Contents

• Summary
• Service Modeling Language Specifications
• From the W3C Staff Comment
• From the Announcement
• SML Background and Commentary
• W3C SML Working Group
• Principal References

Update 2007-04-27: On April 27, 2007 W3C announced the launch of a new Service Modeling Language (SML) Working Group, chartered through through 31-October-2008 to produce W3C Recommendations for SML, adding extensions to the W3C XML Schema language for inter-document references and user-defined constraints.

[March 26, 2007] W3C has acknowledged receipt of a Member Submission for the Service Modeling Language (SML) specification, which may be used to model complex IT services and systems, including their structure, constraints, policies, and best practices. The submission request was made by BEA, CA, Cisco, EMC (Documentum), HP, IBM, Intel, Microsoft, and Sun Microsystems with the recommendation that W3C form a Working Group whose mission would be "to produce W3C Recommendations for Services Modeling Language by refining the Submission, addressing implementation experience, and interoperability feedback from the Submission."

The SML submission includes the primary Service Modeling Language, Version 1.0 specification, together with a companion SML Interchange Format Version 1.0. As defined in the Service Modeling Language Specification, an SML model is a collection of XML documents that may be used to describe such things as a set of IT resources, services, and their interrelations. The SML Interchange Format (SML-IF) document defines an implementation-neutral interchange format that preserves the content and interrelationships among the documents that make up an SML model, or a portion of an SML model.

SML models typically include information about configuration, deployment, monitoring, policy, health, capacity planning, target operating range, service level agreements, and so on. An SML model, realized as a set of interrelated XML documents, contains 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.

SML constraints are captured in two ways: (1) Schemas, which express 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, and defines a set of extensions to XML Schema to support inter-document references. (2) Rules, which are Boolean expressions 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 schemas and rules declared.

SML is designed to support the creation of best practices and policies that automate the services' validation, development, operations, updates and end-of-life — the full lifecycle. SML does not prescribe a specific IT model or set of models; instead, it defines the syntax and semantics that all SML models must follow: their base vocabulary, the rules of composition, the grammar, and the syntax. SML specifies: (1) Profiles for the use of XML 1.0 Schema and Schematron to define service models; (2) Extensions to support and constrain inter-document references in those models; (3) Inter-document uniqueness and key definitions plus the ability to use them across documents; (4) Rules to capture best practices and policies.

The W3C Staff comment on the submission notes that W3C normally "refrains from standardizing XML vocabularies for specific application areas, unless they have foundational character (e.g., XML Schema, XSLT) or have very wide application (HTML, MathML). However, SML is not a conventional XML vocabulary, as it defines no elements or attributes with any semantics specifically related to IT services or systems. Instead, as a profile and an extension of XML Schema 1.0 and Schematron, an SML model (description of a system) consists of: (1) a set of definition documents using the XML Schema 1.0 vocabulary, optionally using specific types, extension elements, extension attributes defined in the SML specification, Schematron rules/documents; (2) a set of instance documents which conform to the definition documents.

Thus, the Staff comment notes, SML provides at the same time a layered extension of XML Schema, which allows validation to enforce structural and referential integrity constraints within a single XML document but also across multiple documents, and a subset or profile of XML Schema 1.0. The most important extensions support inter-document validity constraints: the 'sml:reference' type, used for inter-document references; the 'smlfn:deref()' extension function for XPath 1.0, which finds reference elements and retrieves the nodes they refer to; and multi-document analogues to the intra-document identity constraints of XML Schema 1.0.

SML is said to relate very closely to the work of the W3C XML Schema Working Group, in the XML Activity, and slightly less closely to that of various groups in the Semantic Web Activity, in particular those responsible for RDF Schema — first the RDF Schema Working Group, later the RDF Core Working Group.

Two possibilities are mentioned in the W3C Staff comment for progressing the SML within W3C, where the second option seems preferable: (1) recharter the existing XML Schema WG to start from this submission, or (2) form a separate Working Group to work on SML as a layered approach to multi-document validation, compatible with and relying upon XML Schema as the lower layer, using the SML submission as the starting point for a requirements document.

Service Modeling Language Specifications

SML Version 1.0 was published in February 2007 as a collection of several files, including the SML Specification (PDF, XHTML), SML XSD schema, SML XSD schema for errors, SML Interchange Format (PDF, XHTML), and SML Interchange XSD schema.

