The principal goal of this document is to help W3C Working Groups in writing clearer, more implementatable, 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 WG version is substantially identical to 20020515 publication version.
This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest version 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.
This version is the first public Working Draft, and supersedes all previous WG-only drafts. It is expected that updated WD versions of this document will be produced regularly, along with other members of the Framework documents family. Future progression of this document beyond Working Draft is possible, but has not yet been determined.
In this version, a complete set of guidelines and prioritized checkpoints for W3C specifications (technical reports) is presented and explained. At this time, the QAWG (QA Working Group) has addresses the contents of the document at a high level, agreeing to the concepts and principles as well the coverage of the guidelines. The QAWG has not, at this time, addressed and achieved consensus of the priority levels. A future version of this document will be accompanied by a "Specification Examples & Techniques" document, which will illustrate the guidelines and checkpoints with case studies, and explain how to satisfy the checkpoints.
Please send comments to firstname.lastname@example.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 wouldn't 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.
1.1 Motivation for this guidelines document
1.2 Navigating through this document
1.4 Major Themes
G 1. Support general document conformance conventions.
G 2. Provide a conformance clause.
G 3. Specify flavors of conformance.
G 4. Identify what needs to conform and how.
G 5. Divide specification in order to group requirements.
G 6. Specify how to make a conformance claims.
G 7. Define user scenarios.
G 8. Define discretionary behaviors.
G 9. Clarify the relation between deprecated features and conformance.
G 10. Allow extensions or NOT!
G 11. Publish an Implementation Conformance Statement proforma.
G 12. Use granular grammars to author the specification.
3.1 Motivation for this Guidelines Document
3.2 Conformance disclaimer
An appendix to this document [SPEC-CHECKLIST] presents all checkpoints in a tabular form, for convenient reference.
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 unbaised manner.
This document defines a common framework for specifying conformance requirements and definitions, and for representing the structure of the document as schemata, both of which facilitate the generation of test materials. The primary goal is to assist W3C Working Groups (WGs) by providing guidelines and verifiable checkpoints for writing clearer, more implementable, and better testable specifications (technical reports). Good specifications lead to better implementations and foster the development of conformance test suites and tools. Conforming implementations lead to interoperability.
This guideline was developed so that WGs can apply it in a common-sense and workable manner. This document identifies the conformance requirements and statements to be included or addressed in specifications as well as addressing the anatomy of the specification. Conformance requirements are the expressions that convey the criteria to be fulfilled in an implementation of a specification. The conformance requirements are stated in a conformance clause or statements within the specification. The anatomy of the specification pertains to the method for writing the specification using schemata. A specification represented by an XML grammar with sufficient granularity of the information conveyed facilitates the generation of test materials by providing the ability to point to, extract, query, manipulate and/or automatically generate test materials. Given the symbiotic connection between specification and test materials, this document also addresses the intermixed QA-activities of specification authoring and test material production and maintenance within the W3C process.
This document is part of a family of QA Framework documents designed to improve the quality of W3C specifications as well as their implementations by solidifying and extending current quality practices within the W3C. The QA Framework documents are:
The process for developing testable technical reports and specifications is affected by QA-activities beyond those that are explicitly provided in this document. Specifically, the QA Framework documents are interrelated and complement each other. For example, the anatomy of a specification is dependent on the type of test materials that will be built - hence the interrelationship between this document and the Test Guidelines. Links between applicable guidelines in this document to the other Framework documents will be given.
The guidelines are intended for all Working Groups as well as developers of conformance materials for W3C specifications. Not only are the Working Groups the consumer 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.
The ultimate goal of a specification is to be implemented. In order to be implemented, a specification needs to be written such that developers and users can comprehend what is expected of them and build correct, robust, interoperable software and content. Correct utilization of specifications leads to portability and interoperability. In particular, it is easier to implement clear specifications, where the possibility of misinterpretation has been eliminated, safeguarding the quality of implementations. In addition, if care is given to the specifications, interpretability between W3C technologies is easier to track and assert.
