EML

The original design of the Data Manager Library was somewhat vague in its support for querying data tables. After further discussion (Matt, Jing, Duane, and Mark Servilla), we think that allowing the calling application to pass in an ANSI SQL string would be too problematic because of the parsing requirements. The problems arise from needing to parse non-standard entity names into database table names, and non-standard attribute names into database field names. For example:

SELECT SPECIES NAME, SPECIES ID FROM SPECIES

means one thing from the perspective of entities and attributes, but something else from a database perspective, where "NAME" and "ID" would be interpreted as column aliases.

Instead, we will design a query class that the calling application can use to
construct its queries in a more structured way by setting various attributes of the query object. At some later point, we may also support queries in an XML format that could be mapped onto the query object by the Data Manager Library. This would facilitate passing queries between two or more processes (e.g. first from Morpho to Metacat, and then from Metacat to the Data Manager Library code).

The JDBC ResultSet object that is returned could also pose a problem, since it contains references to the database table field names, not the original attribute names. The calling application could get around this by restricting itself to accessing the fields by position rather than by name.