• Service Modeling Language, Version 1.0. W3C Member Submission. 21-March-2007. Latest version URI: http://www.w3.org/Submission/sml/. Authors: John Arwe (IBM), Jordan Boucher (Sun), Pratul Dublish (Microsoft), Zulah Eckert (BEA), Dave Ehnebuske (IBM), Jon Hass (Dell), Steve Jerman (Cisco), Heather Kreger (IBM), Vincent Kowalski (BMC), Milan Milenkovic (Intel), Bryan Murray (HP), Phil Prasek (HP), Junaid Saiyed (EMC), Harm Sluiman (IBM), Bassam Tabbara (Microsoft), Vijay Tewari (Intel), William Vambenepe (HP), Marv Waschke (CA), Andrea Westerinen (Microsoft).

  [...] SML Models provide value in several important ways:

  • Models focus on capturing all invariant aspects of a service/system that must be maintained for the service/system to be functional.
  • 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.
  • 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.
  • 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.
  • 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.

• SML Interchange Format Version 1.0. W3C Member Submission. 21-March-2007. Latest version URI: http://www.w3.org/Submission/sml-if/. Authors John Arwe (IBM), Jordan Boucher (Sun), Pratul Dublish (Microsoft), Zulah Eckert (BEA), Dave Ehnebuske (IBM), Jon Hass (Dell), Steve Jerman (Cisco), Heather Kreger (IBM), Vincent Kowalski (BMC), Milan Milenkovic (Intel), Bryan Murray (HP), Phil Prasek (HP), Junaid Saiyed (EMC), Harm Sluiman (IBM), Bassam Tabbara (Microsoft), Vijay Tewari (Intel), William Vambenepe (HP), Marv Waschke (CA), Andrea Westerinen (Microsoft).

  Introduction: As defined in the Service Modeling Language (SML) Specification [1] an SML model is a collection of XML documents that may be used to describe such things as a set of IT resources, services and their interrelations.

  In every SML model there is a distinguished subset of the documents that comprise it, called the model definition documents. A model's definition documents describe the abstract structure of the model, and provide much of the information a model validator needs to decide whether the model as a whole is valid. The other documents in the model, called its model instance documents, describe or support the description of the individual resources the model portrays. Broadly speaking, an SML model is a graph of nodes connected to one another by arcs. The nodes are formed by model instance documents; explicit inter-document references form its arcs.

  The SML Specification identifies two categories of model definition documents that participate in model validation: Schema documents and rule documents. Schema documents in a model are XML documents that conform to the SML-defined subset and extensions to XML Schema 1.0. Rule documents in a model are XML documents that conform to the SML-defined subset and extensions of Schematron [4].

  To ensure accurate and convenient interchange of the documents that make up an SML model or a portion of an SML model, it is useful to define an implementation-neutral interchange format that preserves the content and interrelationships among the documents. This specification defines a standard format called the SML Interchange Format (SML-IF) that does that. The specification consists of two parts: The first part is an informal description of SML-IF to set the context. This is followed in part two by SML-IF's normative definition.

From the W3C Staff Comment

Excerpt from the Team Comment on Service Modeling Language (SML) Submission, by C. M. Sperberg-McQueen and Philippe Le Hégaret:

Relationship to the XML Schema Working Group: Viewed as a schema language, SML embodies a critique of XML Schema 1.0 from a particular angle. The profile of XML Schema effectively provides a list of schema constructs which have proven problematic for users and software developers at least in the context of SML. The extensions to XML Schema 1.0 may be interpreted as a request for enhancement, together with a design showing a possible realization of the enhancement.

But SML is properly viewed not as a schema language competing with XML Schema 1.0, nor as a revision of XML Schema 1.0, but as a layer of inter-document constraints designed to be used on top of XML Schema.

The key contribution of SML to validation lies in its handling of inter-document constraints, which can and should be layered on top of the single-document validation of XML Schema or other schema languages. Any work on SML as a language for cross-document validation should be performed in regular and extensive consultation with the XML Schema Working Group, but should almost certainly be described in a separate specification, probably prepared by a different Working Group. It should be noted that the addition of assertions to XML Schema 1.1 may make at least some uses of Schematron unnecessary for SML. That area presents a possible incompatibility between SML and existing W3C work.

Relationship to the Semantic Web Activity, RDF Schema: Many groups in the Semantic Web Activity have an interest in data integration from multiple sources. The validation of inter-document references, however, is not of primary importance or interest in the Semantic Web context. More interest attaches to the imposition of constraints on the RDF graph of the information in the documents being validated, but this has no necessary relation to the original representation of the information in one or several XML documents, or to inter-document references.

