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Subject: RE: [dita] Attribute cascade proposal
Arbortext has an a proprietary approach to this, too, but it's done in the definition of the attribute specialization, and not specified in the map, so it may not work for all the necessary use cases. If an attribute is a specialization of props-nooverride - that is, its @domains token looks like "a(props props-nooverride attrName)", then for that attribute - that attribute only, and all instances of that attribute - new values on child branches/elements override values inherited from parent branches/elements, instead of merging. (Yes, the naming is awkward and probably backwards.) This wouldn't handle the specific example here, because @platform wouldn't be specialized from props-nooverride, and you can't make some instances of 'nooverrides' attributes merged and others non-merging, but it seems to have worked well enough for our purposes. Chris -----Original Message----- From: Robert D Anderson [mailto:robander@us.ibm.com] Sent: Tuesday, May 21, 2013 3:17 PM To: dita Subject: [dita] Attribute cascade proposal Hi, As with the branch filtering item, I'm hoping to get some initial TC feedback on expected direction with the cascade item. Basic use case is a map like the following, applies to 3 platforms: <map platform="mac win linux"> .... <topicref href="nested-branch.dita" platform="mac">...</topicref> .... </map> Per the spec today, when platform cascades, values combine. This means if I (accurately) indicate that my map applies to 3 platforms, I cannot then restrict one section of that map to a specific platform - values combine, so that even my mac-only branch is treated as mac/win/linux. I expect there are many cases where this is valid and proper - and applications have implemented this - so we cannot simply change the behavior. The other option is to provide author or tool control over the behavior. Potential solutions considered: 1) Extend @lockmeta to add some control over whether attributes get merged. I don't like this because it's on <topicmeta> -- so to find out if @platform cascades, we might have to check parent/topicmeta/@lockmeta, then parent/parent/topicmeta/@lockmeta, and so on -- too indirect and likely to be confusing. 2) Add a token to attributes. For the nested case above, I could say something like platform="#override# mac" or similar - indicate this does not merge with ancestor values. Feels clunky and likely to be painful to use, possibly to implement. 3) Change the spec to make this optional - tools can implement cascade with or without merging, possibly through some tool option. Have not really considered this fully, and could mean you get very different behavior in different apps. 4) Add a new attribute in maps, something like cascade="merge | nomerge". Would likely leave this open to other values, with 2 (or more) predefined tokens - similar to how chunking works - allowing tools to expand their support to new types of merging. Default could be the predefined token "merge", to keep current behavior. Not sure if this attribute would itself cascade / override lower values, not fully thought out yet. At the moment I'm leaning towards the last option in that list. The first two seem too complex / difficult to use. The third I'd be willing to consider but for now at least I think the goal is to have this a standardized behavior, which pushes us to #4. Thoughts? Robert D Anderson IBM Authoring Tools Development Chief Architect, DITA Open Toolkit (http://dita-ot.sourceforge.net/) --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. Follow this link to all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php
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