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Subject: RE: [dita] Inheritance of attributes through mapref


I went back to the DITA 1.0 specification to see what that said about map to topic cascading.  What I found is almost identical to the version in the DITA 1.1 spec.:

 

Topic properties in topics and maps

The properties of a topic can be specified in the topic itself or on references to the topic within maps.

. . .

If a property is set in both the map and topic, the map properties are additive if the property (such as the

audience type) takes a list of values. If, instead, the property (such as the importance) takes a single

value, the map property overrides the topic property.

 

Here is the section from the DITA 1.1 spec. for comparison:

 

Topic properties in topics and maps

The properties of a topic (including metadata attributes and metadata elements) can be specified in the

topic itself or in references to the topic within maps.

. . .

If a property is set in both the map and topic, the map properties are additive if the property (such as the

audience type) takes a list of values. If, instead, the property (such as the importance) takes a single

value, the map property overrides the topic property.

 

Given this I think it is hard to argue that the DITA specifications are “wrong”.  I think a case could be made that the specification should be changed. But such a change should really require a full-blown proposal, review, and a vote. And I think that that would need to wait for DITA 1.3. And it might need to wait for DITA 2.0 since it is an incompatible change that would change the behavior for existing documents that conform to the DITA 1.0 and 1.1 specifications as originally written and approved. 

 

My own not too well thought out feeling is that we should try to avoid an incompatible change here altogether by coming up with a syntax that allows authors to explicitly say which behavior they want (override, merge, provide new default values for those cases where no value has been explicitly given, …).  But that will take some care to design and so it too would need to wait for DITA 1.3 or 2.0.

 

    -Jeff

 


From: Su-Laine Yeo [mailto:su-laine.yeo@justsystems.com]
Sent: Wednesday, April 15, 2009 8:35 PM
To: dita
Subject: RE: [dita] Inheritance of attributes through mapref

 

Hi Jeff,

 

Thanks for providing the relevant section of the 1.1 spec. I think the TC should re-examine whether the spec might be wrong. I agree that this thread didn’t start out with the intention of revisiting the 1.1 map-to-topic cascading rules, but if they’re wrong we should fix them before copying the problem over to the map-to-map cascading rules.

 

Having said that, I thought more about the example I gave, and I think the conclusion I first reached is not quite right either. If there is a difference between the conditional values on a topicref and the values on an element in the referenced topic, the processor should have different rules depending on whether the element has values for that attribute or not. In the example, if topic 3 contains an element with no “audience” attribute, that element should be processed as if it inherits audience values from the topicref. However, if topic 3 contains an element with an “audience” attribute, that element should be processed as if its audience values are the intersection between the local values and any audience values on the topicref.

 

When I think about this issue abstractly, it also seems logicially wrong to ask processors to add conditional attribute values that are set at different levels. The way that conditional attributes work is that when you specify what audiences an element is for, you are implicitly saying that it is not for any other audience. E.g. when you say that audience = “c”, you are saying that the audience is not B or A.

 

Here is a second use case, which is an extension of the first but illuminates a few more issues: You are creating a document for three audiences, A, B, and C. The map includes:

 

1) a topic that is common to all audiences

2) a topic in which the entire topic is for audience A only

3) a topic that does not apply to A at all, and contains some elements that apply only to B and some elements that apply only to C

4) a topicref pointing to a submap that includes the following topics:

- 4.1) a topic that applies to B and C only

- 4.2) a topic for B only

- 4.3) a topic that contains some elements that apply only to B and some elements that apply only to C

 

If generating output for audience A, you will want to include topic 1 and 2. Topic 3 and submap 4 should not appear.

If generating output for audience B, you will want the TOC to include topic 1, unconditional and B-only elements from topic 3, topic 4.1, topic 4.2, and unconditional and B-only elements from topic 4.3.

 

There are four ways to indicate that topic 4.1 applies to B and C only:

- mark topicref 4.1 as having audience =”b c”

- mark topic 4.1 as having audience =”b c”

- mark submap 4 as having audience =”b c”

- mark topicref 4 as having audience =”b c”. This is useful because it is possible that the author of submap 4 knew that audiences B and C existed, but was unaware of the existence of audience A, and so did not indicate anywhere within the submap or its topics that 4.1 was a conditional topic. In this case, the author of the parent map should set “audience=”b c” on the topicref that points to submap 4.

