Database schema confusion

I'm having a slight terminology meltdown as I design some classes. In Sql Server 2005, 'schema' refers to a namespace, and an organizational system for database objects. But for relational databases in general, 'schema' means the DDL design of tables, fields, etc. If I'm right about this, it explains a lot of the dissonance when I am trying to read microsoft documentation, and understand the various data access APIs. Can you explain what's going on here, is there really that much difference in the definition of 'schema'?

From stackoverflow

• You are correct. When in SQL 2005/2008, "schema" refers to a namespace, while in a relational database discussion "schema" would refer to the logical structure of the tables, views, procs, functions, etc.

  P a u l : This is also the answer, thanks.

• Yes, the word "schema" unfortunately has become overloaded among database vendors.

  "SQL-99 Complete, Really" says:

  An SQL Catalog is a named group of Schemas. ...

  An SQL Schema is a named group of SQL-data that is owned by a particular . ... Every Schema Object has a name that must be unique (among Objects of its name class) within the Schema it belongs to. The Schema Object name classes are:

  • Base tables and Views
  • Domains and UDTs
  • Constraints and Assertions
  • Character sets
  • Collations
  • Translations
  • Triggers
  • SQL-server Modules
  • SQL-invoked routines

  Oracle uses "schema" and "user" interchangeably, which always makes my eyebrows raise.

  MySQL uses SCHEMA as a synonym for DATABASE.

  PostgreSQL uses "schema" but uses "database" to refer to what standard SQL calls a "catalog."