Subject: [CAS Specification Subgroup] My comments on section 5.1
Folks, Here are my general comments on Section 5.1. Looking forward to your feedback! Best, -ehn 1. Section 5.1.2 requires clarification. The second paragraph invokes Ecore. Then the third paragraph goes on to define features, types, etc - is this just a summary of the contents of Ecore or a specific interpretation of Ecore? The text should be clear on this point. 2. The first candidate compliance point in 5.1.2 has a potential ambiguity. In general well-formedness constraints can be expressed as preconditions, postconditions, and/or invariants. I expect that it's the goal of the framework that all objects in each CAS conform to the type system at all times (invariant). For components, this might be best phrased as both a precondition ("components can assume that the CASes they receive conform to the type system") and as a postcondition ("any object in the CAS which is created by or modified by the component must conform to the type system"). The current wording could be taken to mean that each component must check all the objects in the CAS; I don't think this was the authors' intent. 3. I think it would be clearer to use UML notation consistently. Currently Figure 2 switches to an ad-hoc notation to denote classes and instances, when a UML object diagram would work just as well. 4. The Apache UIMA Notes (end of 5.1.2 on page 22) indicates that the spec is evolving to a simpler design, and that the Apache UIMA implementation is catching up. However, I find the second sentence in the last paragraph a little confusing - is this implementation detail really relevant for the spec? If it's important for each implementation to follow the same pattern, then this needs to become part of the spec itself rather than a side note. The same comment applies to the Apache UIMA note box in 220.127.116.11, page 28. 5. I think that the sofa example in 5.1.3 could be clearer... even though I've written sofa aware code I had to follow the example very carefully to make sure I understood it. It might be better to have an example that uses the sofa in a more application-motivated way (like the multiple text translations example in the SDK document). 6. The degree of flexibility in how to do XML attribute serialization has a direct impact on how hard it is for implementations to comply (18.104.22.168, etc.). My reading of 5.1.4 is that there is more than one legally specified way to represent an XCAS? Shouldn't it be a design goal to have a single, unambiguous way to represent an XCAS? 7. I'm not sure of the proper role of XMI Extensions in the UIMA framework. Section 22.214.171.124 mentions that XMI lets you extend a type system with domain/application specific information. Are we going to indicate the kinds of metadata that an implementation should contemplate here?