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The principal goal of this document is to help W3C Working Groups to write clearer, more implementable, and better testable technical reports. It both provides a common framework for specifying conformance requirements and definitions, and also addresses the representation of specifications (technical reports) as schemata, both of which facilitate the generation of test materials. The material is presented as a set of organizing guidelines and verifiable checkpoints. This document is one in a family of Framework documents of the Quality Assurance (QA) Activity, which includes the other existing or in-progress specifications: Introduction; Operational Guidelines; and, Test Guidelines.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.
This document is a W3C Working Draft (WD), made available by the W3C Quality Assurance (QA) Activity for discussion by W3C members and other interested parties. For more information about the QA Activity, please see the QA Activity statement.
While keeping most of the principles behind the second published working draft, this third version has re-ordered the guidelines in a more logical way, and takes a more formal approach in the design of checkpoints, where every checkpoint has a set of test assertions. It integrates all the issues resolutions agreed during the QA WG Tokyo face-to-face meeting and the weeks following. A more detailed changelog is available below.
This version supersedes all previous drafts. It is expected that updated versions of this document will be produced regularly, along with other members of the Framework documents family. It is anticipated that the next public version of this document will be the Last Call version (estimated, February 2003).
This document is accompanied by a QA Framework: Specification Examples & Techniques document, which illustrate the guidelines and checkpoints with case studies, and explain how to satisfy the checkpoints.
The QA Working Group Patent Disclosure page contains details on known patents related to this specification, in conformance with W3C policy requirements.
Please send comments to www-qa@w3.org, the publicly archived list of the QA Interest Group [QAIG]. Please note that any mail sent to this list will be publicly archived and available. Do not send information you would not want to see distributed, such as private data.
Publication of this document does not imply endorsement by the W3C, its membership or its staff. This is a draft document and may be updated, replaced, or made obsolete by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress".
A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.
An appendix to this document [SPEC-CHECKLIST] presents all checkpoints in a tabular form, for convenient reference.
The principal goal of this document is to define a framework to assist the W3C Working Groups (WGs) in writing specifications that:
Within this Specifications Guidelines document, the term "specifications" is specifically limited to W3C Technical Reports, even though these guidelines could be used along other documents.
This document describes what goes into the specification with respect to conformance and conformance topics, followed by rules for specification anatomy that should facilitate test development as well as produce better, more testable specifications.
The set of checkpoints as a whole has been written in anticipation that the checkpoints are being applied to new, in-development specifications. It is not expected that existing specifications that pre-date these guidelines will be able to satisfy all checkpoints as they are stated. Many legacy specifications may indirectly comply with the spirit or intent of some checkpoints, without actually satisfying all requirements in those checkpoints.
The target audience of these specification guidelines is:
It is a design goal of these guidelines the WGs can apply them in a common-sense and workable manner.
Good specifications lead to better implementations and foster the development of conformance test suites and tools. Conforming implementations lead to interoperability.
The quality of the specification has direct impact on the quality of implementations. Quality encompasses utility which refers to the usefulness of the specification to the intended users and objectivity which focuses on the whether the specification is presented in an accurate, clear, complete, and unbiased manner.
Providing requirements and definitions about conformance topics, as well as guidance in the structure and anatomy of specifications, will foster a mutual understanding amongst developers of specifications, implementations, and conformance test materials. Specifically, well-structured specifications with clear and comprehensive conformance requirements:
This document is part of a family of QA Framework documents designed to help the WGs improve all aspects of their quality practices. The QA Framework documents are:
The QA Framework documents are interrelated and complement each other. For example, the anatomy of a specification is related to the type of test materials that will be built, hence there is interrelationship between this document and the Test Guidelines. The reader is strongly encouraged to be familiar with the other documents in the family.
The Framework as a whole is intended for all Working Groups, as well as developers of conformance materials for W3C specifications. Not only are the Working Groups the consumers of these guidelines, they are also key contributors. The guidelines capture the experiences, good practices, activities, and lessons learned of the Working Groups and present them in a comprehensive, cohesive set of documents for all to use and benefit from. The objective is to reuse what works rather than reinvent and to foster consistency across the various Working Group quality activities and deliverables.
This document does not preclude the need to apply the W3C Manual of Style [STYLE-MAN] and to conform to the Publication Rules [PUBRULES ] (member-only). It is intended to complement those specifications.
This document employs the WAI (Web Accessibility Initiative) model for representing guidelines or general principles for the development of conformance materials. See, for example, Web Content Accessibility Guidelines 1.0 [WCAG10]. Each guideline includes:
The checkpoints in each guideline define specification characteristics and requirements needed to fulfill the purpose of the guideline. Each checkpoint definition includes:
Each checkpoint is intended to be specific enough so that someone can implement the checkpoint as well as verify that the checkpoint has been satisfied. A checkpoint will contain at least one, and may contain multiple individual requirements , that use RFC2119 normative keywords. See the "Conformance" chapter for further discussion of requirements and test assertions.