Semantic Web technologies rely on the URI as the atomic unit of naming and identity; they will tend to be less useful for manipulating information about SML models which use end-point references (EPRs) instead of or in addition to URIs. For that reason, it is not clear that any groups in the Semantic Web Activity will take an active interest in SML, but any further work on SML should certainly solicit input from the Semantic Web Activity.

Relationship to Web Services: Section 3.3 of SML provides two mechanisms for reference schemes, namely Uniform Resource Identifiers (URIs) and endpoint references (EPRs). It should be noted that the Web Services Addressing specification does not define equivalence between two EPRs, and specifies that "using abstract properties of an EPR other than [destination] to identify resources is contrary to the Web Services Addressing recommendation". The example in section 3.3.2 (EPR Scheme) therefore seems misleading in its use of EPR reference parameters. We believe that using reference parameters in an EPR that is included in an SML 1.0 document should be avoided.

From the Announcement

Excerpt from: "Technology Leaders Submit Modeling Specification to the World Wide Web Consortium. Industry Takes Next Step In Standardizing the Description of System Information in XML Formats." See also the Quote Sheet.

BEA Systems Inc., BMC Software Inc., CA, Cisco Systems Inc., Dell Inc., EMC Corp., HP, IBM Corp., Intel Corporation, Microsoft Corp. and Sun Microsystems Inc. today announced they have submitted a specification to the World Wide Web Consortium (W3C) for review as an industrywide standard. Called the Service Modeling Language (SML), the specification defines a consistent way to communicate how computer networks, applications, servers and other IT resources are described — or modeled — in extensible markup language (XML) and can help businesses more seamlessly manage the services that are built on these resources. In addition to the base SML specification, a companion specification was submitted to the W3C. Called the SML Interchange Format (SML-IF), it defines how to exchange SML models between applications.

With industry collaboration, SML enables a hierarchy of IT resource models to be created from reusable building blocks rather than requiring custom descriptions of every service, reducing costs and system complexity for customers. These blocks can be defined at the appropriate level of granularity for desired-state management. They include validation constraints that increase the reliability of integrations, opening the door to increased automation. If adopted as a standard, SML will address the industry problem of numerous methods representing the same IT resource. Currently, the use of different formats requires a translation process that can lead to the loss or misinterpretation of technical details.

SML offers support for rich constraints and alignment with XML message exchange architectures — unique properties that make it well-suited for modeling IT resources and services. SML allows developers to build modeling information for applications, IT infrastructure and services that can be used during all stages of the resource life cycle, including deployment and configuration management and resource updating. They are also useful for tactical processes such as management of service levels, availability and capacity.

SML Background and Commentary

• [March 22, 2007] "Modeling's The Next Big Project on W3C Runway." By Clint Boulton. From InternetNews.com (March 22, 2007). "IBM, HP, Microsoft, and several other top technology vendors are hoping the World Wide Web Consortium (W3C) will develop a new standard specification for describing computer services in XML. The vendors said the W3C has acknowledged the Service Modeling Language (SML), which uses XML to describe how computer networks, applications, servers, storage and other IT resources be modeled, as a candidate for a new standard. If the spec becomes a standard, it would help eradicate a major stumbling block to creating XML-based services that can be used in environments where products from multiple vendors are employed. SML, which embodies the spirit of service-oriented architecture (SOA) (define) distributed computing, will help corporations craft service models at a time when systems topologies are becoming increasingly convoluted. IBM's Telford said users can use SML to compare the current state of a server to the desired state of a server. Users can bridge the gap by making changes in the IT environment, a benefit that can also ensure compliance at a time when regulations call for more control of data in a computer system. William Vambenepe, a distinguished technologist for HP Software, said SML ensures high levels of regularity within a system..."

