The majority of the databases searched by the Library of Texas RDS are made available by their vendors via Z39.50. However, a small number do not provide this interface, but must nevertheless be integrated into the system.
Rather than increase the complexity of the RDS itself by adding code to give it the ability to search databases by non-Z39.50 protocols, a gateway approach was taken. Separate, free-standing gateway programs were written for each of the non-Z39.50 protocols requiring support.
These gateways function both as Z39.50 servers and as clients using some other protocol. Each gateway accepts Z39.50 search and retrieval requests, translates them into the appropriate back-end protocol, passes the requests through to the back-end server, fetches the results, translates them back into Z39.50 format and returns them to the Z39.50 client that originally issued the request. Thus, to the RDS, each gateway appears to be nothing more than a typical Z39.50 server, and no special-case code is required in the central system.
At present, two classes of non-Z39.50 database are included in the RDS. Four databases are supplied using Gale's proprietary XML-over-HTTP protocol, HITS; and two more by querying human-oriented web-sites and parsing the resulting pages. The databases supported in this way are as follows:
Table 5-1. Non-Z39.50 Databases in the LOT RDS
| Database name | Vendor | Access Method | Z39.50 DB Name |
|---|---|---|---|
| Biography & Genealogy Master Index | Gale | HITS | BGMI |
| Student Resource Center GOLD | Gale | HITS | SRCG/SRC1 |
| Texas Almanac | Gale | HITS | GTXS |
| What Do I Read Next? | Gale | HITS | WDRN |
| STAT!Ref | STAT!Ref | Web Interface | statref |
| Heritage Quest | ProQuest | Web Interface | hq |
We will now describe each of these databases in more detail.