title: Where is Ruby's ERB format "officially" defined?
body: <p>A number of sources (e.g. <a href="https://stackoverflow.com/questions/4284421/what-is-the-meaning-of-erb">What is the meaning of erb?</a> and three out of the top four results from <a href="https://www.google.com/search?q=erb+ruby+format&amp;rlz=1C5CHFA_enUS553US553&amp;oq=erb+ruby+format&amp;aqs=chrome..69i57j0l2.2268j0j7&amp;sourceid=chrome&amp;espv=210&amp;es_sm=91&amp;ie=UTF-8" rel="nofollow noreferrer">this google search</a>) cite <a href="http://ruby-doc.org/stdlib-1.8.7/libdoc/erb/rdoc/ERB.html" rel="nofollow noreferrer">http://ruby-doc.org/stdlib-1.8.7/libdoc/erb/rdoc/ERB.html</a> as the official documentation on the ERB format, but that really just gives you the API rather than the file format.</p>
  
  <p>I found a nice little summary in <a href="http://docs.puppetlabs.com/guides/templating.html#erb-template-syntax" rel="nofollow noreferrer">http://docs.puppetlabs.com/guides/templating.html#erb-template-syntax</a>, but there's got to be something more official, right? And who is the "defining authority"? Did this come out of Rails?</p>
  
  <p>Since some folks like to know motivation behind questions, I'm looking for documentation on the rather basic constraint that ERB tags cannot span multiple lines, which in turn arose from seeing multiple SO questions recently where the OP's were apparently unaware of this constraint.</p>
  
  <p><strong>Update</strong>: Given the Japanese heritage cited in @sawa's answer, allow me to clarify that I'm interested in the most official "English" version of the documentation.</p>