FYI: Z39.50 and the World Wide Web

Thu Feb 29 18:03:00 EST 1996

Through our work for the EC libraries programme "ARCA" project, we have
come face-to-face with some of the issues addressed in this discussion. We
have put together some initial thoughts on an integration path for Z39.50
and the WWW. More specifically, we have thought about what each of the
environments might stand to gain from a greater level of integration with
the other.

Comments and discussion are invited.

Z39.50 and the World Wide Web

Sebastian Hammer, Index Data
John Favaro, Intecs Sistemi

The tremendous success of the World Wide Web, and the increasing use
of WWW front-ends to library catalogs and other information systems
has caused decision- makers to question whether the investments
required to establish additional Z39.50 services are still warranted.
Meanwhile, the increased versatility of the 1995-version of the Z39.50
protocol - which enables it to provide powerful services outside of
the strictly bibliographic application domain - leads information
specialists to wonder where the WWW and Z39.50 fit together in the
evolving information infrastructure.

The Web as a Simple Networked Access System

Using the forms-based interface of the World Wide Web (WWW) in
conjunction with graphical clients or browsers such as Mosaic or
Netscape has become an inexpensive and popular method of providing
user-friendly access to on-line catalog systems. The tools required to
publish information on the WWW in this fashion are inexpensive or even
free, and are generally straightforward to use. The results are
rewarding: It is a remarkably simple task to produce attractive,
graphical interfaces which have similar appearances across many
different desktop platforms. No specialized software beyond a normal
WWW "browser" is required on the client side, and facilities for
File Transfer (FTP) and simple searching (WAIS, etc.) are
well-integrated into the WWW suite of protocols.

However, there are serious tradeoffs involved when using this
approach. The individual WWW client has no knowledge of the
application domain in which it operates. It receives a stream of
graphical user interface primitives (such as buttons, text-entry
fields, and formatted response data) from the server, and naively
displays these to the user. The WWW inherits a problem that has
haunted users since the first information systems went on-line using
simple character terminals: No two information systems share the same
interface characteristics. Each new system requires the user to master
a new interface structure, and, with the advent of graphical
interfaces such as the WWW, a new set of custom-designed icons and

Information systems often support the notion of a search "session", in
which the results of previous queries can be re-used or refined. The
HTTP (HyperText Transfer Protocol), which is at the core of the WWW,
is inherently stateless: Numerous problems arise when the interface is
adapted to host systems that have a notion of a continuous session
between the client (user) and the server. There are currently efforts
underway to add state-managing mechanisms to the underlying protocols,
but the basic paradigm remains essentially a stateless one, which fits
poorly with the session-oriented interfaces to most on-line
information systems.

Searching on the Internet - the Role of Z39.50

The Web is an ideal vehicle for organizations that are "vertically
integrated," that is, which are owners of content that they can
present to the user in a structure of their own choosing. That is why
many media and entertainment companies are showing a great interest in
the Web today. But when users must actively search the Web for
information across organizations, they encounter a sea of largely
unstructured data.

The library community has much to offer in the way of providing
structure to information resources on the Internet. The Z39.50
standard is a concrete representation of this fact. Currently the
search engines and indices of Web resources suffer from the same
weaknesses as the interfaces to library systems. No two are alike, and
there is no way to make structured use of the data that they return.
With the current growth of the Web, the search engines are becoming
increasingly important - a significant portion of the Web community
now spends more time looking at search engine output than on any other
type of Web page.   However, it may eventually become impossible for
any one organization to index it all in a useful way. We will need
more well-structured access methods to allow searching across multiple
indices. Here the power of Z39.50 as a true, mature information
retrieval protocol becomes evident.

The Z39.50 standard specifies an abstract information system with a
rich set of facilities for searching, retrieving records, browsing
term lists, etc. At the server side, this abstract system is mapped
onto the interface of whatever specific database management system is
being used. The communication taking place between the server and the
client application is precisely defined. The client application is
unaware of the implementation details of the software hiding behind
the network interface, and it can access any type of database through
the same, well-defined network protocol. On the client side, the
abstract information system is mapped back onto an interface which can
be tailored to the unique requirements of each user: a high-school
student may require a simple, graphical interface with limited
functionality, while an information specialist may need a complex,
highly configurable information retrieval engine. Finally, casual
users may prefer an interface which blends in smoothly with their word
processor, database software, or, indeed, WWW browser.

In summary, the essential power of Z39.50 is that it allows diverse
information resources to look and act the same to the individual user.
At the same time, it allows each information system to assume a
different interface for every user, perfectly suited to his or her
particular needs.

Navigation Between Resources - the Strength of the Web

Z39.50 was born as a point-to-point, client/server mechanism. It
provides very powerful means of locating records within one or more
databases on a single server.   The problem that remains is that of
navigation between servers or information resources:

o  How do we find the server and the database that has the information
we are looking for?

o  How do we learn about the contents of a server?

For learning about new servers or information providers, the Explain
facility of Z39.50 is an important resource. Explain provides a
structured mechanism for the information provider to publish
information about the capabilities of the server software, and about
the characteristics of the information stored in each database on the
server. The rich set of information elements defined by the Explain
facility includes contact information for the host instutution, as
well as specifications of the available access points (indices) for
searching. The rigid structuring of the information allows the client
software to automatically configure itself and adapt to each server
system, while the uniform interface to the descriptive information
about the database helps the user quickly orient himself to the
contents of a new information resource.

The truly difficult issue, however, is establishing an infrastructure
between servers that allow users to locate the right servers for their
purpose in an easy way. The Z39.50 URLs are useful in this respect,
because they make Z39.50 servers appear to be "just another kind of
document" in the Internet space. People can collect and categorize
collections of servers the same way they do other kinds of documents
or information resources. WWW search engines can even be used to
discover new Z39.50 servers.

Our preferred approach would be to use Z39.50 itself to find Z39.50
servers. That is what locator services can do. GILS defines an
application profile for Z39.50 that is useful for locating information
resources (although admittedly, GILS is optimized for US government
documents, and as such it is probably less than ideal for some other
purposes). These documents can be anything - from books to reports to
archives of photographs to on-line databases to WWW-documents (and
since a WWW-document can be a Z39.50 server, the locator service can
be used for exactly the purpose we have in mind).

With a slightly simpler and more general profile than GILS, Z39.50
could become a very powerful tool for accessing indices of information
resources. In effect, we are postulating that we replace or supplement
all of the existing WWW-crawlers with Z39.50 servers. In that way, we
would be able to access all of the different indices with a uniform
interface, and because the access structure is fully standardized, it
would be simple to gateway or replicate information between servers -
we would potentially only need a single starting point to search for
any kind of information anywhere in the world. Indeed, this is an
important part of the vision behind the Global Information Locator
Service currently being investigated by the G-7 Group of industrial

Again, static documents containing Z39.50 URLs will provide an
increasingly important means of discovering and accessing information
resources, as WWW- browsers with Z39.50 client-capabilities become
commonplace. When these documents are, themselves, served or located
by Z39.50-aware systems, the circle is complete.

In summary, we believe that there is a strong potential for a
profitable and synergetic relationship between the WWW and Z39.50. We
see the two worlds merging together, with each one growing stronger by
using the best elements of the other: Hyperlinks between systems and
document types from the WWW - structured searching and document
discovery from Z39.50.

Sebastian Hammer         [quinn at]             Index Data
Ph.: +45 3536 3672     <URL:>   Fax: +45 3536 0449

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