• [March 22, 2007] "New Standard Seeks To Allow Services To Talk To Each Other." By Charles Babcock. From InformationWeek (March 22, 2007). "IBM, Microsoft, HP, Sun Microsystems, Dell, Intel, Cisco, CA, EMC, BEA Systems, and BMC rally around Service Modeling Language. A new standard that will allow services that have never shaken hands before to interoperate was submitted Thursday to the World Wide Web Consortium. Many of the contributors to the specification are likely to start incorporating SML into their systems and network management products before it's ratified as a standard, said Ed Anderson, director of the Dynamic Systems Initiative at Microsoft. 'This is a critical step for us. SML will simplify the management of services generally,' Anderson said in an interview. It's the first time such a broad industry coalition has gotten behind the same standard, he added. SML will supply a consistent way to describe networks, applications, servers and other computer resources in XML, the Extensible Markup Language already widely used for documents on the Web, said Wayne Adams, senior technologist with EMC, the storage and storage management vendor. With XML-parsing already built into many networked systems, SML will fit into many existing infrastructures. An ability to describe system resources in XML will allow services to be built that will work with other SML-modeled services. SML will also help generate a hierarchy of IT resources from reuseable, SML-defined building blocks rather than requiring custom descriptions each time IT seeks to build a service. IBM with its Tivoli systems management, HP with OpenView, CA with CA-Unicenter, and BMC with Patrol are among the top data center systems management vendors, along with Microsoft's System Center Configuration Manager for its Windows platform..."

• [March 22, 2007] CAM Approach and Submission of SML to W3C. By David Webber. Post to OASIS CAM TC List. "On brief initial review of this, it seems like the team has followed very much the CAM approach here... SML creates a lot of extension syntax whereas CAM uses XPath directly; CAM assertions are business-user friendly syntax, whereas SML uses arcane logic syntax; a CAM processor could easily incorporate an SML step as part of post-processing; CAM can handle multiple structures and structure variances better, I believe, and also context driven parsing... good to have W3C validating [something like the CAM approach]..."

• [March 14, 2007] "Updated Version of the Service Modeling Language (SML) Specification." By John Arwe, Jordan Boucher, et al., Blogged in XML Daily News. Draft Specification. Industry partners have published a revised version of the Service Modeling Language (SML) specification, its companion "SML Interchange Format" document, and related resources. The SML Version 1.0 Draft Specification of 28-February-2007 was produced by corporate authors BEA, BMC, CA, Cisco, Dell, EMC, HP, IBM, Intel, Microsoft, and Sun. The Service Modeling Language (SML) is used to model complex IT services and systems, including their structure, constraints, policies, and best practices. SML is based on a profile on XML Schema and Schematron. Models as defined in SML typically include information about configuration, deployment, monitoring, policy, health, capacity planning, target operating range, service level agreements, 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. (2) Models are units of communication and collaboration between designers, implementers, operators, and users; and can easily be shared, tracked, and revision controlled. (3) Models drive modularity, re-use, and standardization, 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; 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. 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: [A] 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. [B]. Rules: are Boolean expressions that constrain the structure and content of documents in a model. SML uses a profile of Schematron and XPath 1.0 for rules. To ensure accurate and convenient interchange of the XML documents that make up an SML model or a portion of an SML model, it is useful to define an implementation- neutral interchange format that preserves the content and interrelationships among the documents. The "SML Interchange Format" specification defines such a standard format called the SML Interchange Format (SML-IF).

• [February 05, 2007] "Service Modeling Language Manages IT Assets." By Andrew Conry-Murray. From Network Computing (February 05, 2007). "A high-powered working group is striving to improve IT management and data-center automation with a common language to describe heterogeneous IT assets. The Service Modeling Language (SML) is an XML-based schema to define, or model, information about hardware, software, applications and services. This common language will make it easier to share information among disparate IT tools and provide a foundation for automating common tasks, such as application provisioning, configuration management and asset monitoring. SML also is being positioned as a way to overcome the barriers to federation and reconciliation of disparate data in CMDBs (configuration management databases). The outlook for the standard is a good one, judging by the big vendors that have backed it and the progress made thus far: The most recent draft of the specification was released in November 2006, and the specification may be submitted to a standards body this quarter. The basic goal of the SML working group is to create a grammar that describes everything in an IT environment — hardware, software, applications and, eventually, services — in a unified way. With a common vocabulary in place, third-party tools can more easily share information about the assets they manage. The Distributed Management Task Force's CIM (Common Information Model) offers much of what SML aims to do and is in wide use. SML proponents say they are evolving CIM by writing definitions in native XML, making SML built for Web services from the ground up. Today, there's a host of software for building, parsing and validating XML schemas, which will make it easier for vendors to create tools that can understand SML. By contrast, a DMTF specification exists for representing CIM in XML, but it requires complex transformations. That said, the SML working group says it will use CIM definitions wherever possible and will work closely with the DMTF to avoid reinventing the wheel. Although the major backers of WS-Management and WSDM will continue to support each technology, IBM and Microsoft are also converging the two specifications into a single spec tentatively called WS-Unified Management..."

