In relational databases, the information schema is an ANSI standard set of read-only views which provide information about all of the tables, views, columns, and procedures in a database. 

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It should be like the ultimate generic implementation of the AttributeTable pattern, with power not only to query, but to create tables, views, indexes, stored procedures, users, custom datatypes, etc. But in practice because of complete lack of support by most sql database implementations (and lack of support for many modern database objects and datatypes) is only a sorry shadow of what it could be.
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My experience is that vendors have been slow to (properly) implement such standards. Maybe in 5 or 10 years it will be more usable than proprietary ones.
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One thing I find funny is that while ObjectRelationalMapper proponents have created APIs to wrap a sql databases an make them work as closely as possible to a ODBMS, almost nobody (AlphoraDataphor is a notable exception,) has tried to create a relational wrapper on top of sql pseudo relational databases (TrueRelationalToPseudoRelationalMapping).

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See also SqlFlaws