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y<strong>in</strong>g, others also support extended operations like updates, <strong>in</strong>serts, or even create table operations.<br />

A good overview of exist<strong>in</strong>g products is given at<br />

http://cscsun1.larc.nasa.gov/~beowulf/db/exist<strong>in</strong>g_products.html. Further the collection at<br />

http://www.stars.com/Vlib/Providers/Database.html is recommended. Of course, we cannot<br />

discuss the different solutions here <strong>in</strong> detail.<br />

To give you a first impression two simple approaches are discussed. GSQL was one of the first<br />

(1993!) WWW-DB <strong>in</strong>terfaces that was developed. It is based on the CGI and is not very<br />

comfortable, but gives an idea how such an <strong>in</strong>terface works. The advantage of the CGI solution<br />

is the portability. Another simple but vendor specific solution is the mechanism provided<br />

by the (free) Internet In<strong>format</strong>ion Server of Microsoft for MS W<strong>in</strong>dows NT Server 3.51/4.0. It<br />

uses some k<strong>in</strong>d of server API (dynamic l<strong>in</strong>k libraries) and allows to access any ODBC database.<br />

4.3.1 GSQL<br />

Generic SQL (GSQL) [26] supports only query<strong>in</strong>g a database. It provides a form description<br />

with a so called proc file. In this proc file the appearance of the form for the user <strong>in</strong>put and the<br />

actions to be taken at submit are described. For Sybase as well as other databases a correspond<strong>in</strong>g<br />

backend is available. GSQL does two jobs:<br />

1) It generates a form for the user <strong>in</strong>put.<br />

2) From the <strong>in</strong>put it generates a SQL str<strong>in</strong>g accord<strong>in</strong>g to the given rules and forwards it.<br />

The CGI script just calls gsql with the proc file as parameter:<br />

In the follow<strong>in</strong>g proc file the user <strong>in</strong>terface and construction of a SQL str<strong>in</strong>g are described.<br />

There is pla<strong>in</strong> HTML which can be offered through the „TEXT“ element and there are Form<br />

elements which are related to the SQL str<strong>in</strong>g via the WHERELIST and SELECTLIST. All<br />

elements are expla<strong>in</strong>ed <strong>in</strong> the proc file <strong>in</strong> more detail. GSQL keywords have been written with<br />

bold letters. Figure 4 shows how the Forms <strong>in</strong>terface GSQL generates of this proc file looks<br />

like.<br />

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