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The '''Service Modeling Language (SML)''' provides a rich set of constructs for creating models of complex IT services and systems. These models typically include information about configuration, deployment, monitoring, policy, health, capacity planning, target operating range, [[service level agreement]]s, and so on. Models provide value in several important ways.
:'''1.''' Models focus on capturing all invariant aspects of a service/system that must be maintained for the service/system to be functional. They capture as much detail as is necessary, and no more.
:'''2.''' Models are units of communication and collaboration between designers, implementers, operators, and users; and can easily be shared, tracked, and revision controlled. This is important because complex services are often built and maintained by a variety of people playing different roles.
:'''3.''' Models drive [[modularity]], [[Re-use]], and [[standardization]]. Most real-world complex services and systems are composed of sufficiently complex parts. [[Re-use]] and [[standardization]] of services/systems and their parts is a key factor in reducing overall production and operation cost and in increasing reliability.
:'''4.''' Models represent a powerful mechanism for validating changes before applying the changes to a service/system. Also, when changes happen in a running service/system, they can be validated against the intended state described in the model. The actual service/system and its model together enable a self-healing service/system – the ultimate objective. Models of a service/system must necessarily stay decoupled from the live service/system to create the control loop.
:'''5.''' Models enable increased automation of management tasks. Automation facilities exposed by the majority of IT services/systems today could be driven by software – not people – for reliable initial realization of a service/system as well as for ongoing lifecycle management.
A model in SML is realized as a set of interrelated [[XML]] documents. The [[XML]] documents contain information about the parts of an IT service, as well as the constraints that each part must satisfy for the IT service to function properly. Constraints are captured in two ways:
:'''1. Schemas''' – these are constraints on the structure and content of the documents in a model. SML uses a profile of [[XML Schema]] 1.0 as the schema language. SML also defines a set of extensions to [[XML Schema]] to support inter-document references.
:'''2. Rules''' – are [[Boolean expression]]s that constrain the structure and content of documents in a model. SML uses a profile of [[Schematron]] and [[XPath]] 1.0 for rules.
Once a model is defined, one of the important operations on the model is to establish its validity. This involves checking whether all data in a model satisfies the [[XML Schema|schemas]] and rules declared.
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