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Subject: [emergency] Re: Attributes vs Elements
Oh Boy! Lemme find a match. Sorry, couldn't help myself there for a second. I'm better now. Whew! I usually duck this one, and just use elements as much as I can. However, I plan to stay out of this debate, so don't take that as a recommendation. Ciao, Rex At 2:09 PM -0400 5/8/03, R. Allen Wyke wrote: >Oh boy - you have just stepped into one of the biggest debates of all >times. However, you are right - it is appropriate for us to discuss this >and to do so within the larger audience of the EM TC. I will take what >you have, and run with it (fully realizing that I am sure it will >stimulate some responses :) > >The objective of this discussion will be to formalize some *basic* >guidelines we should all adhere to for any XML schemas we develop. I >think it is best we do not set hard and fast rules and that we provide >some wiggle room for each SC, but we do need to be consistent in at >least some fashion. I will include the outcome in the guidelines >document I am working on. > >For the context of this debate and to start the discussion, let me list >the basis of how I came to a recommendation: > >1. There is no single and always correct answer. > >2. You will be hard pressed to find a definitive human definition of >"element" or "attribute", in the context of XML, to provide a single >answer to this question. However, it is generally accepted that >attributes are metadata about its containing element with some implied >inheritance in any subsequent child elements. > >3. The 6th design goal of the original XML Recommendation >http://www.w3.org/TR/REC-xml#sec-origin-goals) states that "XML >documents should be human-legible and reasonably clear." > >4. There is a technical argument within XML Schema Part 2: Datatypes >(around internationalization), to keep human-readable text out of >attribute values. Under the xsd:string datatype >(http://www.w3.org/TR/xmlschema-2#string), it says: > >NOTE: Many human languages have writing systems that require child >elements for control of aspects such as bidirectional formating or ruby >annotation (see [Ruby] and Section 8.2.4 Overriding the bidirectional >algorithm: the BDO element of [HTML 4.01]). Thus, string, as a simple >type that can contain only characters but not child elements, is often >not suitable for representing text. In such situations, a complex type >that allows mixed content should be considered. For more information, >see Section 5.5 Any Element, Any Attribute of [XML Schema Language: Part >2 Primer]. > >In not so many words, it says ’Äúdon't use attributes for human-readable >text’Äù. You are not able to include elements, for further description, in >attribute values and things like hard returns are problematic from a >programming standpoint (not too mention a long attribute value violates >#3 above). > >5. From a programming standpoint, accessing elements vs. attributes >isn't very different if you use a good parser/processor. > >Based on these, I recommend we do the following as part of our >guidelines. > >-------------------------- >Any and all schema developed by the EM TC and its SCs SHOULD: > >1. in general practice separate metadata into attributes. > >2. make every effort to keep documents human-legible and reasonably >clear as specified in the Origin and Goals >(http://www.w3.org/TR/REC-xml#sec-origin-goals) of the "Extensible >Markup Language (XML) 1.0 (Second Edition)". >-------------------------- > >Ok, the gasoline has been poured. I am sure someone will now strike the >match :) > >Allen > >On Wed, 2003-05-07 at 18:32, Weltman, Jerry wrote: >> Allen and Rick, >> >> During the Notifications and Messaging SC a couple of weeks ago, I >> brought up the issue that we could be using attributes for some of the >> data instead of elements. The response was overwhelming that we should >> not be using attributes, which is fine by me. But I am wondering >> whether there should be some debate among the TC in general on this > > issue since it seems like we would prefer that all of the TC's XML >> structures have a similar style. >> >> Or perhaps I am missing something. Is there something about the work >> we are doing that makes attribute-free XML structures an obvious >> common goal? > >> Jerry >-- >R. Allen Wyke >Chair, Emergency Management TC >emtc@nc.rr.com >http://www.oasis-open.org/committees/emergency -- Rex Brooks GeoAddress: 1361-A Addison, Berkeley, CA, 94702 USA, Earth W3Address: http://www.starbourne.com Email: rexb@starbourne.com Tel: 510-849-2309 Fax: By Request
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