[xwiki-devs] SPAWN and external services

Hello, Sergiu criticized that a MathTran (a TeX-daeomon over the web) solution for formulae is bad because it relies on an external service or a complex installation... probably correct and the rest of his argument (in particular the wish for MathML) is more than valid! But, I realize that scientific documents, the goal of spawn, right?, are often made of external services. Consider the success of TeXmacs, one of the great features is its ability to connect to external systems, precisely. Typically, the following artifacts are sensible products of external services: - plots of functions - plots of data-sets - presentation of data-sets - advanced visualizations (e.g. chemical diagrams, construction plans, interactive geometry constructions...). I don't think we want all that to be solved internally in spawn, using external services is a must and, on a web-system, those should be web-services. In many cases, the XWiki source may contain info to regenerate fully the artifact (this is the case of many TeXmacs session I think), in other cases external interactions are needed. The service has to be running when authoring, for sure, but it should not need to when running. Or at least breakage of it should not impact viewers. That leads me to think that a good approach would be to store the products in a more managed way, e.g., as attachments, than in a cache where it can go away for size reasons. Comments welcome. paul