SQL Server supports creating extended properties for objects in your schema. Extended properties are the equivalent of a property bag, allowing you to create as many key/value pairs as you like on schema objects. Tables, columns, views, procedures are some of the SQL objects supporting extended properties. Tables are the most likely candidate, in my mind, for the use of extended properties.
According to Technet, extended properties have been used for descriptions, formatting hints, validation definitions, presentation suggestions, and many other uses. https://technet.microsoft.com/en-us/library/ms190243(v=sql.105).aspx
Extended properties are easy to view from SQL Server Management Studio. You can create them in SSMS as well as view existing extended properties. There is a hierarchy to the extended properties. A column level property requires the identification of the table level property, which requires a schema level property.
I remember that many years ago PowerBuilder was a popular tool for creating windows database applications. It worked nicely with SQL Server, as well as with the Watcom database engine, shipping with the client tool. Either database utilized extended properties to support the GUI. Labels and captions of database views and columns were stored along with the column definitions. This was used to provide standard labels and captions when forms were created.
Are you using extended database properties? How have you found them to be useful? Why not leave a comment and get into the conversation?
Cheers,
Ben