The APIB gateway provides an interface between a user's web browser and the APIB's data access services. This interface consists of a collection of CGI scripts implementing various data access services and an SGML-to-HTML translator for STEP as shown in Figure 1. Each CGI script answers a particular type of user request. The requests are issued by means of entering information in a form and pressing a button to submit the request. The CGI script triggered by the form issues a query to the APIB and, using the query result, generates a new HTML page to display to the user. The new HTML page typically contains another form soliciting user input. The sample user session in Section 3 depicts the relationship between forms, scripts, and the APIB.
Figure 1: Architecture of the APIB gateway.
The SGML-to-HTML translator is used to convert SGML-tagged data from the source documents in the APIB into HTML so they can be displayed in a web browser. The translation is only necessary for query results containing actual text from the APIB documents. If the query result does not contain an actual piece of the document (for example, the result could be a list of object names satisfying the query), then the CGI scripts generate HTML output without use of the translator. The bidirectional arrow between the CGI scripts and the APIB and the unidirectional arrows from the APIB to the translator and from the translator to the CGI scripts in Figure 1 indicate this conditional use of the translator.