Given that the W3C invests time and resources into producing specifications that are eventually implemented, and especially given that some of those specifications are interrelated, it makes sense to enhance and streamline the specification authoring process. This should be done for three main reasons:
The W3C needs to ensure that the deliverables of its WGs are clear, implementable and sound technical specifications with testable requirements and that can be used to easily generate Quality Assurance materials (tests and suites). A specification is testable if there exists some finite cost-effective process with which a person or software can check that the requirement has been met.
The benefits of producting clear, testable specifications include:
The benefits derived by writing granular specifications that provide detailed control over the information in the specification, include
In particular, information from the specifications is easier to extract if specification authoring involves a standardized set of specification schemas where both technology and intended behaviour is specified. Tests can be generated directly from the specifications, where needed, to generate primers for test suites. In this way, a fairly broad coverage of test cases can be achieved in a straightforward way. An added bonus is that a graphical representation of the specification can be generated in parallel to the normative HTML version. Specification granularity allows for more concise reporting when running test suites by pointing directly to the relevant part of the specification. Specification granularity allows for generating tests that can be validated against the specification itself, thus making it easier in those cases where different interpretations of the normative text are given.
Use of a formal (or formal-like) specification language may enable 'validate' specification as well as auto generation of tests or test components.
Synchronizing writing specifications with building test materials provides a feedback loop. Testing can help find ambiguities, inconsistencies, and holes in a specification.
Interaction between WGs and other bodies in specification authoring is related to test suite production and maintenance. The reasons to develop specifications and test assertions/test materials together are:
Since this document is part of a family of documents, the reader is strongly encouraged to be familiar with the other documents in the family. There is an interrelationship between the Guidelines in this document and the Guidelines in the other Framework documents. In particular, Guidelines 1, 2, 3 and 5 in the QA Framework: Operational Guidelines [QAF-OPS ] are especially relevant and interrelated to the Guidelines in this document.
This document describes what goes into the specification with respect to conformance and conformance topics, followed by the anatomy of the specification to enable test development as well as better, testable specifications. It does not preclude the need to apply the W3C Manual of Style [STYLE-MAN] and to conform to the Publication Rules [PUBRULES ] (member-only).
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 checkpoint definitions in each guideline define the processes and operations that need to be implemented in order to accomplish 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 separate appendix to this document [SPEC-CHECKLIST] presents all checkpoints in a tabular form, for convenient reference.
Many of the Guidelines are interwoven, especially Guidelines 2, 3, 4, and 5. We recommend reading these Guidelines and examples as a package rather than as individual, discrete Guidelines.
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].
Unusual terms in these framework documents are defined when first used, and most generally useful QA-specific terms will eventually be in the QA Glossary [QA-GLOSSARY].
The guidelines address two general themes: specifying conformance requirements in the specification, and addressing the anatomy of the specification.
Theme 1: Conformance content: general requirements and definitions concerning conformance and related issues. It is intended to contribute towards mutual understanding amongst developers of specifications and conformance test suites and tools. It does not define specific conformance requirements for any specific specification - this is the responsibility of the WG chartered to develop the specification. For the developers of specifications to help enable them to develop conformance requirements and to create testable, unambiguous specifications. A conformance clause:
Theme 2: Anatomy: invest in writing granular specification with careful modeling of the information conveyed. Allows for:
Guideline 1. Support general document conformance conventions.
There is a lot to be said about consistency and clarity within a document - it leads to the understanding and comprehensiveness of the document. Authors and editors of specifications should already be familiar with the W3C Manual of Style [STYLE-MAN] and Publication Rules [PUBRULES ], which help to achieve this. With respect to conformance, it is important to provide clear and ambiguous 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.
Checkpoint 1.1. Use conformance key words. [Priority 1]
Use RFC 2119 key words to denote whether or not requirements are mandatory, optional, or suggested. Using these keywords helps to identify the testable statements in a specification.
Checkpoint 1.2. Distinguish normative and informative text. [Priority 2]
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. 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 and what is optional.
Checkpoint 1.3. Follow Web Accessibility Initiative and Internationalization Guidelines. [Priority 1]
Applying the principles of the Web Content Accessibility Guidelines 1.0 [WCAG10] and Internationalization Guidelines (@@reference? what do you mean to point to here?) not only ensures accessibility and internationalization, but also contributes to the principles of conformance - clear, ambiguous, testable statements. For example, use simpler words to express your ideas, markup text with structural elements, add markup to distinguish common words from keywords.
