Network based tools come in many varieties. Searching engines, worms, robots and browsers are a few of the names associated with this growing class of information technology applications. In this chapter we will examine ways in which documents intended to reside on networks effect the roles one must play both as author and user of information.
Certain trade names and company products are mentioned in the text or identified in an illustration in order to adequately specify the experimental procedure and equipment used. In no case does such identification imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the products are necessarily the best available for the purpose. This work described was funded through U.S. Government and is not subject to copyright.
The entire concept of a document is becoming increasingly obsolete. The document as database on a network cries for a new term (in the best Ted Nelson style) the docubasenet. The docubasenet has characteristics common to documents and databases and yet is something different. Most documents are meant to be printed, on paper. The look of words the typography and layout is important. The design of a document and the relationship of the words to the illustrations by their arrangement serve to enhance the user interface of the document. A document pleasing to the eye will convey it's content better than a document that is visually difficult to read.
Databases, information containers, are made accessible via a myriad of techniques; forms, full-text queries and batch processes. The information in a database is useless without a mechanism to get to the data in useful ways.
The docubasenet is information organized in a structured way, like a database, presented to the user as a document which can be queried. Distribution of the docubasenet occurs via networks. The distributed nature of information available via wide area networks opens up a wide range of options, possibilities and problems.
The more open and widespread a network becomes, the more useful and problematic it becomes. Let's now examine the "Mother of all Networks," the Internet.
According to some O'Reilly marketing literature:
Internet In A Box is the first shrink-wrapped package to provide a total solution for PC users wanting to get on the Internet. Internet In A Box provides instant connectivity, a multimedia Windows interface, a full suite of applications, and the first interactive guide to the Internet. - A subscription to the Global Network Navigator (GNN), the first interactive guide to the vast information resources of the Internet (viewed using Mosaic). - Software: The Air Series of Internet-access tools, including Mosaic, electronic mail, Usenet news reader, drag-and-drop file transfer, and telnet. - Two books that clearly describe how to use these resources: "A Guide to Getting Started", and a special edition of Ed Krol's bestselling book, "The Whole Internet User's Guide & Catalog." As the bandwidth demands increase, simple, even high speed, modems become insufficient. Multimegabyte images and hundred megabyte videos demand higher capacity networks. The solution just might be ISDN, the Integrated Services Digital Network [ISDN]. ISDN seems to be the network solution of choice by the most ubiquitous network providers, the telephone companies. There are even companies starting to offer "ISDN on-ramps" to the Internet. PSI's InterRamp [PSI] starts at about $30/month for 64K baud access. While configurations vary a typical ISDN configuration is usually 128K baud for a ball-park cost of $100-150/month; not a trivial cost but much less than the costs of dedicated T1 lines.
The most highly touted security technique is public key encryption [KEY]. Public key encryption involves the use of two keys. One is public and known to everyone; the other is private and known only to the message sender. Various techniques using the keys enable digital signatures, document authentication, privacy and other security mechanisms.
prog <reg expr1> [<reg exp2>...]
prog is a keyword which means to find or search.A search of the "archie" database is performed with each <reg exp> (a regular expression) in turn, and any matches found are returned to the requestor. Note that multiple regular expressions may be placed on one line, in which case the results will be mailed back to you in one message. If you have multiple "prog" lines, then multiple messages will be returned, one for each line.
A friendlier user interface exists via the program xarchie. An X window system program, xarchie lets you interactively select the database sources and pose queries. xarchie returns the results of the query in a list with the most relevant items on the top of the list.
FIGURE 1. XARCHIE - the X Window System User Interface to archie
Users of archie simply send email requests containing the command prog using the syntax specified above to search for particular programs or documents of interest. Archie email sends a response, telling you where to go to find the item you requested.
An archie site runs a program that maintains the database by using anonymous ftp. The archie program that build and maintains the database checks the contents of several hundred archive sites over approximately 1 to 2 months. Several sites now run archie servers. Some sites allow interactive queries of the archie database via TELNET, eliminating the delay inherent in email.