• [January 15, 2007] " Update on the Service Modeling Language (SML)." By Sam Ramji (Microsoft Open Source Labs). Port 25. The author reports on an update to the Service Modeling Language draft specification created by Microsoft and a number of other leading technology companies. SML is designed to model complex IT services and systems, including their structure, constraints, policies, and best practices. SML is based on a profile on XML Schema and Schematron. SML was created by the SML working group whose members are BEA, BMC, Cisco, Dell, EMC, HP, IBM, Intel, Microsoft and Sun. SML will allow for the creation of best practices and policies that automate the services' validation, development, operations, updates and end-of-life — the full lifecycle. SML does not prescribe a specific IT model or set of models; instead, it defines the syntax and semantics that all SML models must follow: their base vocabulary, the rules of composition, the grammar and the syntax. SML Specifies: (1) Profiles for the use of XML 1.0 Schema and Schematron to define service models; (2) Extensions to support and constrain inter-document references in those models; (3) Inter-document uniqueness and key definitions plus the ability to use them across documents; (4) Rules to capture best practices and policies. Ramji says: "On September 12th the public feedback workshop was held and a good deal of feedback was provided both by community members in attendance and by those submitting feedback via email. One of the key topics was the name of this language as many felt the SML title didn't full capture the intent or capabilities of the specification. Pratul Dublish, Senior Program Manager at Microsoft, has a blog entry regarding this discussion. The Working Group has announced an Interoperability Workshop for interoperability testing between different implementations of the specifications. The workshop is open to companies and individuals willing to bring an implementation of the latest published specifications to the workshop...

• [August 17, 2006] "Service Modeling Language: Industry Collaboration for Improved Systems Management." Sam Ramji and MichaelF. On July 31, 2006 Microsoft and a number of other leading technology companies including: BEA, Cisco, Sun, IBM, Intel, HP, BMC, and Dell announced 'they have published a draft of a new specification that defines a consistent way to express how computer networks, applications, servers and other IT resources are described or modeled in Extensible Markup Language (XML) so businesses can more easily manage the services that are built on these resources...' This sounds great, but we wanted some more details regarding the scope of this draft specification, its impact on the industry and the technical details behind it. To get those answers Sam interviewed Praerit Gart, Senior Director of the Dynamic Systems Foundation Team, to discuss the announcement and what it means to the industry and IT Professionals. You can also download the specification and schema. The team will be taking direct feedback on the schema, as well as holding a public Feedback Review Meeting on September 12, 2006... See also the Podcast.

• [August 15, 2006] "Meet the Specs: SML Models Complex IT Systems." By Kane Scarlett. From IBM developerWorks. "The Service Modeling Language specification is a proposed open standard that defines a modeling language complete with a set of constructs to help you model complex system hierarchies for components that manage such elements as configuration, monitoring, policy, health, capacity planning, and Service Level Agreements (SLA). One of the effects of SML is to increase the automation of management tasks, thereby reducing the need for a human to intervene in necessary adjustments. In today's multivendor environment, customers demand open, standards-based methods to accelerate integration of management software technologies, methods that include the ability to speed software deployments and to reduce the overhead caused by needing human intervention. You can use SML to capture knowledge about the different parts of complex IT systems and the constraints that these parts must satisfy in order for the IT system to function properly. Using SML generates several effects, one that addresses the needs of the autonomic computing adopter and one that is shared by everyone employing the language: (1) To increase automation of some management tasks (because the knowledge is captured in a machine-readable way); (2) To allow those with different expertise, who touch the system at different points in the life cycle, to efficiently collaborate by sharing relevant expertise and have these different contributions seamlessly integrated..."