 

Using any of these four methods, the processor will give desired results if it follows the following rules for both map-to-topic and map-to-map cascading:

- An element inherits conditional attribute values if it has no local values for that attribute.

- An element is processed as if it has the intersection of local and inherited attribute values, if any local values exist for that attribute.

 

That’s all my brain can handle today :)

 

Best,

Su-Laine

 

 

Su-Laine Yeo
Interaction Design Specialist

JustSystems Canada, Inc.
Office: 778-327-6356
syeo@justsystems.com

www.justsystems.com

 

 

From: Ogden, Jeff [mailto:jogden@ptc.com]
Sent: Wednesday, April 15, 2009 1:55 PM
To: dita
Subject: RE: [dita] Inheritance of attributes through mapref

 

Su-Laine, thanks for providing a concrete use case.

 

Is the use case just a single map and cascading of attribute properties from that map to the topics? It isn’t talking about map to map cascading is it?

 

I thought that the map to topic case was already settled in the DITA 1.1 specification and we were just talking about cascading in the map to map case.  Am I mistaken about that?

 

Here is what the section “Topic properties in topics and maps” in the DITA 1.1 Architecture Spec. says:

 

The properties of a topic (including metadata attributes and metadata elements) can be specified in the

topic itself or in references to the topic within maps.

. . .

If a property is set in both the map and topic, the map properties are additive if the property (such as the

audience type) takes a list of values. If, instead, the property (such as the importance) takes a single

value, the map property overrides the topic property.

 

And I’m arguing that for simplicity’s sake we should follow the same rules for the map to map case as already exist for the map to topic case.

 

   -Jeff

 


From: Su-Laine Yeo [mailto:su-laine.yeo@justsystems.com]
Sent: Tuesday, April 14, 2009 2:45 PM
To: dita
Subject: RE: [dita] Inheritance of attributes through mapref

 

Regarding merging vs. overriding for conditional attributes, let’s consider the following example: You are creating a document for three audiences, A, B, and C. The map includes:

 

1) a topic that is common to all audiences

2) a topic in which the entire topic is for audience A only

3) a topic which does not apply to A at all, and contains some elements that apply only to B and some elements that apply only to C

 

If generating output for audience A, you will want to include topic 1 and 2. Topic 3 should not appear at all, not even in the TOC.

If generating output for audience B, you will want the TOC to include topic 1 and topic 3. Topic 3 should include any unconditional elements, include the elements that apply to B, and exclude the elements that apply only to C.

 

Currently the OT gives the desired behaviour if you set audience=”a” on the topicref to topic 2 and audience=”b c” on the topicref to topic 3. If we were to say that audience attribute values on a topicref are added to the conditional attributes within the target topic, you would not get the desired behaviour in this case, because when generating output for audience B, you would get all the content for audience C in topic 3. I have thought of trying to get the desired behaviour by explicitly conditionalizing all of the elements in topic 3 instead of putting conditions on the topicref, however this is not feasible because you cannot conditionalize element types such as <title>.

 

So I think this particular example supports a rule that conditional attribute values should be processed as the intersection as of the values on the topicref and the values on the further down the hierarchy. I think this is the rule which is actually implemented in the current OT.  

 

Regards,

Su-Laine

 

 

Su-Laine Yeo
Interaction Design Specialist

JustSystems Canada, Inc.
Office: 778-327-6356
syeo@justsystems.com

www.justsystems.com

 

 

> The two open questions are:

> 1) What about attributes like @audience, which take multiple values? If my

> map reference has audience="a b", and the map has audience="c", does "a b"

> override "c", or does this result in "a b c"? If the latter, we will need

> to come up with an authoritative list of which attributes act this way (as

> opposed to the override behavior of @toc and @linking).

 

Don’t we already have a list for the later case (merge)?  If an attribute value cascades and the attribute allows multiple values then. it merges.  If an attribute value cascades and the attribute does not allow multiple values. it overrides.

 

My goal here is just to make the rules for map to map cascading as much like the rules for other cascading as possible because that is more consistent and therefore easier to remember.  And while the DITA 1.1 spec. didn’t talk about map to map cascading explicitly, when it did talk about cascading more generally it talked about merging multi-valued attributes and overriding single values attributes. So it just seem unnec3essairly complicated to introduce a new case.  Note too that this question is about general cascading and that there are separate rules for conref behavior.



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