The following overview (written in April 1991) is from the WAIS project leader Brewster Kahle:
The Wide Area Information Servers system is a set of products supplied by different vendors to help end-users find and retrieve information over networks. Thinking Machines, Apple Computer, and Dow Jones initially implemented such a system for use by business executives. These products are becoming more widely available from various companies.
FIGURE 2. XWAIS - the X Window System User Interface to WAIS, results of a query
What does WAIS do? Users on different platforms can access personal, company, and published information from one interface. The information can be anything: text, pictures, voice, or formatted documents. Since a single computer-to-computer protocol is used, information can be stored anywhere on different types of machines. Anyone can use this system since it uses natural language questions to find relevant documents. Relevant documents can be fed back to a server to refine the search. This avoids complicated query languages and vendor specific systems. Successful searches can be automatically run to alert the user when new information becomes available. How does WAIS work? The servers take a user's question and do their best to find relevant documents. The servers, at this point, do not "understand" the user's English language question, rather they try to find documents that contain those words and phrases and rank them based on heuristics. The user interfaces (clients) talk to the servers using an extension to a standard protocol Z39.50. Using a public standard allows vendors to compete with each other, while bypassing the usual proprietary protocol period that slows development. Thinking Machines is giving away an implementation of this standard to help vendors develop clients and servers. What WAIS servers exist? Even though the system is very new, there are already several servers: * Dow Jones is putting a server on their own DowVision network. This server contains the Wall Street Journal, Barons, and 450 magazines. This is a for-pay server. * Thinking Machines operates a Connection Machine on the internet for free use. The databases it supports are some patents, a collection of molecular biology abstracts, a cookbook, and the CIA World Factbook. * MIT supports a poetry server with a great deal of classical and modern poetry. Cosmic is serving descriptions of government software packages. The Library of Congress has plans to make their catalog available on the protocol. * Weather maps and forecasts are made available by Thinking Machines as a repackaging of existing information. * The "directory of servers" facility is operated by Thinking Machines so that new servers can be easily registered as either for-pay or for-free servers and users can find out about these services. How can I find out more about WAIS?
Contact Brewster Kahle for more information on the WAIS project, the Connection Machine WAIS system, or the free Mac, Unix Server, and X Window System interfaces. There is a mailing list that has weekly postings on progress and new releases; to subscribe send an email note to
wais-discussion-request@think.com.
Brewster Kahle
Project Leader Wide Area Information Servers
Brewster@Think.com
It is important to note that the communications to the WAIS servers are accomplished using the ANSI standard protocol for database retrieval applications, Z39.50. The decision to use a public standard is what makes this communications method truly open.
One way of locating information on the Internet is to use gopher servers. Gopher servers maintain collections of documents with the additional ability of full-text searching. The gopher protocol and concept are due to the effort of the people at the Microcomputer and Workstation Networks Research Center at the University of Minnesota. One of the appealing aspects of gopher is the simplicity with which it presents itself to the user. You, the user, are presented a "file system" just like any hierarchically organized file system, except that this file system covers all information known to the particular gopher server. It's a simple, elegant, and powerful approach.
In the case of an interaction with gopher servers, however, these directories may exist anywhere on the Internet. Furthermore, the user doesn't really care where the information is, as long as it's accessible in a timely manner.
Client systems through which a user "speaks" to the gopher server can have a number of user interfaces. One of the clients on UNIX systems is based on curses and will function on any terminal.
