Binding Syntax

Binding Syntax

This project is a joint effort between CGIT and Vocabulary.

1. Project now chaired by Rob McClure, building on work from Wendy, Ted, Frank O., Rob H. and Rob S.
2. Current project document with minutes (latest work at the bottom) HERE

Scope

Define the human readable expression of the vocabulary constraints in implementation guides (Model Bindings) and by Realms as published sets of Context Bindings. Define the expression of the Value Set Assertion, a Model Binding, a Context Binding, and a Context Domain constraint. Information expressed in the syntax should be isomorphic to the normative definition of the data items comprising vocabulary constraints in Core Principles and the MIF ballots.

General meeting Agenda

Regular bi-weekly meeting occurs Every Other Tuesday 2p ET for 60 minutes

Next meeting Thursday Q2 Joint Vocab and CGIT, Vocab Hosting in Orlando

1. Agenda:
   1. Review current state
   2. Specific items to discuss at Orlando:
      1. How to support definitively specifying a value set but also allow a sender to send a code not in the expansion set. OPEN allows more flexibility then this use case wants.
   3. Future details for discussion later:
      1. Focus on how to clarify what subsequent types of changes that are Conformant with the specified binding
         1. Expansion changes based on code system version change
         2. Changes in VS definition (a new version) that may or may not lead to a different expansion set
      2. Identify the items in the material below that should be pulled out as not "conformance-focused" and therefore not a part of the formal Binding specification, and instead are Guidance (but should still be stated.)

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Current Working Material

Binding must specify, and only need specify the following

1. The Deterministic Expansion Set. This means every binding MUST fully specify how to determine the value set version and code system version to be used – IE: Which expansion is to be used? The intention is that the specification of the value set expansion will follow the approach noted in the Value Set Definition project. This means that every binding will always be pointing to an actual value set and guidance indicating if all implementers are to use that value set or can do something different.
   1. The exact syntax to be used for the binding statement is to be described here (TBD) and will be fully aligned with the Value Set Definition project and Core Principles
   2. Binding needs to specify how to allow a change in the defined expansion. This may need to be blended into the items noted in section #3. The binding syntax will describe the value set expansion specification and also state if subsequent implementation guides can use a different value set or must only use the specified value set.
      1. Given that a specific value set with specific expansion content must be identified via the parameters:
         1. If "downstream" changes in the value set to be used are allowed, then such a specification must clarify if
            1. A different value set may be used (therefore control and responsibility is ceded to the downstream steward.) This is a SHOULD binding. This is similar to Preferred/example that provide an expansion that may be changed. In V3 this is similar to representative, in CDA it is similar to SHOULD, wherein the binding may be further fully constrained and then used in an implementable guide, but a completely different value set my be bound as an alternative as long as the value set meets the required scope.
            2. Only the value set identified (by the parameters noted) can be used therefore any change in the value set to be used MUST be managed by the original value set steward because they would be creating a new value set definition version. This is a MUST binding.
   3. Alternatively, binding of the coded data element can be deferred to a downstream specification. To do this the coded data element is associated with a semantic category, such as a HL7 V3 concept domain. This association is not a binding. This approach is intended to provide strict guidance on the scope of the value set that will eventually be bound. This association states that value set scope eventually bound MUST be consistent with the scope of the semantic category used to describe the association.
2. Identify behaviours of the data in the instance with respect to the values in the expansion. Through this we describe if a binding may or may not send/receive something not in the expansion determined via the process described above
   1. Restriction to only values that are within the expansion - CLOSED
      1. This approach is expected to be the vast majority. This approach supports the notion described in #1 wherein a subsequent implementation guide can create a new value set that replaces the one noted in the current specification. The guidance provided can also state the behavior subsequent value set authors must follow when creating the value set to be implemented. For example, noting that any subsequent value set created MUST include all codes in the value set in the base specification.
      2. Sender perspective
         1. Must only send values in the expansion
      3. Receiver perspective
         1. Must receive without error values in the expansion
         2. Error for any other value
   2. Binding allows use of values that are not in the expansion - OPEN
      1. Sender perspective:
         1. Must send from expansion if idea is in the expansion
         2. May send something not in expansion if idea is not in the expansion
            1. Must Flag the instance – “OTHR” (Flavour Of Null yet is really not a null)
               1. Send a code and an identification of code system (can be local)
               2. Send text and no code
               3. Send a “reason that expansion code can not be sent” – This is a true flavour of null
      2. Receiver Perspective
         1. Must be able to identify when received code is in the expansion and not report an error
         2. Identify when a data instance contains content not in the expansion but is sent appropriately
3. Describe what further constraints may be applied in a downstream use of the specified binding and yet still be considered conformant with the original binding:
   1. What further constraints on the specified binding can be done, i.e.: what further changes can be made.
   2. Presently an Element Binding may optionally include that the stated binding is a MIN or a MAX binding. When used, both a MIN and MAX binding MUST both be defined. If MIN/MAX is not stated then the binding is to function as a MIN binding.
      1. MIN binding describe the concepts that an implementation MUST fully support
      2. MAX binding MUST include all the MIN concepts with all additional concepts noted as those that SHOULD be supported.
      3. Concepts not included in the MAX binding but from the same code system are EXCLUDED from use. This is consistent with the expectation that even with an OPEN value set as defined below, no concept that falls outside a MAX binding should be sent.
      4. Any constraint on the binding MUST result in a new MAX value set that is a proper subset of the upstreambinding MAX value set.
      5. Any constraint on the binding MUST result in a set of concepts that are within the semantic range of any defined concept domain.
   3. How to implement based on the specified binding without any further constraint, i.e.; How to generate the value set expansion based on the currently specified binding.
   4. Some of this should be defined as default behavior.
   5. V2 Binding strength is in this bucket
   6. Can we clarify that a code may be sent as if the binding was OPEN even when CLOSED (e.g. New lab code for new test when set of allowed known tests are in the existing deterministic expansion

2015-12-08 discussion: MAX value set actually is a computable statement describing concepts that represent the semantic space/concept
domain allowed conceptual domain.
In FHIR a Data Element Definition is exactly the same thing as a V3 "Concept Domain", 
both of which define the semantic space for the model element.
Prose statement that describe "behavior" of subsequent users wherein changes are allowed when that subsequent user wants to 
implement something different than the deterministic binding.
What needs to be done is to pull out items from above that describe this "behavior" stuff and make that not a part of the binding semantic. 
It is aligned and needs to be included, but would not be BINDING SPECIFICATION

2015-12-22 discussion: T. Klein, R. McClure, H. Grain, R. Hausam.
Moved "further allowed constraint" section to #3 from being #2. Cleaned up text in this section and moved content from #1 to this section. 
Section is not complete.
How is DYNAMIC to work? 

1. Allowing changes to expansion set determined by the same value set version based on a different code system version.
2. A restriction of the concepts in the default expansion based on the definition originally specified, using a new value set
3. DYNAMIC in core principles value set binding is restricted to code system version used and need to determine how this should apply to changes in VS version.

Use Cases

This section is where we will list use cases that are to be described using the approach noted

1. Emerging disease tracking registry
2. Data transmission where successive implementation guides can add additional codes to those specified in the specification being constrained
   1. National value set -> state value set -> local value set
3. Start from typical base standard value set with no needed change to implement
   1. Same as above but initial VS was an example and must be made implementable
4. V2 Lab (LRI) examples with the use of national to state to implemented specifications all using binding identifiers.

Old Minutes

2015-07-07_Binding_Minutes
2015-07-21_Binding_Minutes