A separate appendix to this document [SPEC-CHECKLIST] presents all checkpoints in a tabular form, for convenient reference. This is an Implementation Conformance Statement (ICS) pro-forma for this specification. (See GL12.)
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY ", and "OPTIONAL" will be used as defined in RFC 2119 [RFC2119]. When used with the normative RFC2119 meanings, they will be all upper case. Occurrences of these words in lower case comprise normal prose usage, with no normative implications.
Unusual terms in these framework documents are defined when first used. This document contains a "Definitions" chapter. Generally useful QA-specific terms will eventually be in the QA Glossary [QA-GLOSSARY]. If terms are in the QA Glossary, their definition herein will refer to that QA Glossary entry with a link. The definitions herein may supplement or build on that generic definition with other information that is useful or helpful in the specification guidelines context. They will not contradict the generic definitions.
Some checkpoints are more critical than others for producing a high quality, testable standard that is a sound basis for successfully interoperable products. Therefore each checkpoint is assigned a priority level based on the checkpoint's impact on the quality of the specifications produced by the Working Groups.
There are 14 guidelines:
The guidelines are of two general types:
Each of the latter set of eight guidelines GL2 through GL9 addresses a way in which the conformance policy of a specification might allow variation amongst conforming implementations. For example, a specification might allow implementations to choose between one of two well defined behaviors for a given functionality, thus two conforming implementations might vary on that aspect.
For this reason, these eight guidelines are collectively called the "dimensions of variability (DoV)". The eight dimensions of variability recognized by this document are:
The above are not necessarily all orthogonal to one another. There are many possible associations, dependencies, and interrelationships. As a general policy, these specification guidelines do not attempt to legislate correct or proper relationships amongst the DoV. Rather, they try to clarify the nature of each dimension, and require specification to make deliberate and well documented choices. Some discussion of possible interrelationships, including examples will be found in the Specification Examples & Techniques.
The dimensions of variability are one of the principal concepts in this guidelines document to help organize, classify and assess the conformance characteristics of W3C specifications. The eight DoV get special attention because, since they are at the core of the definition of a specification's conformance policy, there is significant potential for negative interoperability impacts if they are handled carelessly or without careful deliberation.
As a general principle, variability complicates interoperability.. In theory, interoperability is best when there are numerous identical, complete, correct implementations. However, in practice, the net effect of conformance variability is not necessarily negative in all cases, when compared to the alternatives. For example profiles — subdivisions of the technology targeted at specific applications communities — introduce variability amongst implementations. Some will implement Profile ABC, some will implement Profile XYZ, and the two might not intercommunicate well if ABC and XYZ are fairly different. However, if ABC and XYZ are subsets of a large monolithic specification — too large for many implementors to tackle in -- and if they are well targeted at actual application sectors, then subdivision by profiles may actually enhance interoperability.
Different sorts of variability have different negative and positive impacts. The principal danger is "excessive" variability - variability which goes beyond that needed for positive interoperability trade-off, and which unnecessarily complicates the conformance landscape.Specification writers need to carefully consider and justify any conformance variability allowed, do so by reference to the project requirements and use cases, and explicitly document the choices made.
When writing specifications it is critical to understand their primary purpose and scope. Clearly defined scope helps to keep the specification content focused and unambiguous.
If the specification describes content requirements (for example, [WCAG10], [UAAG10]), understanding of their purpose is the key to defining the minimal sufficient set. If the specification describes a protocol or Application Programmer Interface (API) — examples include XML Protocol, DOM -- there should be a clear understanding of the primary use cases. For the purposes of this document, a use case is a specification mechanism or technique that captures the ways a specification would be used, including the set of interactions between the user and the specification as well as the services, tasks, and functions the specification is required to perform.
Readers of the specification face similar difficulties to writers. To understand what the document says, the reader needs to know the context of the author, and the scenarios the author had in mind. In case of protocols and APIs specifications developers try to assess whether the specifications cover the use cases the product needs to cover. Having no use cases described in the specification invites misuse of the specification itself.
To fulfill this checkpoint, a specification MUST define what scenarios are in scope and SHOULD identify out of scope scenarios.
Rationale: it helps both the writer and the reader to know what are the limits of what is specified in a normative document.
Examples & Techniques for this checkpoint.
A User Scenario is an instance of a use case, representing a single path through the use case. Thus, there may be a scenario for the main flow through the use case and other scenarios for each possible variation of flow through the use case (e.g., representing each option).
To fulfill this checkpoint, a specification MUST include or link to User Scenarios, SHOULD have an extensive list of the user scenarios that the authors have in mind
Rationale: User scenarios help to assess what features are missing and what features are superfluous in the specification.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST include or link to at least one example and SHOULD provide an example for each section that public feedback has shown to be unclear or hard to understand.
Examples & Techniques for this checkpoint.
A formal description is a concrete or abstract representation of an intended behavior in the specification.
To fulfill this checkpoint, a specification MUST provide an example for each identified formal description.
