to break backward compatibility. Little commercial incentive exists for vendors to make changing database suppliers easier (see vendor lock-in). Users evaluating database software tend to place other factors such as performance higher in their priorities than standards conformance. Standardization history SQL was adopted as a standard by the ANSI in 1986 as SQL-86 and the ISO in 1987. It is maintained by ISO/IEC JTC 1, Information technology, Subcommittee SC 32, Data management and interchange. Until 1996, the National Institute of Standards and Technology (NIST) data-management standards program certified SQL DBMS compliance with the SQL standard. Vendors now self-certify the compliance of their products. The original standard declared that the official pronunciation for "SQL" was an initialism: ("ess cue el"). Regardless, many English-speaking database professionals (including Donald Chamberlin himself) use the acronym-like pronunciation of ("sequel"), mirroring the language's prerelease development name, "SEQUEL". The SQL standard has gone through a number of revisions: Current standard The standard is commonly denoted by the pattern: ISO/IEC DIS 9075-n:yyyy Part n: title, or, as a shortcut, ISO/IEC 9075 (The term 'DIS' is not used in older versions). Interested parties may purchase the standards documents from ISO, IEC, or ANSI. Some old drafts are freely available. ISO/IEC 9075 is complemented by ISO/IEC 13249: SQL Multimedia and Application Packages and some Technical reports. Anatomy of SQL Standard The SQL standard is divided into 10 parts, but with gaps in the numbering due to the withdrawal of outdated parts. ISO/IEC 9075-1:2016 Part 1: Framework (SQL/Framework). It provides logical concepts. ISO/IEC 9075-2:2016 Part 2: Foundation (SQL/Foundation). It contains the most central elements of the language and consists of both mandatory and optional features. ISO/IEC 9075-3:2016 Part 3: Call-Level Interface (SQL/CLI). It defines interfacing components (structures, procedures, variable bindings) that can be used to execute SQL statements from applications written in Ada, C respectively C++, COBOL, Fortran, MUMPS, Pascal or PL/I. (For Java see part 10.) SQL/CLI is defined in such a way that SQL statements and SQL/CLI procedure calls are treated as separate from the calling application's source code. Open Database Connectivity is a well-known superset of SQL/CLI. This part of the standard consists solely of mandatory features. ISO/IEC 9075-4:2016 Part 4: Persistent stored modules (SQL/PSM). It standardizes procedural extensions for SQL, including flow of control, condition handling, statement condition signals and resignals, cursors and local variables, and assignment of expressions to variables and parameters. In addition, SQL/PSM formalizes