  This paper describes our system, dubbed WS4A (Web Services for All), that
participated in the fourth edition of the BioASQ challenge (2016). We used WS4A
to perform the Question and Answering (QA) task 4b, which consisted on the
retrieval of relevant concepts, documents, snippets, RDF triples, exact answers
and ideal answers for each given question. The novelty in our approach consists
on the maximum exploitation of existing web services in each step of WS4A, such
as the annotation of text, and the retrieval of metadata for each annotation.
The information retrieved included concept identifiers, ontologies, ancestors,
and most importantly, PubMed identifiers. The paper describes the WS4A pipeline
and also presents the precision, recall and f-measure values obtained in task
4b. Our system achieved two second places in two subtasks on one of the five
batches.
