The notability tag doesnt always mean the article in question is not notable I usually give my judgment on its notability in the edit comment  for the Ptolemy project I only said that the article did not assert its notability which it didnt it only had a link to the Berkeley page Ive heard of Ptolemy but I dont know much about it I got to the page by following the visual programming languages category If it isnt a programming language it probably shouldnt be tagged in a PL category Since Ptolemy is an academic project there should be notable academic sources that cover it I would count a paper with hundreds of citations to be a notable academic source Since you added a reference to such a paper I have no further qualms with the article with respect to notability   I have a couple of metrics in mind for establishing notability of programming languages First theres no question about popular languages If a language is popular it is probably also notable It shouldnt be hard to find secondary nonrandomblog sources discussing the language  So the problem then is how do we establish notability for nonpopular languages One way would be to find credible eg highly cited academic sources However many academic papers introduce languages to introduce or explain concepts I think in this case the novelty is more in the concept not the language and therefore discussion of the language should be a section of a Wikipedia article about the concept For instance in my research area functional reactive programming was introduced in a highly acclaimed best paper award highly cited paper That paper also discussed a domainspecific language called Fran Is Fran notable In my opinion no It is functional reactive programming that is notable and the article on FRP should discuss Fran Really they could have not given a name to Fran and the paper would have been just as good In other words languages are not necessarily notable because they implement notable concepts However if a highly cited paper was about the myriad design choices that led to the creation of a language that embodied those principles then I would say the language is notable If the paper is ABOUT the language then the citations reflect the languages influence on computer science   I think the corner case is where a language has no credible academic sources but is still notable SNOBOL is a good example It isnt popular in academia or in the mainstream but it was clearly a very influential language In this case we just need to make precise the ways in which it was influential on computer science Im not sure of any hard and fast criteria for doing this but Im open to suggestions  I dont think metrics such as code size or number of contributors is a good idea First of all an article created by someone else without my knowledge about my website was deleted when it is a collaborative project with hundreds involved  clearly there is precedent against this idea Second what would you actually write about a project with a large code base but isnt notable for other reasons All you could discuss is the project itself which isnt good enough in my opinion  we have to establish some continuity What influence does this project have on the rest of the world Why should anyone care For instance Factor programming language is a big project or so I hear but I wouldnt call it notable by any stretch of the imagination All of that source code could be deleted and nobody aside from the contributors would care very much sorry guys  I think it would also be a good idea to say what things DONT establish notability Here are some ideas   Relation to Google Just because Google was in some way involved doesnt make it notable The Factor page lists a tech talk given at Google as a source Who cares Google is huge  people talk there all the time people come up with nonnotable projects at Google all the time etc  Publication in an academic journalconference There are a lot of mediocre academic sources  A novel combination of language features If there isnt a reliable source to back this up its original research  Thanks for your comment