message containing server information, entity meta-information, and possible entity-body content".
HTTP has been in use by the World-Wide Web global information initiative since 1990. HTTP V1.0 is specified in RFC1945 ftp://ds.internic.net/rfc/rfc1945.txt, HTTP V1.1 is new (Jan 1997) and is specified in RFC2068 ftp://ds.internic.net/rfc/rfc2068.txt.
The most significant change introduced by HTTP V1.1 is to simplify multi-homed Web Servers and conserve IP addresses. Older HTTP/1.0 clients assumed a one-to-one relationship of IP addresses and servers; there was no other established mechanism for distinguishing the intended server of a request than the IP address to which that request was directed. The changes will allow the Internet, once older HTTP clients are no longer common, to support multiple Web sites from a single IP address, greatly simplifying large operational Web servers, where allocation of many IP addresses to a single host has created serious problems. The Internet will also be able to recover the IP addresses that have been allocated for the sole purpose of allowing special-purpose domain names to be used in root-level HTTP URLs. Given the rate of growth of the Web, and the number of servers already deployed this is seen as an essential development.
Additions have included:
A number of Internet Drafts https://www.ietf.org/ids.by.wg/http.html. are in existence which clarify and add functionality to HTTP:
Transparent Content Negotiation is covered in chapter 5. However, perhaps the most significant of the remaining drafts is PEP. PEP will allow the agent and server to negotiate the use of non-standard extensions. Moreover, it will be possible to arrange for a download of code into the agent to support those extensions. This does have security implications for agents but presumably, the extensions code could take the form of JAVA applets thus invoking JAVA security functionality. These facilities will allow the openness of WEB protocols to be maintained whilst allowing new facilities to be tested within a standard HTTP environment. This of course does have an impact on standardisation. By allowing extensions to be negotiated and used within a standard and open HTTP environment, the new extensions can be used very quickly without the delays imposed by the formalities of standardisation. Once accepted by the market, the new facilities can be incorporated in the HTTP standard as and when convenient. This is quite important for Cultural Heritage On-Line since there are currently exciting developments in optimising the display of photographic images (see section 4.3.2).
This just gives a brief résumé of the various technical areas being examined by the W3C. (we need to decide which of these is of particular interest to Cultural Heritage On-line.) Web standards are changing rapidly. For right up to date information the reader should refer to https://www.w3.org. The summary information below was obtained from this Web site.
A style sheet describes how a document may be presented on a screen, in print, or perhaps how it may be pronounced. On the Web, content authors do not have the control over the colour, text indentation, positioning and other aspects of style as they do in the print medium. Similarly, a reader of such a document has no control over these aspects. A style sheet(s) attached or linked to an HTML Web document can allow an enabled browser to make the required representation.
In December 1996, W3C approved the Cascading Style Sheets level 1 (CSS1) specification as a full recommendation. Future W3C activity will be centred on extensions to CSS1. The CSS1 language is human readable and writable, and expresses style in common desktop publishing terminology. One of the fundamental features of CSS is that style sheets cascade; authors can attach a preferred style sheet, while the reader may have a personal style sheet to adjust for human or technological handicaps. The rules for resolving conflicts between different style sheets are defined in this specification.
Extensions to CSS1 include enhanced positioning controls, printing enhancements, handling of audio for speech synthesis applications, font handling etc.
Most Web browsers can handle a variety of Graphics formats. GIF and JPEG appear to be two of the more popular formats. However, there is still a need to make these more efficient due to the constraints on bandwidth. Another problem is that the more interesting options of JPEG are encumbered with patents rendering the standard less open and effective as it might be. This latter problem is being tackled by W3C which has published the Portable Network Graphics (PNG) specification which it is attempting to keep patent free. However, this is an area rich in activity within the supplier community and it is difficult for W3C to avoid the market forces in this area. Some exciting work is going on, for instance to optimise the efficiency of handling the zooming function. This area should be of particular interest to Cultural Heritage On-line activity. See also section 4.2.3.