• [August 2006] "WSDM/WS-Man Reconciliation: An Overview and Migration Guide." Version 1.0. August 2006. From IBM. See also the overview. "On March 15, 2006, HP, Intel, IBM and Microsoft announced1 the intention to reconcile the WSDM and WS-Man specifications into a single standard for management of system resources using Web services... The Service Modeling Language (SML) specification profiles how resources are to be modeled and how to represent relationships between those resources. By bringing together the 'resource manipulation' features of WSDM and WS-Man together into one specification, and agreeing on the modeling language for those resources, this effort will, in the long-run, simplify the Service Oriented Architecture landscape and accelerate the adoption of Web services based solutions... [Section 2.4. Service Modeling Language:] The Service Modeling Language, SML, specification is a set of profiles to be used to define the shape of a set of resource's information and relationships. It defines a profile of XML Schema 1.0 for content, Schematron for constraints, and Xpointer for relationships and references. A set of related SML documents are an SML model. Mapping to XML schema from existing UML type models, like CIM, has been inconsistent because the resulting XML instance documents are often not as simple or clean as they might have been if the resource had been described using XML from the beginning. Various UML profiles and models add information to the XML document to enable round trip transformation. Using the SML profiles we can model IT resources and topologies natively in XML. Basically, we think of a manageable resource as having a 'resource properties document', which implies an XML schema document describing the shape and constraints of the resource as well as an XML instance document containing its current values. In WSResourceTransfer these are called the resource document. We envision that for management, and possibly other domains, these documents describing resources and models of resources will be SML compliant. WS-CIM also creates XML schema from MOF, but it contains a lot of information for round-tripping the mapping. Over time, the WS-CIM Mapping should evolve to be SML compliant... While agreeing on the profiles in SML is important for interoperability, the true interoperability between resources and managers will be achieved when we have interoperable semantics as well. The Common Model Library (CML) will provide a set of modeling building blocks as well as very basic resource types. Note: In the Reconciled Stack Figure 2.1, SML (Resource) is situated above Core Web Service Stack (MEX) and below WS-Eventing, WS-Transfer, WS-Enumeration. [cache]

• [August 01, 2006] Service Modeling Language Announced. By Mark A. Carlson. Blog (August 01, 2006). "Sun has announced its involvement with a new management specification called the Service Modeling Language (SML). The specification itself describes a set of constructs for modeling complex IT services and their inter-relationships and dependencies. These are expressed as constraints captured in Schemas (strict subset of XML Schema) and Rules (Boolean expressions). The model is really just a set of inter-related documents describing the system or its desired state. Besides profiling XML Schema version 1.0, it also profiles Schematron for use in validating the model. SML uses XPath 1.0 with some extensions as the constraint language. A good introduction to Schematron can be found here. What this new modeling language is really good at is to describe the desired state of the dependent services that need to be provisioned and activated in the environment. The constraints allow a service provider to add their own rules about "what works with what" and what configurations of various software versions are supported and tested. This would be ideal for use in a Configuration Management DataBase (CMDB) where changes are propagated from the truth, stored as an instance of a database schema to the real world only after having been validated for correctness."

• [July 31, 2006] "Technology Leaders Release New Specification to Simplify IT Management. Common Goal to Provide Standard for Describing System Information in XML Formats." — "BEA Systems Inc., BMC Software Inc., Cisco Systems Inc., Dell Inc., EMC Corp., HP, IBM Corp., Intel Corporation, Microsoft Corp. and Sun Microsystems Inc. today announced they have published a draft of a new specification that defines a consistent way to express how computer networks, applications, servers and other IT resources are described — or modeled — in extensible markup language (XML) so businesses can more easily manage the services that are built on these resources. As a result of collaboration, the open, industry-wide specification defines a common language for expressing information about IT resources and services. Called the Service Modeling Language (SML), the specification enables a hierarchy of IT resource models to be created from reusable building blocks rather than requiring custom descriptions of every service, thus reducing costs and system complexity for customers. The group plans to submit the draft specification to an industry standards organization later this year..."

• [July 31, 2006] "Heavies Float Data Center Standard. Microsoft Leads Proposal for XML-based Model to Share Performance Information Between Disparate Resources." By Martin LaMonica. From CNET News.com (July 31, 2006). "Computing industry heavyweights on Monday announced a plan to create a standardized way for computing resources to "talk" to each other, a move they say will lower the cost of running corporate data centers. The initiative calls for the creation of an XML-based standard, called Service Modeling Language (SML), and its adoption in commercial products, including systems management software, hardware, and application development tools. The basis for SML is Microsoft's own XML specification, called Systems Definition Model. The company has already built support for SDM in Visual Studio 2005; all future management software and future operating systems will use SML starting in 2007... Ric Telford, vice president of autonomic computing at Microsoft rival IBM, said that many systems management companies, including IBM, already have projects similar to SML going on. Rather than create overlapping and competing standards proposals, the backers of SML decided to work from Microsoft's submission..."