It is hard to understand the formal descriptions of content without informative interpretations.
For instance, the recent complex specifications like XML Schema [XML-SCHEMA] and XML Protocol have shown the interest of having a "Primer" part or section to illustrate how to use the specification.
Examples & Techniques for this checkpoint.
Categorizing the specification provides a basis for classifying the software that may be affected by the specification — and thus, provides the answer to "what needs to conform?". To answer this question, it helps to look at the nature of the specification and categorize it. Most specifications can be classified into one of the following categories:
The categories indicate what the specification describes. One specification could potentially fall into more than one category.
From this categorization of specifications, the WG can identify the class of products that are affected by the specification. Classes of products can be generalized as either or producers or consumers, or as content itself. Identifying which are producers and consumers is clear for a protocol-type specification, the two parties to the dialog are the targets. For a processor-type specification, the processor is the consumer of an XML vocabulary defined in the specification. For content-type specifications, there may be one or more consumers that take the content and 'play' it in some way.
The following is a non-exhaustive list of classes of products for W3C specifications.
One specification could define more than one player. For example, MathML could address the behavior of display of math notation and also a consumer that parses the MathML as a formula and uses it for mathematical processing.
The conformance clause identifies the "class of products" (i.e., object of the claim) that is the target of the specification. In addition to identifying what conforms (i.e., class of products), it describes how conformance can be met. This would be a description of the conformance requirements, conditions and/or criteria for each class of product.
To fulfill this checkpoint, a specification:
Example. Within the SMIL 2.0 Language Profile ([SMIL20], chapter 13), there are 2 classes of products: documents and basic user agents. Within Mathematical Markup Language (MathML) 2.0 [MATHML20] there are output-compliant, authoring tools and input-compliant, rendering/reading tools.
Examples & Techniques for this checkpoint.
The conformance requirements indicate the conditions to be satisfied in order to claim conformance. It is likely that these conformance definitions will reference normative text within the specification or in other related specifications.
To fulfill this checkpoint, a specification MUST define the conformance requirements for each class of product.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST identify in the Introductory section which of the types of object are specified in the document as a whole.
Rationale: doing so helps keep the scope of the specification in focus, both for the reader, and for the author(s) who must define the classes of product and their conformance criteria.
Some specifications define more than one of the enumerated object types. XForms is an example. It defines: Content, via an XML vocabulary; Content, via named datatypes; Syntax, in the form of a set of functions to supplement the XPath core set; behavior of a processor; behavior of a user agent; a set of events.
Examples & Techniques for this checkpoint.
A look at various W3C Technical Reports shows that the term "conformance" is often qualified, resulting in more than one type of conformance. It is important to convey an understanding of what is meant by conformance and where the products of a class are allowed to have more, less, or different functionality from one another. If the specification defines behavior for more than one class of product, there may be a separate conformance policy for each class. Often, the specification will allow discretionary choices, such as the choice of date-time formats, but require a conforming product to make a choice only within the allowable range. (See Guideline 8 for more discussion.)
Sometimes a product developer can choose to implement certain modules. There may be per-module conformance requirements that apply if and only if the developer chooses to implement a particular module.
Sometimes a product developer can choose to implement extensions. There may be conformance requirements for non-interference of extensions. (See Guideline 9 for more discussion.)
Where all products of a class must be substantially alike, it should be clear that a "strict conformance" policy is in effect for that product class.
Strict conformance is defined as conformance of an implementation that employs only the requirements and/or functionality defined in the specification and no more (e.g., no extensions to the specification are implemented). No discretion is granted to implementers, and any requirements for handling deprecated features must be followed.
Overall, the intent of the WG should be clear. In particular, a reader intending to implement a product in one of the product classes addressed by the specification should know what the WG wants for interoperability among products in the class. The developer should understand what forms, if any, of "product differentiation" are allowed among conformant products. The specification may need to explain how the rules apply and possibly provide examples.
Guideline 10, "conformance clause" is related to this guideline. This Guideline 3 focuses on the establishment and scope of definition of a conformance policy, while Guideline 10 focuses on where and how to document it. That is, the verification of these checkpoints will require looking at the Conformance Clause.
To fulfill this checkpoint, a specification MUST include a normative section detailing any universal requirements for minimum functionality. It is not applicable if there are not any universal requirements.
Rationale: the reader must be able to recognize any minimum that applies to all conforming products of each class. The test suite can have a core of universal test cases.
If levels are used (see Guideline 6), the lowest level may represent the minimum set of requirements. If profiles are used (see Guideline 4), there may be different minima for each profile. If modules are used (see Guideline 5), there may be different minima for each module. Furthermore, a module may itself be a minimum (i.e., required) for a particular class of product.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST state in its conformance section if the conformance requirements are strict or identify the kinds of variability that are permitted..
Rationale: the reader must be able to recognize when a policy of "strict conformance" applies. As defined above, this implies that all conformant products of a class behave essentially the same way.
