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| Paper: |
Autojoin: A Simple Rule Based Query Service for Complex Databases |
| Volume: |
295, Astronomical Data Analysis Software and Systems XII |
| Page: |
287 |
| Authors: |
Gaffney, N. I.; Gardner, L.; Brandt, M. |
| Abstract: |
Most databases used today are no longer flat. While the power of using these more complex data stores is well known, construction of queries can be quite a complex task. Currently this often requires detailed knowledge of the database structure and schema. As we move towards a VO paradigm, users cannot be expected to know the structure of databases, but will need to query them. Databases will need to provide query engines to complete queries automatically given only what the user wants to have returned and any qualifications they place on the query. For years StarView, a database query and data retrieval tool for the Space Telescope Science Institute, relied on a complex third party LISP-based program (QUICK) to construct valid SQL queries for the one database it could query. This limited our ability to support StarView as we could not easily add new rules to the system without completely rebuilding the query engine. Furthermore, QUICK did not have the ability to create SQL that would join tables in different databases (but hosted on the same server). Finally, the cost of upgrading to a new version of QUICK was prohibitively high. Our solution was to develop a rather simple database table driven Perl CGI program which is able to take as its input a skeleton SQL program. This may come from a program or other web page. In the query only the SELECT and user qualified WHERE clause are specified; no FROM or WHERE clause join information is included. The service then returns a fully qualified and syntactically correct query for the host database SQL program that can be used to get the information the user needs. Thus, an additional layer of abstraction for dealing with databases is created, freeing the user from having to know how tables are related in the database. In this paper we discuss the design and algorithm used to make Autojoin work as well as discuss how, when combined with a robust and searchable description of all the fields that can be publicly queried in the database, it allows users to tailor their questions to the database with ease and a high rate of success. |
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