Can we enumerate what we want from the simplified logic service?

   - Existing logic engine can be implemented as an optional module without
   too much trouble.
   - Strongly instead of loosely typed results.
   - Support for parameters.
   - ...

Do we want to support an index date (i.e., avoid assuming today's date)?

Don't we want to forego tokens?  Or are we assuming that consumers of logic
know which rule provider to consult (which may or may not use tokens)?  If
the consumer needs to know which provider to consult and that provider will
presumably be handling the evaluation, then what purpose does the logic
service serve?  Alternatively, rule providers could be registered with the
logic service and then consumers could come to the logic service with a
token (i.e., not need to know the provider).

I'm assuming that we'll defer caching & criteria implementations to the
various forms of logic (at least for now).

What's the purpose of LogicContext now?  In the original design,
LogicContext served a few purposes: (1) proxy for all data requests by
rules, (2) provide a context for evaluations – index date & parameters –
that could be stacked for recursion, (3) context for caching results, and
(4) an abstraction so that the same rule could be run against a patient or
cohort.  If we aren't using logic context for any of these, do we need to
maintain LogicContext at this stage?

Looking forward to the design call.

Cheers,

-Burke

On Wed, Nov 9, 2011 at 10:23 PM, Michael Seaton <[email protected]> wrote:

> **
> Hi all,
>
> I wanted to pick up a thread on the future of Logic that we spent some
> time discussing during the Developers Forum on October 
> 27<https://wiki.openmrs.org/x/5oamAQ>.
>
>
> The overall consensus on the call was that *"Logic is too complicated. We
> wish there were a simpler implementation, that were easier to adapt to
> individual needs.  We wish it were more rigorously tested, including
> performance testing"*.
>
> *Anyone that cares about preserving Logic as it currently exists, or
> wants to see it change in a specific way, please read further*
>
> Specific users of Logic have communicated the following needs:
>
>    - Tammy and her team require more control over the current Logic
>    implementation, and better testing around it, so that future upgrades do
>    not cause serious bugs and performance degradation
>    - Win and Tammy need implementations of Logic that are optimized for
>    running lots of rules for individual patients at a time
>    - Mike needs an implementation of Logic that is optimized for running
>    a single rule for lots of patients at a time as well
>     - Mike wants to be able to choose to not use the existing Logic
>    implementation in favor of an implementation provided by the Reporting
>    module
>
> To accomplish this, the following high-level refactoring steps are being
> considered:
>
>    - Reduce and simplify the number of interfaces and interface methods
>    that Logic exposes in OpenMRS core
>    - De-couple the existing Logic Module in such a way that it is one of
>    many possible "Rule Providers" that can plug into this lighter-weight core
>    framework
>    - Remove, if possible and practical, the need to have a "required"
>    Logic module installed
>
> Specifically, we are considering an approach that would reduce the core
> Logic interfaces to something like:
>
> interface LogicContext;
>
> interface Result; (classes DateResult, NumberResult, ListResult...)
>
>  interface Rule {
>   Set<RuleParameterInfo> getParameterInfo();
>   Class<? extends Result> getReturnType();
>    Result evaluate(Integer patientId, Map<String, Object> parameters,
> LogicContext context);
>  }
>
> interface LogicService {
>   public Result evaluate(Rule rule, Patient patient, Map<String, Object>
> parameters, LogicContext context);
>   public Map<Integer, Result> evaluate(Rule rule, Cohort cohort,
> Map<String, Object> parameters, LogicContext context);
> }
>
>  I would like for this to spur the following potential activities:
>
>    - Give anyone who has not yet been aware of these discussions, or who
>    does not agree with this approach, an opportunity to weigh in and get
>    involved in the process
>    - Make a plan to put this topic onto one or more future Design Forum
>    calls, in order to agree upon the revised design, make tickets, and
>    establish an owner for moving it forward.
>    - Publicize when this Design Forum will occur so that interested
>    parties can be involved as desired
>
> Thanks!
> Mike
>
>
>
>  ------------------------------
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