Strict conformance can apply separately to each class of product addressed by the specification. If profiles are used, each profile may have its own conformance boundaries. If modules are used, each module may have its own conformance boundaries. Some profiles or modules may have a strict conformance policy while others do not.
Use the definition provided above (or in the QA Glossary [QA-GLOSSARY]). The definition may be modified to
adjust its scope, for example when applying it to modules, profiles or
levels. In such cases, the scope of requirements [...] defined in the
specification
is narrowed from specification to the module, profile, or functional level that is the target of the statement.
Examples & Techniques for this checkpoint.
To full this checkpoint, a specification MUST state in its conformance section all facets of the requirements where the required features represent the maximum allowable capabilities.
Rationale: When a strict conformance policy applies, the maximum set of features is the same as the minimum. When strict conformance does not apply, implementations may be allowed to exceed the specified capabilities in ways other than having extensions. (Example: a graphical capability may be specified with a required resolution or a set of resolution levels that must be supported. The specification may wish to require that implementations not create images of higher resolution due to concerns about excessive size.) The specification should identify the facets in which an implementation may add more features, if there is a history of expanding features for those facets.
If profiles are used (see Guideline 4), state whether extra capabilities of the platform may be exploited. If modules are used (see Guideline 5), there may be different provisions for extra features applying to each. If levels are used (see Guideline 6), state whether the highest level may be exceeded with additional features or functionality. If deprecation applies (see Guideline 7), make it clear whether support of the obsolete features is optional, part of a level, or required. If levels are used (see Guideline 6), make it clear whether the highest level may be exceeded with additional features or functionality. If discretionary choices are allowed (see Guideline 8), make it clear if more than one may be implemented, when it is technically possible to do so.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST either exclusively use conformance terms as defined in this document or define any other conformance terms used in it and reference them from the conformance clause.
Rationale: it is necessary to define terms that govern application of the conformance provisions. Ideally, all terms are from QA documents and other existing literature and need only be cited. If special terms are constructed, such as to combine modules and levels or modules and discretionary choices, they need to be defined in the specification.
Examples & Techniques for this checkpoint.
A profile is a subset of the technology that supports a particular functional objective or a subset of a set of technologies defining how they are required to operate together (e.g., XHTML plus MathML plus SVG).
Profiles can be based on hardware considerations associated with target product classes — for example, SVG Tiny is aimed at mobile phones — or they may be driven by other functional requirements of their target constituencies — for example, a graphical profile tailored for technical illustrations in aircraft maintenance manuals.
The use of profiles to divide the technology is described in the specification, and may or may not be reflected and paralleled by the structure and organization of the specification.
Specifications may define individual profiles, or may define rules for profiles, or both. An individual profile defines the requirements for classes of products that conform to that profile. Rules for profiles define validity criteria for profiles themselves — i.e., if others (users, applications, or other standards) define their own profiles of the standard, then rules for profiles define the constraints that those profiles must satisfy in order to be considered valid profiles of the specification.
For example, XHTML Modularization ([XHTML-MOD], section 3) and Synchronized Multimedia Integration Language (SMIL 2.0), [SMIL20] specifications both define rules for profiles -- what constraints must a profile meet in order to be classified as a "Host Language Profile" or an "Integration Set Profile." SMIL further defines some specific profiles, using the modularization. Separate recommendations -- XHTML Basic [XHTML-BASIC] and XHTML 1.1 [XHTML11] — define specific profiles based on the XHTML modularization.
To fulfill this checkpoint, a specification
It is not applicable if profiles are not used.
For example, is content required to conform to one of the profiles, or is there a concept of conformance of content independent of conformance to one of the profiles? Is a producer (of content) conforming if it generates content that is otherwise valid but does not conform to a profile?
Note: If there is a "full" profile defined — for example, incorporating all of the defined functionality of the specification, including extensibility features — then any valid content, as well as any correct producers and fully capable consumers, might seem to be automatically using that profile. However, profiles (e.g., of content) often include self-identification requirements, and these would have to be observed for conformance of valid content to even a "full" profile.
An example of additional conditions on profiles would be to require that only one profile can be implemented at a time.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST define for each profile the minimal required features/support for each class of product. It is not applicable if profiles are not used.
Rationale: because a profile places explicit requirements on each class of product that have specific and often limited operating environments these requirements must be defined for each class of product that is affected.
To illustrate, SMIL 2.0 [SMIL20] has a SMIL 2.0 Language Profile for user agents but also provides a SMIL 2.0 Basic Profile for wireless and embedded devices. The SMIL 2.0 Language Profile requires that a user agent implement the BasicAnimation module but not the SplineAnimation Module. The SMIL 2.0 Basic Profile on the other hand does not require implementation of any of the Animation modules.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST identify all the relations and interactions between profiles and the other dimensions of variability. It is not applicable if profiles are not used.
