Communication Process Model
Closed: May 2009 because it is being super ceded by new work on a dynamic model.
NOTE: The concepts on this page have not been formally approved yet. Motion: (May2006) MnM supports replacing the existing methodology of receiver responsibilities and application roles with the activity-diagram-based approach described below, and will seek endorsement of the committees at the Facilitators’ Roundtable meeting Thursday. If endorsed, this will be documented in a whitepaper to be incorporated in the HDF (and V3 Guide, etc.) and referred to Tooling and Publishing committees for implementation. (Austin, Patrick – 9:0:1) motion passes.
A CPM expresses our understanding of flows or patterns of behavior around the exchange of groups of Composite Message Types. They describe under what circumstances a composite message type is transmitted.
Note: 2008/05/04 - Discussion deferred as the ARB is working on this as an action item. They'll come back to MnM when they have something to discuss.
A CPM is documented using an Activity Diagrams (basically flowdiagrams with decision points), with "swimlanes" that represent application roles. They are much more expressive than sequence (interaction) diagrams. The modelling is limited to communication related activities, the aim is not to "model the whole world". Decision Points show choices, but don't specify how the choice should be made, as that is application/business rule behavior which is out of scope of HL7.
At this level of abstraction the delivery method of the interactions is of no relevance whatsoever.
CPMs may exist at various levels, e.g.
- higher level abstract CPMs (a.k.a. stereotype, non implementable) - e.g. a generic Order workflow
- Domains may define 1, or a set of, CPMs. CPMs may follow archetypes/stereotypes (e.g. orders). Nuance differences, constrain/extend CPM in domain.
- CPMs can be profiled for conformance reasons. CPMs can be constrained by committees as well. Constraining a CPM may be done in the form of reducing the number of options by the removal of decision points from a CPM, constraining the circumstances where a trigger event is invoked.
- Extended CPMs. It has yet to be established how “extensions” are allowed (e.g. for realms). We may have to uspport “local extensions in a separate namespace” on dynamic models expressed by CPMs.
CPMs may have multipe entry points. CPMs form the basis for Conformance Statements (e.g. "I am a Lab system and I support the following CPMs").
A Communication Process Instance (CPI) identifies one partular instance of a CPM. Activity Diagrams that show 1 specific CPI (which contains no more "open" decision points) is effectively a Sequence Diagram. Activity Diagrams are normative (and contain information we don't currently capture), Sequence Diagram are examplary. Sequence Diagrams will be used in combination with storyboards, because storyboards typically describe a CPI.
A CPM has an artefact ID (e.g. POLB_PM123456UV01), a CPI is identified by means of an II attribute. The CPI identifier is known in other environments as the business process identifier or conversation ID. Examples of a similar concept (limited to query/response based CPMs) already present in v3 interactions is "queryId". Both identifiers are referenced in the contractual portion of the transmision wrapper.
CPMs have been introduced to cover the following requirements:
- they need to define what Composite Message Type can be exchanged
- they need to indicate types of systems (Application Roles) are capable of sending which composite message types
- they identify under what circumstances a composite message type is transmitted
- they need to be able to express our understanding of flows or patterns of behavior around the exchange of groups of composite messages
- set expectations for conformance (including from a dynamic perspective). Conformance Statement: "I am a Lab system and I support the following patterns".
- lower the number of interaction artefacts necessary to cover the various scenarios in a domain. For example avoids having to define all interactions twice in the Lab domain (with and without Receiver Responsibilities).
- how to call artefact. HDF "dynamic view". Activity Diagram used to document CPM: Communication process Model, Communication Process Instance. This is part of the dynamic model.
- transition: transform current receiver responsibilities into simple CPMs. Committees can define more complex ones.
- Remove "receiver responsibility" from HL7 Interaction concept. Interaction = tuple (Trigger Event, Composite Message Type).
Transitioning from the old dynamic model (expressed in terms of Receiver Responsibilities, with an Interaction ID being a tuple of (Trigger Event, Composite Message Type, Receiver Responsibilities) to a CPM based dynamic model calls for several changes to be made. The new CPM based ynamic model should be in place during the January 2007 WGM.
- Transform to take existing dynamic model content (e.g. receiver responsibilities) in to CPMs. Create identifiers for these “old” CPMs, e.g. by using the existing interaction id for the ‘request’, with new “artifact” portion.
- Need to have some starting-point patterns for committees
- Remove Receiver Responsibilities from the concept of Interaction ID.
The introduction of CPMs has a number of consequences for the MCCI materials.
- Interaction ID turns into a tuple consisting of Trigger Event and Composite Message Type (see Interaction (new dynamic model) for details). If an Application Response was generated based on an Interaction Based trigger event (e.g. a qyery response interaction) then such one interaction requires Acknowledgement/AcknowledgementDetail classes in its wrapper. If an Application Response was generated based on an State Based trigger event (e.g. a Promise interaction) then .. this leads to the question what the role of the Acknowledgement/AcknowledgementDetail classes are in this new dynamic model.
- It could mean we’ll have only 1 Transmission Wrapper model which is used by all interactions, irrespective of whether they’re used in initial interactions or in responses.
- An attribute will have to be added to interaction instances to specify to what CPM they conform to.
- The identification of the CPI (effectively a conversation ID) needs to be added to the transmission(?) wrapper.
A Laboratory Order, followed by a Promise, an optional modification of the Order by the Laboratory, and a final labresult constitutes a CPM.
- The use of some Interactions (e.g. Accept Level Acknowledgement,
- Most Storyboard Diagrams in the HL7 v3 standard describe a CPI or (part of) a CPM.
- Implementers will declare:
- I support application role X, with CPMs A & D, and application role Y with CPMs A & B
- They may choose to restrict a pattern by indicating that certain ‘decision points’ will have a more limited number of outcomes. This would be considered “interoperable, but not strictly conformant.”
- If there is need for a different CPM (because they want to market a different set of constraints a ‘conformant’), they need to convince the committee that it is a useful CPM.
- Committees will:
- Define each CPM as a distinct artifact
- Attempt to re-use application role labels across CPMs where general business responsibility is consistent
- Other rules:
- Once a CPM has been invoked, the CPM cannot be changed throughout the duration of the conversation.
Note from the INM out of cycle meeting: Even if a Transmission SLA is in place, we may still have run-time SLA options which have to be conveyed within an interaction instance that may have an influence on how & when an interaction is responded to.
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