• [July 31, 2006] "Ten Major Vendors Team Up on SML. Joining Microsoft and IBM in Work on the Draft are BEA Systems, BMC Software, Cisco Systems, Dell, EMC, Hewlett-Packard, Intel, and Sun Microsystems." By China Martens. From InfoWorld (July 31, 2006). "... All 10 vendors are publishing the draft specification on their Web sites Monday to solicit feedback from the wider IT community including customers. They plan to submit SML to a standards body before the end of this year, Tatarinov said, but have yet to determine which organization to approach. SML is based on work Microsoft began three and a half years ago on its System Definition Model (SDM), part of the vendor's Dynamic Systems Initiative aimed at simplifying complexity in users' IT infrastructure. Given its roots, Microsoft already offers some early elements of SML in its Visual Studio 2005 development tools, Tatarinov said. By next year, all of Microsoft's System Center management tools will incorporate SML. As for IBM, the first place users will be likely to take advantage of SML will be in the vendor's Rational development tools, Telford said. IBM's Tivoli systems management software will support the new language as will its IT resources such as its servers. Some of the internal work IBM did on a common language prior to getting together with Microsoft which Telford terms 'pre-SML' will begin appearing in IBM software later this year..."

• [July 31, 2006] "Announcing SML (Service Modeling Language)." By William Vambenepe (HP). Blog. "BEA, BMC, Cisco, Dell, EMC, HP, IBM, Intel, Microsoft, and Sun just published a new modeling specification called SML (Service Modeling Language). This is the next step in the ongoing drive towards more automation in the management of IT resources. The specification makes this possible by providing a more powerful way (using Schematron) to express system constraints in a machine-readable (and more importantly machine-actionable) way. It also has the advantage (being based on XSD) to align very well with XML document exchange protocols and the Web services infrastructure..."

W3C SML Working Group

On April 27, 2007 W3C announced the launch of its Service Modeling Language (SML) Working Group as part of the Extensible Markup Language (XML) Activity. John Arwe (IBM) and Pratul Dublish (Microsoft) will chair the Working Group, which is chartered through 31-October-2008 to produce W3C Recommendations for SML, adding extensions to the W3C XML Schema language for inter-document references and user-defined constraints. The first face-to-face meeting will be 11-13 June 2007 in Redmond, Washington, USA, hosted by Microsoft. The initial W3C Team Contact is Michael Sperberg-McQueen.

From the SML Working Group Charter:

The mission of the Service Modeling Language (SML) Working Group, part of the XML Activity, is to produce W3C Recommendations for Service Modeling Language by refining the 'Service Modeling Language' (SML) Member Submission, addressing implementation experience and feedback for the specifications.

SML defines extensions to the W3C XML Schema language by adding support for inter-document references and user-defined constraints. This combination of features is very useful in building complex multi-document models that capture structure, constraints, and relationships. In the management domain, these models are typically used to automate configuration, deployment, monitoring, capacity planning, change verification, desired configuration management, root-cause analysis for faults, etc. The facilities defined by this Working Group are expected to be of general use with arbitrary XML vocabularies, but the first major use of SML will be to model the structure, relationships, and constraints for complex information technology services and systems.

Several common and domain-specific models have been built using the Member Submission version of SML, and many more are under development. Further, several products and services based on SML are expected to ship in near future. In addition, SML is relevant to other standardization efforts that need SML expression of models. To meet these immediate needs, Service Modeling Language should be standardized in a timely fashion. Therefore, this Working Group shall be schedule-driven and the W3C Recommendation for SML shall remain compatible to the extent possible with the existing SML models. This charter features an aggressive schedule and a tightly constrained scope designed to ensure that the SML Working Group will meet its schedule...

The SML Working Group is chartered to standardize extensions to the XML Schema language for modeling complex services and systems. The language defines typed inter-document references, an XPath extension function for traversing inter-document references, the ability to define identity constraints across references, the ability to define rule-based constraints including Schematron (ISO/IEC 19757 - DSDL Document Schema Definition Language - Part 3: Rule-based validation - Schematron, see also the Schematron specification), an ISO standard, and to bind these constraints to types and elements...

SML must satisfy the following requirements:

1. Mechanism for specifying inter-document references for XML documents that introduce boundaries across content that needs to be treated as a unit. An inter-document reference is a link from one element to another element in a different document. The mechanism extends XML Schema to support inter-document references through XML Schema types and adds support for specifying that XML content includes inter-document references.