Dependency or interrelationship between profiles and modules is common -- XHTML [XHTML-MOD], SMIL [SMIL20], SVG 1.1 [SVG11]. Less often, deprecated features, levels, discretionary choices, or extensions could depend on profiles.
Examples & Techniques for this checkpoint.
if the specification allows the creation of derived profiles, to fulfill this checkpoint a specification MUST provide requirements for derived profiles and these requirements MUST be testable. It is not applicable if profiles are not used.
It is RECOMMENDED that requirements for derived profiles impose at least these two rules on derived profiles: derived profiles SHOULD be specified in a way that meets all the pertinent checkpoints of this document (QA Framework: Specification Guidelines); and, derived profiles SHOULD NOT contradict pre-defined profiles, if there are any in the base specification.
Rationale: well-designed rules for profiles will facilitate that derived profiles are well-specified, and testability will enable an independent tester to verify conformance of a derived profile to the rules.
Examples & Techniques for this checkpoint.
Modules are non-hierarchical, discrete divisions or functional groupings of the technology.
For example, SMIL 2.0 [SMIL20] defines a module as follows:
A module is a collection of semantically-related XML elements, attributes, and attribute values that represents a unit of functionality. Modules are defined in coherent sets.
Modules generally can be implemented independently of one another — e.g., audio vs. video module. That notwithstanding, it is possible for one module's definition (and therefore implementation) to have explicit dependency upon another module. It is not only possible, but common to implement multiple modules.
To fulfill this checkpoint, a specification MUST document any mandatory conditions or constraints on their usage. Such conditions include,
It is not applicable if modules are not used.
The conditions or constraints normally will be tailored according to class of product.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST specify any relationships and interaction with other dimensions of variability. It is not applicable if modules are not used.
Rationale: often there is dependency or interrelationship among modules, on the one hand, and profiles or discretionary choices on the other. Modules may have levels or deprecated features. Extensions could be defined based on modules.
Examples & Techniques for this checkpoint.
Functional levels — or in common usage, simply "levels" — are used to group functionality into nested subsets, ranging from minimal or core functionality to full or complete functionally. Level 1 is the minimum or core of the technology. Level 2 includes all of level 1 plus additional functionality. This nesting continues until level n, which consists of the entire technology.
Levels may result from progressive historical development and enrichment of the technology in a series of specifications, as in the case of CSS and DOM. Levels could also be defined explicitly in a single edition of the specification, but no examples of this are found in W3C specifications. Rather, it is more common in current W3C practice to use profiles to accomplish this. For example, SVG Mobile [SVG-MOBILE] defines three nested profiles — Tiny, Basic, Full — which are each targeted at a specific graphics hardware community (mobile phone, hand-held computer, desktop computer).
See Guideline 4 for full discussion of profiles, including comments on possible profiles-levels relationships. See Guideline 6 for a full discussion of modules, including possible modules-levels relationships.
To fulfill this checkpoint, a specification MUST specify any relationships and interaction with other dimensions of variability. It is not applicable if levels are not used.
Levels can be dependent on, or apply to, modules. Less often, there can be a relationship between levels, on the one hand, and profiles or deprecated features on the other.
Examples & Techniques for this checkpoint.
A deprecated feature is a feature whose use is discouraged because it has been outdated by newer constructs or is no longer viable.
After the initial publication of a specification, specification developers may consider the deprecation of a feature (e.g., function argument, element or attribute) defined in the specification. Deprecated features may become obsolete and no longer defined in future versions of the specification. Deprecation of a feature may warn implementers that the feature was a bad idea and it may be withdrawn in the future. Specification developers need to consider the effect of deprecation on all the classes of products that implement the specification (e.g., authoring tools, user agents) as well as the conformance consequences on each class of product. For the purpose of backward compatibility, it may be necessary to specify different requirements for the support of deprecated features for each class of product. For example, authoring tools (producers) would not use the feature, but user agents (consumers) would continue to support it.
To fulfill this checkpoint, a specification MUST identify in a normative section each deprecated feature. It is not applicable if there is no deprecated feature.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST specify the degree of support required for each deprecated feature for each product class and the conformance consequences of the deprecation. It is not applicable if there is no deprecated features.
For example, a deprecated-features section of MathML 2.0 ([MATHML20], section 7.2.1.2) describes, about deprecated MathML 1.x features, that MathML-output-compliant authoring tools may not generate MathML markup containing deprecated features; whereas MathML-input-compliant rendering/reading tools must support deprecated features.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST document each deprecated features with a rationale for deprecation. It is not applicable if there is no deprecated features.
Rationale: providing the rationale for deprecating a feature helps implementers and users to understand the motivation for the deprecation, the impact and consequences on current and future implementations, and perhaps insight into its eventual disappearance from the specification.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide an example for each deprecated feature showing how to avoid using it. It is not applicable if there is no deprecated features.
Rationale: examples are helpful in providing alternatives or better ways to get the same results. By showing what can be done in place of the deprecated feature will help to get implementers to discontinue use of the deprecated feature.
Examples & Techniques for this checkpoint.