FIGURE 3. Typical Gopher menu
According to Mark McCahill member of the gopher development team:
The Internet Gopher is a distributed document delivery service. It allows a neophyte user to access various types of data residing on multiple hosts in a seamless fashion. This is accomplished by presenting the user a hierarchical arrangement of documents, a menu, and by using a client-server communications model. In addition to browsing through hierarchies of documents, gopher users can submit queries to gopher search servers. The search servers typically have full-text indexes for a set of gopher documents; the response to a query is a list of documents that matched the search criteria. Internet Gopher servers accept simple queries (sent over a TCP connection), and respond by sending the client a document or a list of documents. Since this is a distributed protocol there can be many servers... but the client software hides this fact from the user. We currently use this technology at the University of Minnesota to help support microcomputer users... a couple of gopher servers have 6000-7000 computer Q&A items that users can search for answers to their questions. In addition, there are also gopher servers with recipes and other fun stuff.
Q1: What is veronica? A1: Veronica is a service that maintains an index of titles of gopher items, and provides keyword searches of those titles. A veronica search originates with a user's request for a search, submitted via a gopher client. The result of a veronica search is a set of gopher-type data items, which is returned to the gopher client in the form of a gopher menu. The user can access any of the resultant data items by selecting from the returned menu. A veronica search typically searches the menus of hundreds of gopher servers, perhaps all the gopher servers that are to the Internet. At present, there are no "veronica clients" per se; veronica is accessed through normal gopher clients. Veronica is tightly integrated with the gopher protocol. The veronica service comprises two functions: 1). Harvesting menu data from gopher servers, and preparing it for se; 2). Offering searches of that database to gopher clients. These two functions are not necessarily provided by the same host computer. Most users and administrators of veronica search servers will not need to be concerned with the first phase of the process. Operators of veronica query-engines can obtain a prepared dataset for use with the query server. Veronica evolved as a solution to the problem of resource discovery in the rapidly-expanding gopher meta-burrow. At the University of Nevada, there was an outcry for an easy way to find gopher-based information without doing a menu-by-menu, site-by-site search.(1)
jughead head can act as a search engine on a prebuilt table that allows searching through menus, or can create a linear view of menu space. When running jughead you can specify what part of gopherspace you want search tables built or a linear view thereof. When running as a search engine, jughead listens out a port for a connection and a search string. The search string can contain the boolean operations "AND", "OR", and "NOT" between words. If no operator is specified between words, it is an implied "AND" operation. For example either: "University of utah" or "University AND of AND Utah" will yield all gopher entries with "university" and "of" and "utah" in the title. The case of the letters is irrelevant. Now suppose you enter the string: "university of utah NOT gopher" This will return the same information as the first search except for those entries containing the word "gopher".
A knowbot is a program or agent that, like worms, travels from site to site, although with a more artificial intelligence flavor usually following knowledge-based rules. Another term for a knowbot might be an autonomous agent. Clear distinction between these terms are currently not meaningful. In the context of this section, finding information, let's look at one particular knowbot and one worm.
FIGURE 4. Telnet interaction with CNRI Knowbot
The WebCrawler is a web robot, and is the first product of an experiment in information discovery on the Web. I wrote it because I could never find information when I wanted it, and because I don't have time to follow endless links. The WebCrawler has three different functions: It builds indices for documents it finds on the Web. The broad, content-based index is available for searching. It acts as an agent, searching for documents of particular interest to the user. In doing so, it draws upon the knowledge accumulated in its index, and some simple strategies to bias the search toward interesting material. In this sense, it is a lot like the Fish search, although it operates network-wide. It is a testbed for experimenting with Web search strategies. It's easy to plug in a new search strategy, or ask queries from afar, using a special protocol. In addition, the WebCrawler can answer some fun queries. Because it models the world using a flexible, OO approach, the actual graph structure of the Web is available for queries. This allows you, for instance, to find out which sites reference a particular page. It also lets me construct the Web Top 25 List, the list of the most frequently reference documents that the WebCrawler as found. How it Works The WebCrawler works by starting with a known set of documents (even if it is just one), identifying new places to explore by