WorldCat : A global catalog : Quality control

OCLC takes seriously its stewardship of WorldCat: More than 27,000 libraries around the world depend on the quality of its records.
OCLC ensures quality by fostering and adopting international standards; conducting our own programs here and at member institutions; and participating in other quality programs.
OCLC quality programs
These efforts make WorldCat a precise reference by eliminating duplicate records and correcting errors through manual and automated means.
WorldCat change requestsAll cataloging member libraries help improve record quality by requesting changes to WorldCat and authority records through the following request forms:
Authority record change
WorldCat record change
WorldCat duplicate record merge
Minimal Level Upgrades and Database EnrichmentAll cataloging member libraries are able to assist in ensuring quality of WorldCat master records. Minimal-level upgrade capabilities allow these libraries to add and modify all editable fields of less-than-full-level master records, and upgrade them to full-level or less-than-full level status. Database enrichment capabilities let these libraries enhance master records by adding call numbers and subject headings in schemes not already present in a record; adding fields 006 (Fixed-length Data Elements—Additional Material Characteristics) and 007 (Physical Description Fixed Field); adding field 300 (Physical Description) to CIP records; and adding or editing field 505 (Contents notes).

المصدر
http://www.oclc.org/worldcat/catalog/quality/default.htm