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Service Modeling Language 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. This charter is intended to carry SML consensus and interoperability forward, as outlined in Tips for Getting to Recommendation Faster.

Join the Service Modeling Language Working Group.

End date 31 December 2009
Confidentiality Proceedings are public
Initial Chair John Arwe (IBM)
Initial Team Contacts
(FTE %: 12.5)
Liam Quin, Henry Thompson
Usual Meeting Schedule See Meetings


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 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

    1. 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.

Success Criteria

The SML Working Group is expected to demonstrate interoperable implementations during the Call for Implementations step.

Out of Scope

Defining XML representations for modeling complex services and systems could potentially be viewed as including an endless set of technologies. To be successful, it is very important to clearly define the scope of the SML Working Group.

The following is intended to more tightly constrain the in-scope features, to prevent feature bloat and assure timely delivery. If some function, mechanism or feature is mentioned here, and it is not mentioned in the Scope or Deliverables section, then it will be deemed to be out of scope for this version.

Common and/or Domain-Specific Models

SML is a modeling language and it is not geared towards any specific models. Therefore, the SML Working Group will not define any normative common and/or normative domain-specific models. An implementation of SML may provide common and/or domain specific models to help its users in building SML models.

Interfaces for Implementations of SML

SML is not geared towards any specific implementation interfaces. Therefore, the SML Working Group will not define any interfaces for implementations of SML. In contrast, an implementation of SML may provide several interfaces for model creation, model export and import, querying a model, initiating validation, and reporting of errors encountered during validation. In addition, these interfaces may be optimized for specific programming languages, query languages, or protocols.

Query Languages

SML is not geared towards any specific query language for querying SML models. Therefore, the SML Working Group will not define or recommend any query languages for querying SML models. In contrast, an implementation of SML may support querying of SML models using suitable query languages.

Extensions to Existing Query Languages

Since SML is not geared towards any specific query language, extensions that allow existing query languages to work over linked set of XML documents are orthogonal to SML. Therefore, the SML Working Group will not define any such extensions to existing query languages. However, an implementation of SML may want to use existing query languages (such as XQuery) for supporting querying of SML models which may be composed of multiple documents with inter-document links between them. Such an implementation may need to define extensions to the query language to support queries over sets of linked XML documents.

Interfaces and Protocols for SML Model Exchange

SML is not geared towards any specific interface and/or protocol for model exchange. Therefore, the SML Working Group will not define any interfaces and/or protocols for exchanging SML models. However, an implementation of SML may provide interfaces and/or protocols for exchanging SML models with other implementations or between separate instances of itself.

Alternate Representations of SML Models

The SML Working Group will focus on providing an XML Information Set representation of SML models and will not focus on mapping to or reconciling with other approaches for modeling. Alternative representations of SML models or alternative approaches for modeling may be important for External Groups, other W3C Working Groups and Activities, and are delegated to those groups.


New publications and Milestones

  • A W3C Recommendation for the Service Modeling Language 1.1

  • A W3C Recommendation for the Service Modeling Language Interchange Format 1.1

List of deliverables and their milestones
Note: The group will document significant changes from this initial schedule on the group home page. The Advisory Committee MUST be notified of any significant schedule changes.
Specification FPWD LC CR PR Rec
Service Modeling Language March 2009 May 2009
Service Modeling Language Interchange Format March 2009 May 2009

Other 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

  • an SML interoperability profile if needed based on Candidate Recommendation experience

  • a note about possible future directions for SML and SML-IF after these two specifications have become W3C Recommendations

Timeline View Summary


W3C Groups

The SML Working Group should coordinate its efforts with other Working Groups involved in the XML Activity, especially the XML Schema Working Group, since the SML is based on XML Schema, and the XML Query Working Group.

As part of the XML Activity, the SML Working Group Chair and Team Contact will be represented in the XML Coordination Group.

Furthermore, Service Modeling Language Working Group expects to follow these W3C Recommendations:


Effective participation is expected to consume one or two workdays per week for each Working Group participant; two or more days per week for editors. The Chair shall ensure that the criteria for Good Standing are understood and followed.

To be successful, we expect the SML Working Group to have 6 or more active participants for its duration.

Participants are expected to carry out their assignments in a timely fashion, attend most meetings, and to remain familiar with group documents and mailing list discussion (W3C Process Document, section Active participation will help ensure rapid progress.

The Chair is expected to use the means provided by the W3C Process to help the SML Working Group remain on schedule and avoid scope creep (see the list of expected milestones). The Chair will:

  1. Ensure that, when setting the agenda, discussion items are within the scope of the chartered deliverables.

  2. Ensure issues are decided in a timely fashion, after due consideration of all opinions and positions.

  3. Reconsider a decision only when presented with new information. (W3C Process Document, section 3.3.4).

  4. Ensure frequent publication of Recommendation Track documents (W3C Process Document, section 6.2.7).


The SML Working Group will have distributed and face-to-face meetings.

At least up until the Last Call period ends a two-hour Working Group distributed meeting will be held every week. Thereafter, a one and half hour Working Group distributed meeting will be held every week. When necessary to meet agreed-upon deadlines, distributed meetings may be held twice a week. Face-to-face meetings are expected to occur every 2 to 3 months (three or four meetings per year).

The SML Working Group may adjust the timing and duration of meetings to address the workload and assure that the goals and schedule of this charter are achieved.


This group primarily conducts its work on the public mailing list public-sml@w3.org. A Member-only mailing list member-sml@w3.org is also available for administrative purposes.

Information about the group (deliverables, participants, face-to-face meetings, teleconferences, etc.) is available from the SML Working Group home page .

Decision Policy

As explained in the Process Document (section 3.3), this group will seek to make decisions when there is consensus. When the Chair puts a question and observes dissent, after due consideration of different opinions, the Chair should record a decision (possibly after a formal vote) and any objections, and move on.

When deciding a substantive technical issue, the Chair may put a question before the group. The Chair must only do so during a group meeting, and at least 50% of participants in Good Standing must be in attendance. When the Chair conducts a formal vote to reach a decision on a substantive technical issue, eligible voters may vote on a proposal one of three ways: for a proposal, against a proposal, or abstain. For the proposal to pass there must be more votes for the proposal than against. In case of a tie, the Chair will decide the outcome of the proposal.

Patent Policy

This Working Group operates under the W3C Patent Policy (5 February 2004 Version). To promote the widest adoption of Web standards, W3C seeks to issue Recommendations that can be implemented, according to this policy, on a Royalty-Free basis.

For more information about disclosure obligations for this group, please see the W3C Patent Policy Implementation.

About this Charter

This charter for the SML Working Group has been created according to section 6.2of the Process Document. In the event of a conflict between this document or the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Henry Thompson, Staff Contact
Liam Quin, XML Activity Lead and alternate contact

$Date: 2009/03/12 16:59:49 $