In commutative algebra, there seem to be two rather different notational conventions for ideals: either $I,J, \dots$ or $\mathfrak{a}, \mathfrak{b}, \dots$.
By itself, it is hardly surprising - after all, lots of other notations vary from source to source. I have, however, come across both conventions in a single script or article on many occasions. And the difference is rather striking: different letter is used, different case, different font...
I find this rather surprising and a little confusing, since usually a single convention is used within a piece of writing. I would very much appreciate any information on where such notational complication comes from. Is one of these conventions preferable (in some circumstances)?