Discretionary items are defined as deliberate and explicit grants of discretion by the specification, to the implementations, that describe or allow optionality of behavior, functionality, parameter values, error handling, etc.
Discretionary items are often made available in specifications, to give implementers of the technology the opportunity to decide from alternatives when building applications and tools. Discretionary items may be considered necessary because of environmental conditions (e.g., hardware limitations or software configuration, or external systems), locality (e.g., time zone or language), optional choices providing flexibility of implementation, dependence on other specifications, etc.
Discretionary items come in three basic variants:
To fulfill this checkpoint, a specification MUST indicate the rationale for the discretionary items by providing a reference or link to its use cases and/or project requirements and SHOULD identify by labeling all discretionary items. It is not applicable for specifications that don't have discretionary items.
Doing this helps readers, implementers and testers to find these discretionary items and understand the need for them.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST describe any permitted variations or constraints for how the implementation dependency is realized by implementations.
Examples of permitted variations or constraints to be addressed include:
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST indicate whether zero, exactly one, or a multiple of choices/options are allowed to be implemented. It is not applicable for specifications that don't use discretionary items or for implementation dependent values among them.
Examples of constraints include mandating that an implementation implement only one choice, implement every choice, or be allowed to implement none of the choices.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, the specification MUST state that given identical conditions, the effect of a discretionary choice is consistent within a single implementation.
Rationale. Users have an expectation of what to expect and should be able to count on getting the same results under the same conditions with a given implementation.
Examples & Techniques for this checkpoint.
An extension to a specification is a mechanism to incorporate functionality beyond what is defined in the specification.
Allowing extensions affects how conformance is defined as well as what conformance claims can be made. Exercise caution in determining the extent to which extensions are allowed or not allowed. Since extensions can seriously compromise interoperability, specification writers should carefully consider whether extensions should be allowed.
Extensions may be private (often vendor specific) or public (a full description of the extension is public). Private extensions are usually truly private, i.e., valid for a specific implementation or are only known by prior agreement between implementations. Public extensions are extensions in which the syntax, semantics, identifiers, etc. are defined and published allowing anyone to implement the extended functionality.
Specifications allow extensions for various reasons. Extensions allow implementers to include features that they consider to be required by their customers. Also, extensions, often define new features that may migrate into future versions of the specifications. However, the use of extensions can have a severe negative impact on interoperability. Some methods for enabling extension have less impact on interoperability than other methods. For example, a specification that allows private extensions (e.g., proprietary) is highly likely to impede interoperability, whereas a specification than permits only registered extensions partially mitigates the negative impacts.
To fulfill this checkpoint, a specification MUST state that extensions are disallowed and MUST indicate the conditions for when this holds true.
Rationale: if the specification writer wants to enhance interoperability by constraining implementer extensions, wording in the specification must indicate this.
If extensions are not allowed, then it should be clear to the reader that not only are extensions not allowed, but the circumstances under which they are not allowed. This is strict conformance. Strict conformance is often imposed on applications or content (e.g., a software program or document instance). This prohibition of extensions could be applied to a specific profile or module, rather than to the entire specification.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST state
and MUST document the rationale for allowing extensions by referencing use cases and/or project requirements. It is not applicable if the specification doesn't allow extensions.
Rationale: readers should be able to understand the motivation for the inclusion of an extension and its intended use. Documenting the scope and rationale for extensions helps assess the impact of extensions on interoperability
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, the specification MUST state that extensions can not negate or change support for required functionality. It is not applicable if extensions are not allowed.
Requirements in the specification can not be compromised or contradicted by adding extensions.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide a standard way of defining the extension. It is not applicable if extensions are not allowed.
This helps to ensure predictable handling of extensions, that is, its recognition as such and the appropriate actions (i.e., to ignore or to implement).
Examples & Techniques for this checkpoint.
To fulfill this checkpoint a specification MUST require that the syntax and semantics of the extension be publicly documented. It is not applicable if extensions are not allowed.
Rationale: public availability with a full description allows the extension to be implemented by anyone without prior arrangement. This enhances interoperability by allowing the same functionality to be uniformly implemented across different implementations.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST indicate via conformance requirements that implementations provide a mode under which they produce only conforming content. This checkpoint is not applicable if extensions are not allowed.
Rationale: This checkpoint can be used to ensure that there is a way to produce (generate) only conforming content. It is applicable to specifications that identify producer of content as one of its classes of products.
Examples & Techniques for this checkpoint.
A conformance clause is a part or collection of parts of a specification that defines the requirements, criteria, or conditions to be satisfied by an implementation or application in order to claim conformance. Typically the conformance clause is a high-level description of what is required of implementations and applications.
Guideline 3, "conformance policy" is related to this guideline. Guideline 3 focuses on the establishment and scope of definition of a conformance policy, while this Guideline 10 focuses (among other topics) on how and where to document it.
To fulfill this checkpoint, a specification MUST document its conformance policy and specific conformance requirements.