As ISO/IEC 10646-1 gets applied on the Web, the issue of font support arises. Font support for HTML documents has been a little ad-hoc and a more organised approach is necessary and this is recognised by W3C. It has identified the following requirements:
The W3C position on this issue is that all its recommendations should meet or exceed established accessibility goals. W3C has established a disabilities page which has become a significant source of information on this topic. A briefing package is due to be published and this will describe a detailed plan for its future activity in this area.
W3C has recently launched a project (DSig) to establish two mechanisms, one for a signer to make statements about objects on the Web (signature labels) and secondly, for a user to interpret those statements with automated tools (trust management). The work will extend existing techniques to allow a signature to carry with it multiple assertions and to allow the data to be separate from the signature so that a signer may make assertions about data that he does not possess. This project will result in a proposed W3C recommendation, reference implementations for label writing and validation, a demonstration trust management system and a guide to using signature labels. It is hoped that this initiative will provide a solution to the problem of helping users to decide what to trust on the Web.
W3C and CommerceNet have been working on a negotiation and selection mechanism for the payment method to be used for a particular transaction from amongst a number that may be available. This project is known as the Joint Electronic Payment Initiative (JEPI) project.
PICS was an initiative closely associated with W3C and is an infrastructure for associating labels with Internet content. The infrastructure can be used with HTTP, FTP and Gopher but not with e-mail. The objective is to allow content to be classified so that, for instance, a filter mechanism can be employed to restrict access to unsuitable material for children. The infrastructure is flexible. Filters can be local to the client or elsewhere such as in a service provider. The labels may be embedded in an HTML document using the META tag or may be held by third party agencies which can associate labels with URLs. A browser can then interrogate the agency each time a URL is accessed. The infrastructure can also enable other label based techniques for e.g. code signing, privacy mechanisms and IPR management.
W3C is tracking this area carefully before making any development commitments. It has observed that the PICS infrastructure could meet the requirements of IPR management. W3C is planning a briefing package on IPR issues later in 1997.
There is always a stand-off between the public desire for privacy and the marketing need for information about a viewing audience. The use of the Web is no exception to this as it is increasingly used for marketing and sales purposes. W3C has held a workshop on demographic data collection and is a member of the Internet Privacy Working Group. However it is not actively working in this area. It will continue tracking this area and will produce a briefing package. Cultural Heritage institutions interested in marketing intelligence may well be interested in this activity.
Web security is a hot topic and there are many players one of which is W3C which has a working group. The IETF has a Web Transaction Security working group and there are a number of Internet drafts available. It is unclear at present whether a coherent, widely accepted security infrastructure will be developed for the Web.
There is a lot of activity in this area mostly outside W3C and there are a proliferation of methods for integrating OO protocols with HTTP. W3C organised a workshop with OMG in this area and is preparing a briefing package. See also section 3.4.5.
The deployment of efficient caching techniques in the Web are crucial to the scalability of the Web. There is a lot of activity in this area in terms of specification, research and prototyping. W3C appears to be acting in a coordination capacity rather than leading the action.
The current Web technology and Internet infrastructure are not very suitable for handling real time Audio/Visual streams. However, future Web technology and enhanced Internet infrastructure should overcome this. There is currently a lot of research work in this area and proprietary interest and the W3C is being encouraged to consider working in this area both as a coordinating influence and for the production of future standard specifications. See also sections 4.2.4 and 4.2.5.
HTML is a very simple application of SGML. Considerable increase in functionality would be possible if a more generic version of SGML could be handled by Web technology. W3C are active in this area and have already developed the XML specification which is still a simplified application of SGML but more feature rich that HTML and is suitable for Internet applications. Due shortly will be specifications for standard hypertext mechanisms to be used in XML. Specifications in the area of associated stylesheets are due by the end of 1997. This is relevant to CHIO and is mentioned in Chapter 2.