SQL is then used to extract the terms from the isolated documents, and to rank these terms to select terms for feedback. SQL statements then create new queries and allow for varying new term weights relative to the initial terms. The best number of documents for feedback term selection was between five and twenty, and the best number of terms from a list so generated between ten and twenty. Parallel efficiency, however, falls with a large number of processors since words are more likely to start with some letters than others and data is unevenly distributed. Balanced data storage results in better CPU times than would be predicted by processor increases.
Experts then select themes from the high-frequency phrases.
High-frequency phrases from the relevant set were ORed to the query and those from the nonrelevant set were combined using an AND NOT operation. Authors, journals, institutions, and countries concentrate in a few high contributors. Few papers were highly cited, and these tended to be recent . A code should state objectives, principles based upon these objectives, and rules oriented toward the objectives. Objectives are associated with orientedness toward identity, contents, bibliographic relationships, access conditions, provenance, consistency, and cost-effectiveness.