As used in this checkpoint, "clause" does not necessarily imply a specific single document section or location (see next checkpoint).
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST document its conformance policy and specific conformance requirements in a dedicated section of the document.
Rationale: having the conformance clause exist as a separate section within the specification makes it clearly identifiable, allowing a reader to find the overall conformance policy, as well as all specific conformance provisions from a single starting point.
Examples & Techniques for this checkpoint.
A specification depends on another specification when it relies on or requires functionality (or behavior) from the other specification in order to work (function) correctly. This other specification provides a necessary condition or functionality.
To fulfill this checkpoint, a specification MUST have normative references to any specification it depends on and MUST describe the relationship between the specifications and any conformance implications
Rationale: dependence on other specifications affects the conformance boundaries of the current specification, and thereby affects the requirements on conformant products.
The linking parts of the Manual of Style ([STYLE-MAN], section 11.5.1) describe the recommended way of citing an external reference from the prose of a specification, as well as how to construct an entry in its References section.
For example, SVG 1.0 requires that the class of product called "user agent" be consistent with the XML 1.0 Recommendation [XML10] and (conditionally) support Cascading Style Sheets, level 2 [CSS2].
Examples & Techniques for this checkpoint.
A specification may differentiate conformance claims by designating different degrees or types of conformance in order to apply and group requirements according to modules, profiles, levels, or priorities. When a conformance claim is linked to functionality, impact and/or incremental degrees of implementation, the term 'conformance level' is often used to indicate the varying degrees of conformance. The WG includes in the specification the way they want people to claim their conformance.
To fulfill this checkpoint, a specification MUST identify and define all conformance designations.
In current W3C practice, a number of different naming conventions are used to label conformance, in cases where there is not a single, monolithic (strict) conformance definition. The naming convention used to label the conformance can provide useful information. Degrees, for example, implies incremental importance or difficulty. This Specification Guidelines document uses "degrees" for example, to refer to three successively more demanding degrees of conformance (A, AA, AAA).
Commonly used conformance designations include categories, degrees, and levels. Use of "conformance levels" is discouraged in new specifications, because of the potential for confusion with "functional levels".
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide specific wording of the claim and the specific wording MUST at least include the specification name, its version, the conformance level satisfied and information about the subject that which is claiming conformance and the date of the claim.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide a conformance disclaimer.
Rationale: although it is possible to prove with certainty when something does not conform, the reverse is not necessarily true. Especially for functional specifications, where a claim goes beyond syntax testing, a claim of conformance is not a guarantee that the claimant is 100% conforming with the specification. A disclaimer can help clarify the meaning of a conformance claim as well as its limitations. For example, this document contains a conformance disclaimer.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST NOT include any restriction about who can make a claim nor where claims can be published.
Claimants (or relevant assuring parties) are solely responsible for the validity of their claims, keeping claims up to date, and proper use of the conformance icons.
Examples & Techniques for this checkpoint.
An Implementation Conformance Statement (ICS) provides a mechanism whereby a supplier of an implementation of the specification provides information about the implementation in a standardized manner. It is used to indicate which capabilities and options have been implemented, as well as the limitations of the implementation. An ICS usually takes the form of a questionnaire where product implementors report on the conformance of their product to the named specification.
An ICS is useful in disclosing optional functionality and discretionary behavior and values. The results of the ICS can be used to identify the subset of test cases from a conformance test suite that are applicable to the implementation to be tested. This will allow the implementation to be tested for conformance against only the relevant requirements.
The basic and detailed information that an ICS provides can also be used to assess and deduce the interoperability potential of two or more products.
To fulfill this checkpoint, a specification MUST either:
Rationale: the inclusion of an ICS may not be applicable to all specifications. A specification's ICS can be thought of as providing a minimal list of items supported by the implementation, capturing information the WG deems necessary to support conformance claims.
An ICS that is part of a specification does not preclude other organizations such as certification organizations, from having their own ICS.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST include the ICS as part of its conformance claim requirements. This checkpoint is not applicable, if an ICS is not included in the specification.
Rationale: the ICS is coupled with the requirements for making a conformance claim (guideline 11), thus providing specific information about the implementation and substantiating the conformance claim.
Examples & Techniques for this checkpoint.
There is a lot to be said for consistency and clarity within a document - it facilitates the understanding and comprehension of the document. Authors and editors of specifications should already be familiar with the W3C Manual of Style [STYLE-MAN] and Publication Rules (member-only) [PUBRULES], which help to achieve this. With respect to conformance, it is important to provide clear and unambiguous statements, so that the reader knows what is required in order to claim conformance and what is optional. To achieve this objective, throughout the document, employ uniformity of structure and style, and consistency of terminology and phraseology.
To fulfill this checkpoint, a specification MUST use RFC 2119 keywords to denote whether or not requirements are mandatory, optional, or suggested.
Rationale: Using these keywords helps to identify the testable statements in a specification.
Examples & Techniques for this checkpoint.
