Copied the Firebird 5.0 Language Reference as a starting point:
Renamed files and references using fblangref50 to langref (new naming convention)
Where applicable, replaced references to Firebird 5.0 with Firebird 6.0
Documented SCHEMA DDL
Documented IF EXISTS/IF NOT EXISTS for DDL
Documented FORMAT clause of CAST
Documented OWNER clause of CREATE DATABASE
Removed page size 4096
Removed multi-file database syntax and descriptions
Documented CURRENT_SCHEMA and SET SEARCH_PATH
Documented RDB$GET_CONTEXT SYSTEM variables CLIENT_OS_USER, CLIENT_VERSION, CURRENT_SCHEMA, PAGES_ALLOCATED, PAGES_FREE, PAGES_USED, and SEARCH_PATH.
Added schema to DDL statement syntax
Documented optional COLUMN noise for ADD and DROP and optional RESTRICT for DROP in ALTER TABLE
Documented [ACTIVE | INACTIVE] for CREATE INDEX syntax
Documented GREATEST/LEAST
Documented range-based FOR
Removed incorrect mention of decimal point in FLOAT
Documented aggregate functions ANY_VALUE, BIN_AND_AGG, BIN_OR_AGG, BIT_XOR_AGG
Documented system package RDB$SQL
Documented that DECLARE VARIABLE can now use any expression as default
ACCESS_PATH in profiler tables/views changed to BLOB SUB_TYPE TEXT before Firebird 5.0 release
Documented ALTER FUNCTION of function options
Documented ALTER PROCEDURE and ALTER PACKAGE of SQL security options
Documented scalar functions BTRIM, LTRIM, RTRIM
Documented AUTO RELEASE TEMP BLOBID transaction option
Documented GEN_UUID version parameter
Documented COLLATE clause for ALTER DOMAIN
Documented table-valued functions UNLIST, GENERATE_SERIES
Documented VARCHAR/VARBINARY optional length
Removed note on configuring max identifier length
Documented WITHIN GROUP, LISTAGG, PERCENTILE_CONT, and PERCENTILE_DISC
Corrected documentation of RDB$FUNCTION_ARGUMENTS.RDB$ARGUMENT_MECHANISM and RDB$PROCEDURE_ARGUMENTS.RDB$PARAMETER_MECHANISM (#236)
Clarified RDB$NULL_FLAG descriptions (#237)
Documented RDB$RESET_CONTEXT() function