looking at the outbound links from that document, and then visiting those links. It is composed of three essential pieces: The search engine directs the search. In a breadth-first search, it is responsible for identifying new places to visit by looking at the oldest unvisited links from documents in the database. In the directed, find-me-what-I-want strategy, the search engine directs the search by finding the most relevant places to visit next. The database contains a list of all documents, both visited and unvisited, and an index on the content of visited documents. Each document points to a particular host, and, if visited, contains a list of pointers to other documents (links). "Agents" retrieve documents. They use CERN's WWW library to retrieve a specific URL, then returning that document to the database for indexing and storage. The WebCrawler typically runs with 5-10 agents at once. Being a Good Citizen The WebCrawler tries hard to be a good citizen. Its main approach involves the order in which it searches the Web. Some web robots have been known to operate in a depth-first fashion, retrieving file after file from a single site. This kind of traversal is bad. The WebCrawler searches the Web in a breadth-first fashion. When building its index of the Web, the WebCrawler will access a site at most a few times a day. When the WebCrawler is searching for something more specific, its search may narrow to a relevant set of documents at a particular site. When this happens, the WebCrawler limits its search speed to one document per minute, and sets a ceiling on the number of documents that can be retrieved from the host before query results are reported to the user. The WebCrawler also adopts several of the techniques mentioned in the Guidelines for Robot Writers. (4) Implementation Status The WebCrawler is written in C and Objective-C for NEXTSTEP. It uses the WWW library from CERN, with several changes to make automation easier. Whenever I feel comfortable about unleashing the WebCrawler, I'll make the source code available! bp@cs.washington.edu Brian Pinkerton
Mosaic and it's commercial clones, such as Netscape from Netscape Communications, offer end users a view of a compound document. Many items in the document contain links to other documents. These hypertext links allow the user to easily browse an entire collection of related documents. The documents are distributed and accessed throughout the Internet via the protocols supported by the World Wide Web. The net effect (pun intended) is to be able read compound documents with images and sounds with information dispersed over the network. Mosaic has become a usable front end to the Internet.
FIGURE 5. NCSA Mosaic and Mosaic Communication's Netscape
According to the WWW FAQ (Frequently Asked Questions) maintained by Thomas Boutell:
What are WWW, hypertext and hypermedia? WWW stands for "World Wide Web". The WWW project, started by CERN (the European Laboratory for Particle Physics), seeks to build a distributed hypermedia system. The advantage of hypertext is that in a hypertext document, if you want more information about a particular subject mentioned, you can usually "just click on it" to read further detail. In fact, documents can be and often are linked to other documents by completely different authors -- much like footnoting, but you can get the referenced document instantly! To access the web, you run a browser program. The browser reads documents, and can fetch documents from other sources. Information providers set up hypermedia servers which browsers can get documents from. The browsers can, in addition, access files by FTP, NNTP (the Internet news protocol), gopher and an ever-increasing range of other methods. On top of these, if the server has search capabilities, the browsers will permit searches of documents and databases. The documents that the browsers display are hypertext documents. Hypertext is text with pointers to other text. The browsers let you deal with the pointers in a transparent way -- select the pointer, and you are presented with the text that is pointed to. Hypermedia is a superset of hypertext -- it is any medium with pointers to other media. This means that browsers might not display a text file, but might display images or sound or animations. Mosaic is a WWW browser with hypermedia capabilities. Mosaic documents are a form of compound documents. The compound document a user manipulates is "authored" using the HyperText Markup Language (HTML) which is a specific Document Type Definition (DTD) of the Standard Generalized Markup Language (SGML). In short the WWW designers wisely chose not to invent yet another language technology and instead chose an existing standardized language. The developers of Mosaic used the rich foundation of WWW as a starting point. These types of collaborations are what makes an open Internet such a valuable resource.
In fact, the traditional SGML vendor community is jumping on the WWW as a new found market. Vendors are releasing SGML products specifically to support and aid the writing of HTML documents. The decision by WWW developers to use SGML as the foundation for WWW documents is one of the Web's great strengths.
FIGURE 6. SoftQuad's HoTMetaL HTML editor and corresponding Mosaic view of document
HoTMetaL runs on PCs and Sun workstations. In addition there exists a number of free-ware packages for PCs and Macintosh. SimpleHTML is a HyperCard based editor for the Mac.
