When computer scientists talk about formal systems they use an anonymous and underspecified notation that literally has no name and no specific formal standard. I cannot point you to its web page because it doesn't have one.
Guy Steele has a talk about it wherein he coins the name "Computer Science Metanotation" (CSM) and talks about how it's used in practice. He calls it "The most popular programming language in computer science".
The most popular programming language in computer science has no compiler, interpreter, or complete specification. It is remarkably concise. It grew over decades; today, dozens of variations are in use. Its complexity has reached the point where it needs to be re-explained every time it is used—but too often it is not; instead, each variant is more or less taken for granted. This has led to ambiguities and inconsistencies. Much effort has been spent in hand-translating, in both directions, between this language and other languages that do have compilers, primarily for the purpose of implementing yet other languages.→ Guy Steele