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The answer can be very simple. For example, I work in drug information. We have a standard section dealing with drug abuse/dependency, which is a vitally important section *when it applies*. However, many drugs are not problematic in this regard and the element is not necessary in those instances. Therefore, it is an optional element for a drug monograph. Honestly, I've yet to see a DTD/Schema that did not contain optional elements, all of them important, but only within their intended context as described above. To answer your revised question within the context of drug information, there are elements (e.g., Indications, Adverse Reactions) that are always mandatory in our monographs, but other elements (a variety of warnings and precautions) that, while common enough and important enough to warrant a "named" element, are not relevant to every single drug monograph and are therefore optional. Another good example would be Black Box Warnings. This is potentially life-or-death information, but is optional because many drugs do not have them. -----Original Message----- From: Costello, Roger L. [mailto:costello@m...] Sent: Sunday, February 26, 2012 10:16 AM To: xml-dev@l... Subject: RE: What does "optional" mean? > I would agree with David Carlisle. > In schema, "optional" doesn't mean ANY of the items you suggest. Yes, I stand corrected. Despite my best efforts, how quickly and easily I fall into the trap of ascribing meaning to constructs in schemas. Let me rephrase my question: Why make one element mandatory and another optional? That is, what is it about some information that it is declared mandatory whereas another information is declared optional? /Roger _______________________________________________________________________ XML-DEV is a publicly archived, unmoderated list hosted by OASIS to support XML implementation and development. To minimize spam in the archives, you must subscribe before posting. [Un]Subscribe/change address: http://www.oasis-open.org/mlmanage/ Or unsubscribe: xml-dev-unsubscribe@l... subscribe: xml-dev-subscribe@l... List archive: http://lists.xml.org/archives/xml-dev/ List Guidelines: http://www.oasis-open.org/maillists/guidelines.php
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