On UNIX workstations there is also tkWWW, an authoring tool based on the tk toolkit for X windows.
One of the most common methods is to simply use a text editor to write HTML directly. This "Iron Man HTML" technique can be aided by some editors, for example emacs, which provides an HTML mode to take some of the tedium away. HTML documents are readable and editable, they just require a little learning.
<!DOCTYPE HTML SYSTEM "html.dtd"> <HTML><HEAD><TITLE>Open Virtual Reality Testbed</ TITLE></HEAD></HTML> <H1>Open Virtual Reality Testbed Home Page</H1> <A HREF="OVRTbrochure.pdf"><IMG SRC="ovrtlogo2G.gif"><IMG SRC="pdfLogo.gif" ALIGN="left" > PDF file of OVRT brochure</A> <HR> <P>FIGURE 7. An HTML fragment
An interesting authoring issue concerns the conformance of HTML files with the HTML DTD. Some authoring packages help force conformance and others let you get away with sloppy HTML. Most browsers do not bother to check for compliant HTML and simply do the best they can with the display. If you are concerned with interoperability then it will pay in the long run to be in conformance.
An alternative to native HTML authoring is to write documents using your favorite text-editor, word process or publishing system and then convert to HTML. A large number of conversion programs exist for just this purpose. For example the rtf2html program on UNIX platforms will convert documents in the RTF format into HTML. Similarly there are converters for latex and FrameMaker. All of these conversions mechanisms depend on a "properly" written original document. For example documents written in WordPerfect must use the style feature in order to successfully convert. Often conversion mechanism require some hand editing to touch up conversion errors.
Following this conversion type of authoring Microsoft is introducing an add-on module for MS Word which will output HTML and Interleaf is producing Cyberleaf a higher-end HTML authoring tool which can read in WordPerfect, Word RTF, FrameMaker MIF, Interleaf and ASCII formats.(5)
One particularly useful and freely available tool is the html-analyzer(6). Created by James Pitkow at the University of Colorado, it validates the html links. According to documentation accompanying the software the analyzer performs as follows:
Specifically, all.html files are processed to 1) validate the existence of anchors 2) check that all tags used have links associated with them throughout the database and 3) check for a one-to-one relation between links and tags. It is important to note that the validation process checks http & relative addressed links only.
One important issue associated with wide distribution of HTML documents derives from the loosely coupled nature of the WWW browser with various applications commonly known as helper applications. On all platforms, Mosaic launches another helper application when the user encounter an image file. The particular application launched is dependent on the particular MIME(7) type of the data, and is often dependent on the extension used for the file name. If, for example, the HTML document points to a JPEG(8) formatted image, the client machine must have an application capable of displaying JPEG images and Mosaic must be configured to launch that application upon links to JPEG images. This same scenario occurs for sound and video files.
Documents created on one machine should not contain absolute path names. Authors should be careful to use only links with relative address names to other files on the same server. In this way the entire hierarchy of HTML files can be moved as a unit without concern for renaming file path names inside the documents. In addition the relative names often must only be names in directories down from the current location. This is a security feature.
As for security, WWW servers and Mosaic present a whole range of security problems.(9) Some of the many security issues are authentication of requests and server, privacy of request and response. In particular one very useful capability is the ability to execute arbitrary programs through the server. The CGI (Common Gateway Interface) attempts to control how program execution occurs, but clearly security can be compromised.
The behavior and assumption used by one browser may be different from another resulting in documents that look different. One browser may automatically interpret a newline as a new paragraph and another may not.
In addition there is ongoing work on the URC, a Uniform Resource Citation. A URC will be a set of attribute/value pairs describing an object. Some of the attributes include author, publisher, date, and copyright status.
