Poster session includes a "poster" + "article"? When we are accepted in a poster session, does it mean that we need to provide a "poster" (usually in A0 size) + an "article" which explains the topic in a separate file ? Or both poster and article are included in a single PDF file ? 

And also this article must include an "abstract" like usual papers?  

I ask this question because I have received a strange email from a workshop as follows :


  Posters have to  be formatted in LNCS-style and not exceed 1 page in
  length, with a PDF  draft of the proposed poster included as page 2 of
  the submission (A0 size  in portrait mode,  W 841mm x H 1189 mm, with
  all fonts embedded in the  PDF file). In addition, poster titles
  should always start with the  phrase "Poster Abstract:"


Here is the website of the conference : http://deic.uab.cat/conferences/cbt/cbt2018/

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It'd the best to ask conference organizers for the clarification. Organizers of conferences are usually very friendly and quite responsive, so there's no harm in asking. And they will be able to give the precise and authoritative answers to your question.