2. Mechanisms for specifying the following schema-based constraints on an inter-document reference type

   1. Acyclic: Instances of the reference type cannot create cycles
   2. Target must exist: The target of a reference must exist in an SML model (see 6 below for the definition of 'SML model')
   3. Constraints on the XML-Schema type of the reference's target
   4. Constraints on the element definition of the reference's target

3. Mechanism for navigation across inter-document references

4. Mechanism for identity constraints across references

5. Mechanism for associating rule-based constraints, including Schematron, with XML Schema definitions and XML documents. The expressions used for defining rule-based constraints can navigate across inter-document references

6. Multi-document validation: An SML model is a set of inter-related XML documents. Each SML model contains a special subset of documents that describe the schema and rules governing the structure and content of the model's documents. SML model validation is the process of verifying that all documents in a model are valid with respect to this special subset.

The SML Working Group is also chartered to standardize an XML document format that can be used to exchange complete or partial SML models across implementations. This document format, called the SML Interchange Format, defines:

1. An XML document format that can be used to capture the structure and semantics of a model with full fidelity so that a recipient can reconstruct the model captured in an Interchange Format document. An SML Interchange Format document captures:

   1. All or a subset of documents in a model, clearly distinguishing the subset of documents that describe the schema and rules governing the structure and content of the model's documents.
   2. Document aliases used for inter-document references
   3. Binding of XML Schema and Schematron rules to documents

The W3C Recommendation for SML should remain compatible to the extent possible with the existing SML models created using the Member Submission and offer a smooth migration path for these SML models where applicable.

The SML Working Group will use the Member Submission versions of SML and SML Interchange Format as the basis for its deliverables...

The Working Group will produce a test suite intended to promote implementation of the Candidate Recommendations, and to assess interoperability between these implementations. The Working Group may choose to deliver an SML Primer with examples. The Working Group may also choose to deliver an SML interoperability profile if needed based on Candidate Recommendation experience.

Principal References

Bibliographic citations (news/commentary) are provided below.

• W3C URIs:
  • Submission Request: Service Modeling Language (SML)
  • Service Modeling Language, Version 1.0
  • SML Interchange Format Version 1.0
  • Team Comment on Service Modeling Language (SML) Submission. By C. M. Sperberg-McQueen and Philippe Le Hégaret.
  • Acknowledged Member Submissions to W3C
• ServiceML.org:
  • Service Modeling Language (SML) Web site
  • SML Specification version 1.0
  • Service Modeling Language: Early versions
  • Interoperability Testing Workshop. See also the information from Microsoft: SML Interoperability Workshop
• Microsoft resources:
  • Service Modeling Language Specification
  • Dynamic Systems Initiative (DSI)
  • SML Interoperability Workshop. The authors of the SML and SML-IF (Service Modeling Language-Interchange Format) Specification hosted a two-day interoperability workshop on January 16-17, 2007.
• HP resources:
  • Service Modeling Language. PDF and SML Schema.
  • Cauldron: A Policy-based Design Tool. Lyle Ramshaw, Akhil Sahai, Jim Saxe, Sharad Singhal. "The paper discusses the Cauldron language, and shows how various relationships present in object-oriented models are coded using the Common Information Model (CIM) as an example. We also discuss the implementation of Cauldron, specifically as it relates to the underlying theory that enables it to generate valid configurations."
  • Automated Policy-Based Resource Construction in Utility Computing Environments. By Sahai, Akhil; Singhal, Sharad; Joshi, Rajeev; Machiraju, Vijay. See also the abstract.
  • Automated Generation of Resource Configurations through Policies. By Sahai, Akhil; Singhal, Sharad; Machiraju, Vijay; Joshi, Rajeev. See also the abstract
• IBM resources:
  • Service Modeling Language (SML) Specification
  • SML models complex IT systems
• Sun Microsystems resources:
  • Service Modeling Language (SML)
  • Service Modeling Language Announced
• Bibliographic Citations

  • Service Modeling Language Version 1.1: New Working Drafts. 2008-01-17, derived from W3C news item. Publication of the third Working Drafts.

  • "An Uncommon Update: Common Model Library (CML) Working Group Whitepaper." News on the topic of Model-based Management: The Common Model Library (CML) working group, a consortium of eleven (11) leading technology companies, released detailed plans for a CML specification based on the Service Modeling Language (SML).

  • "SML Reference Constraints." By C. M. Sperberg-McQueen. Working Draft as of 2008-01-10. An attempt to clarify the design story for the reference constraints per Inheritance of some SML reference constraints.

  • Service Modeling Language (SML). By Pratul Dublish (Principal Program Manager, Microsoft Corporation). June 2007. See the author's blog.

  • Service Modeling Language (SML). From Wiikipedia. August 2006 or later.