Internet Draft - CERN - Uniform Resource Locators (URL) A Unifying Syntax for the Expression of Names and addresses of Objects on the Network Abstract Many protocols and systems for document search and retrieval are currently in use, and many more protocols or refinements of existing protocols are to be expected in a field whose expansion is explosive. These systems are aiming to achieve global search and readership of documents across differing computing platforms, and despite a plethora of protocols and data formats. As protocols evolve, gateways can allow global access to remain possible. As data formats evolve, format conversion programs can preserve global access. There is one area, however, in which it is impractical to make conversions, and that is in the names and addresses used to identify objects. This is because names and addresses of objects are passed on in so many ways, from the backs of envelopes to hypertext objects, and may have a long life. A common feature of almost all the data models of past and proposed systems is something which can be mapped onto a concept of "object" and some kind of name, address, or identifier for that object. One can therefore define a set of name spaces in which these objects can be said to exist. Practical systems need to access and mix objects which are part of different existing and proposed systems. This paper discusses the requirements on a universal syntax which can be used to encapsulate a name in any registered name space. This will allow names in different spaces to be treated in a common way, even though names in different spaces have differing characteristics, as do the objects to which they refer. The universal syntax to objects available using existing protocols, and may be extended with technology. It makes a recommendation for a generic syntax, and for specific forms for "Uniform Resource Locators" (URLs)of objects accessible using existing Internet protocols. The syntax has been in widespread use by World-Wide Web software since 1990.
the URL of a file
ftp://ftp.uu.net/published/osys-today/urdrafts.tar.Z
and the URN for the same file could be:
URNg1
IANA:merit.edu:9283492.
In the URN, the IANA indicates that the following organization (merit.edu) has the authority to assign URN IDs and that the following number is the ID assigned by that organization.
Searching clients such as WAIS which use URN would return a list of URLs, one for each site containing the document. Over time sites may delete or add the document, but the URN would always return the most recent list of URLs.
Logical document structures are the components of a document such as chapters, sections, heading and paragraphs, which comprise the entire document. Instances of these logical document items are the document itself. For example the name <CHAP> might refer to all chapters, a structural item of a document, and "Chapter 3 - Web Feet" is a particular chapter.
The entire structure of a document is defined in a Document Type Definition (DTD) which is a kind of metalanguage. DTDs define the structure of documents in a rigorous formal manner. Once a DTD is defined authors can write documents which conform to the DTD. In the case of the WWW, authors create documents which conform to the HTML DTD. Applications do not necessary enforce conformance which often causes confusion as one person's document "worked just fine" and when viewed on another browser has problems. Indeed the HTML DTD did not, for a time, keep pace with HTML features.
The following comes from the Internet Draft of the IETF(15) specification:
Abstract(16) HTTP is a protocol with the lightness and speed necessary for a distributed collaborative hypermedia information system. It is a generic stateless object-oriented protocol, which may be used for many similar tasks such as name servers, and distributed object-oriented systems, by extending the commands, or "methods", used. A feature of HTTP is the negotiation of data representation, allowing systems to be built independently of the development of new advanced representations. One recent development is S-HTTP, the Commerce Net Secure HTTP Proposal.(17) According to a draft:
Secure HTTP has been designed to enable incorporation of various cryptographic message format standards into Web clients and servers, including, but not limited to, PKCS-7, PEM, and PGP. S-HTTP supports interoperation among a variety of implementations, and is backward compatible with HTTP. S-HTTP aware clients can talk to S-HTTP oblivious servers and vice-versa, although such transactions obviously would not use S-HTTP security features. S-HTTP does not require client-side public key certificates (or public keys), supporting a symmetric session key operation mode. This is significant because it means that spontaneous private transactions can occur without requiring individual users to have an established public key. While S-HTTP will be able to take advantage of ubiquitous certification infrastructures, its deployment does not require it. S-HTTP supports end-to-end secure transactions, in contrast with the existing de-facto HTTP authorization mechanisms which require the client to attempt access and be denied before the security mechanism is employed. Clients may be "primed" to initiate a secure transaction (typically using information supplied in an HTML anchor); this may be used to support encryption of fill-out forms, for example. With S-HTTP, no sensitive data need ever be sent over the network in the clear.