Normative statements are the prescriptive parts of the specification whereas informative statements are for informational purposes and assist in the understanding or use of the specification.
To fulfill this checkpoint, a specification MUST distinguish normative text from informative text.
Rationale: it is important that the reader be able to distinguish between normative and informative statements in order to know what is required to claim conformance. SMIL 2.0 is an example, indicating within every subsection whether it is normative or informative, and even separately labelling pieces of subsections that contain both kinds of text.
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST use identical wording to express identical provisions, and analogous wording to express analogous provisions .
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide at least one navigation mechanism that allows the reader to locate all conformance-related information that is relevant to the specification. The mechanism MUST minimally locate:
Rationale: A reader must be able to easily identify and locate all the information necessary to understand the conformance policy and related conformance information without having to read the document from cover to cover. A navigation mechanism adds to the usability of the specification.
A table of contents entry is one way to accomplish this. In addition to the minimal required set above, other conformance related information such as the ICS, location of test suites, etc, may be helpful to users and implementers.
Examples & Techniques for this checkpoint.
A test assertion is a statement of behavior, action or condition that can be measured or tested. It is derived from the specification's requirements and bridges the gap between the narrative of the specification and the test cases. Each test assertion is an independent, complete, testable statement for requirements in the specification. Each test assertion results in one or more test cases. Multiple test assertions can be combined to form a test case, in this case one tests multiple facets of a particular behavior.
To fulfill this checkpoint, a specification MUST include or reference normatively a list of test assertions stated in it.
In order to enable pointing to test assertions from tests as well as to give a map of the specification from the point of view of tests, use a mechanism for making explicit test assertions in the specification.
Rationale: providing test assertions facilitates and promotes the development of test materials. Tests can point directly to the test assertion. Specific benefits include:
Examples & Techniques for this checkpoint.
To fulfill this checkpoint, a specification MUST provide a mechanism linking each test assertion to the part of the specification it is stated.
Rationale: this allows both to ensure consistency between the specification and the test assertions list and to facilitate building a test suite framework based on the test assertions list.
Examples & Techniques for this checkpoint.
This section defines conformance of Working Group specifications — i.e., technical reports — to the requirements of this QA Framework guidelines specification. The requirements of this guidelines specification are detailed in the checkpoints of the preceding "Guidelines" chapter, and apply to the technical reports produced by Working Groups.
The test assertions of this Specification Guidelines document are found in the prioritized checkpoints. A checkpoint will contain at least one, and may contain multiple individual requirements. These requirements are the test assertions of this specification. A checkpoint is satisfied by satisfying all of the individual requirements. Failing one individual mandatory requirement means that the checkpoint is not satisfied. Mandatory requirements are those that use the conformance keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", or "SHALL NOT".
This section defines three degrees of conformance to this guidelines specification:
A specification conforms to the QA Framework: Specification Guidelines at degree X (A, AA, or AAA) if the Working Group meets at least all degree X conformance requirements.
To make an assertion about conformance to this document, specify:
Example:
This specification conforms to W3C's QA Framework: Specification Guidelines, available at http://www.w3.org/TR/qaframe-spec/, AA-Conforming.
The checkpoints of this guidelines specification present verifiable conformance requirements about the specifications (technical reports) that Working Groups produce. As with any verifiable test requirements, it is also true of these specification requirements that:
[] This section contains terms used in this specification, with functional or contextual definitions appropriate for this specification. See also [QA-GLOSSARY]. Some terms in this section have been borrowed or adapted from other specifications.
The following QA Working Group and Interest Group participants have contributed significantly to the content of this document:
While keeping most of the principles behind the second published WD, this version has re-ordered the guidelines in a more logical way, and takes a more formal approach in the design of CP, where all CP has a set of test assertions. Besides, repetitions have been diminished through factorization, and non-testable or arguable CP have been removed or marked as to be moved as examples and techniques. Finally, it integrates all the issues resolutions agreed during the QA WG Tokyo face-to-face meeting and the weeks following.
Ensure that every test assertion is covered by an example), 2.3 (
For each class of product, indicate minimal support requirements.), 3.1 (
Choose whether or not to have profiles.), 3.2 (
Include a table of contents entry.), 4.1 (
Choose whether or not to have modules.), 4.2 (
Include a table of contents entry.), 6.5 (
Include a table of contents entry.), 7.1 (
Address whether the specification uses or will use functional levels.), 7.2 (
Include a table of contents entry.), 9.7 (
Include a table of contents entry.), 10.3 (
Include a conformance clause entry in the table of contents), 10.5 (
Identify all dimensions of variability that are not used.) 11.5 (
Include a table of contents entry.), 13.3 (
Follow Web Accessibility Initiative and Internationalization Guidelines.)
Provide a fast way to find conformance information) is new
Significantly reorganized and revised the first published WD. This version produced as a series of editor's drafts. The changes below are reverse chronological (most recent first), so more recent ones may build on older ones.
First published WD.