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« Service Oriented Scheduling - Background Q&A | Thoughts on oBIX 2.0: Defining Enterprise Services »
Thursday
Jul252013

Service Oriented Scheduling (Part 2): EMIX Terms

In a previous post, I described how WS-Calendar introduces schedules to service interactions. It is now straight-forward for two systems to negotiate operating schedules, and to contract for long running processes. If there are many choices for service provider, choosing the best service may take many negotiations. In this post, I describe how using EMIX terms can allow the service requestor rapidly to narrow the choice of service provider.

EMIX, or Energy Market Information Exchange, is a specification developed to meet the information needs of distributed energy markets. Production, distribution, and storage in power markets, in particular, are based upon physical processes and the value at the point of sale is dependent on the time of delivery. EMIX incorporated many semantic elements from WS-Calendar to describe market products over time.

Power generation, in particular, involves large machines, each with particular operating characteristics. Starting a generator may be more expensive than running a generator. Wear and tear may be driven by operating cycles. In EMIX, we took the relied on the characteristics developed for use in wholesale power markets and simplified them. By simplify, I mean we removed the process knowledge. For service interactions, we do not want to know the processes, only the affects.

From a very large number of characteristics that affect how generation can be marketed, we came up with a short list of Market Terms. Using Market Terms, a Service can indicate whether it would be willing to accept an offer.

Operating Terms

Operating terms describe limitations in how the mechanism behind the service operates. It may be unwieldy to provide the service for less than 10 minutes, or the engine may overheat after 4 hours. Operating Terms include:

  • Maximum Run Duration
  • Minimum Run Duration
  • Minimum Recovery Duration
  • Minimum Duration Between Invocations
  • Response Time

Schedule Terms

Schedule terms use vAvailability to describe when the service is available. A single system might offer several services that are identical except for the terms, and terms may vary by schedule. Again let’s go back to the plumber who may have different response times and rates based on time of day.

Summary of SO Scheduling

These are not only the terms of generation market, they are the terms for negotiations between any two systems, or even for the plumber I described in part 1. For example, a plumber could publish a schedule (availability) with a labor rate for business hours, another schedule with rate for early evening and Saturday service, and still a third for overnight service. Availability can be stacked; that plumber can lay a short-term unavailability atop the other schedules, interrupting the standing availabilities with a vacation.

Together, WS-Calendar and EMIX Terms provide the semantics needed to advertise, negotiate, and transact for long running services and physical interactions.

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