FIGURE 8. GNN home page and one major subdocument
FIGURE 9. NIST main home page and two laboratory home pages.
The development and implementation of a central NIST WWW page took a great deal of internal coordination. The main issues were not technical they were policy and enterprise organizational. The existing policy is to let each laboratory maintain its own web and to have the central web contain a pointer. This solves two problems: each laboratory wants to maintain and control its own information, and the organization responsible for central computing services does not have the resources to manage the entire institute's many and varied web servers. Each laboratory does however have an information "czar" responsible for ensuring the validity of the laboratories web information.
Often the problems associated with presenting and disseminating information via the WWW are not technical. They are procedural. Issues of responsibility and control often become stumbling blocks along the path toward new information infrastructures. The approach taken by NIST, that of centralizing a small access point and delegating other dissemination points, appears to be a workable solution for a reasonably large organization.
The Library of Congress is beginning to use the World Wide Web (WWW) to present information about and materials from its collections over the Internet. This project is in its infancy and will be developing over the next year. Some of the current LC WWW offerings include: photographic and sound collections from the American Memory Project, the African-American Culture and History on-line exhibit, Country Studies from the Federal Research Division, and access to LC MARVEL (LC's gopher-based campus-wide information system) and LOCIS (the Library of Congress Information System). In addition, the Library is developing a Global Electronic Library, which links to WWW meta indexes and search tools, federal government information, and eventually other WWW resources categorized by subject.
FIGURE 10. The U.S. Library of Congress home page and a photography collection page.
FIGURE 11. The Geometry Center and results of interaction with tiling program via Mosaic
In addition to some pretty pictures, the Geometry Center offers multimedia courseware via WWW. A tutorial and demonstration of four-dimensional geometry and the illustration of a 4D cube, a tesseract, are illustrated in the next figure.
FIGURE 12. Images from an interactive tutorial on 4 dimensional space
Much of the educational benefit of this on-line tutorial derives from the large number of MPEG (Motion Picture Experts Group format) animations. These animations take the user through a step-by-step development process. The motion illustrated by the animations is critical to an understanding of the concepts.
On-line documents also suffer from dependence on a viewer or other operating system capabilities. Once a document is printed it is always "usable." An on-line document must exist within the context of software and an operating system that also must function correctly. The archival quality of on-line documents is therefore bound to longevity of an unknown party such as the operating system or browser's vendor. If a vendor ceases to exist or ceases to support a critical feature of the operating system, the on-line document can become useless. This implies that along with the benefits of on-line documents, there are some risks.
The benefits of moving towards on-line network based distribution mechanisms do appear to be compelling enough to risk some problems. Let's now take a look back at the questions asked at beginning of the chapter.
What is a document in the context of electronic authoring and distribution?
Documents are changing entities. They depend on the environment and are often accompanied by multimedia information.
How can I find the information I want in the vast swamp of information on the net?
A wide variety of tools exists which enable searching. In fact there are too many tools. Archie, WAIS, Veronica and so on are all useful tools. Unfortunately, you must use the tools and learn about sites with rich indices that enable you to find relevant information. In short, roll up your sleeves and sweat a little, there is no magic incantation.
As an author, what can I do to make the information in my documents more usable and useful?
Probably the most useful advise is to structure your information logically. After an initial outline, use the structure-naming tools available in your word processor. Often these are called styles or tags. Documents with meaningful named styles and tags can usually be converted into meaningful logically marked-up documents which can be used and reused. Reuse is a key advantage of properly tagged documents. Information used as a paper document in one instance can be converted for CD-ROM use in another instance and for network browsing in another case.
When all is said and done the content is what usually matters most. However, networked multimedia documents are able to communicate information more effectively than dry information. It is the communication of ideas which ultimately determines the success or failure of any document.