Checkpoint 1.4. Use the same words to express the same ideas. [Priority 1]
Use identical wording to express identical provisions and analogous wording to express analogous provisions.
Guideline 2. Provide a conformance clause.
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.
Checkpoint 2.1. Include a conformance clause. [Priority 1]
Checkpoint 2.2. Create a separate conformance section. [Priority 2]
Having the conformance clause exist as a separate section within the specification makes it is clearly identifiable, allowing a reader to find all conformance provisions from a single starting point.
Checkpoint 2.3. Generate a conformance clause entry in the table of contents. [Priority 2]
Make normative reference to specifications on which the current specification depends.
Often a specification is dependent on other specifications or portions of specifications. For example requiring that the class of product called "user agent" be consistent with the XML 1.0 Recommendation [XML10 ] and support Cascading Style Sheets, level 1 [CSS1]. The inclusion or reference to related specifications can affect conformance of the current specification. To ensure clarity and understanding of these implications, provide a description of the relationship between the specifications and any conformance implications. Linking from the prose to the reference is described in the linking parts of the Manual of Style ([STYLE-MAN], section 11.5.1).
Guideline 3. Specify flavors of conformance.
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 if there are various flavors, what is meant by each flavor. Examples of flavors include: unconditional conformance, conditional conformance, and strict conformance. Strict conformance is defined as conformance of an implementation that employs only the requirements of the specification and no more (e.g. no extensions). For a definition and example of conditional conformance, see the conformance clause of User Agent Accessibility Guidelines (UAAG) 1.0, ([UAAG10], section 3.2)
Checkpoint 3.1. Choose one or more of the following flavors: (a) strict conformance, (b) conditional and unconditional conformance, (c) other, (d) no flavor. [Priority 2]
Choice (a) and (b) are flavors that have been used within W3C Technical Reports. Choice (c) provides you the ability to specify your own flavor. If choice (d) is selected, it should be made clear to the reader that the specification does not contain flavors of conformance. It is often necessary to define these flavors within the context of the specification, noting how they apply and possibly providing examples. Note that it is possible for a specification to use more than one flavor if the flavors are assigned to specific classes of products or modules or profiles. Care should be exercised in choosing more than one flavor, to avoid confusion.
Checkpoint 3.2. If (a) or (b) or (c) is selected, generate a table of contents entry. [Priority 2]
The reader should be able to easily identify and locate this information. A link from the table of contents provides this ability.
Checkpoint 3.3. For choice (a), include a definition of strict conformance in the specification. [Priority 2]
Either use the definition provided above (or in the QA Glossary [QA-GLOSSARY]), modify it, or provide your own definition. It is strongly recommended that the definition given above be used to ensure consistency across WGs and promote a common understanding of conformance requirements.
Checkpoint 3.4. For choice (b), include a definition of conditional and unconditional conformance in the specification. [Priority 2]
In general, unconditional conformance means that all the requirements are satisfied (i.e., the default set). Conditional conformance means conformance to less than (or more than) a default set of requirements. It is necessary in defining these terms to specify the conditions or terms that govern their application. The UAAG 1.0 [UAAG10] uses these terms, providing their definition as well as how they are applied to implementations of the specification.
Checkpoint 3.5. For choice (c), provide the name of the flavor and its definition within the specification. [Priority 2]
Guideline 4. Identify what needs to conform and how.
Catagorizing 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 help answer this question, it helps to look at the nature of the specification and catagorize it. Most specifications can be classified into one of the following six catagories:
One specification could potentially fall into more than one catagory.
From this catagorization of specifications, the WG can identify the 'class of products' that are affected by the specification. Classes of products can be generalized as either producers or consumers. Identifying which are producers and consumers is very 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 indentifying 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.
Checkpoint 4.1. Identify all classes of product. [Priority 1]
For example, within the SMIL 2.0 Language Profile ([SMIL20], chapter 13), there are 2 classes of products: documents and basic user agents and within Mathematical Markup Language (MathML) 2.0 [MATHML20] there are output-compliant, authoring tools and input-compliant, rendering/reading tools. For specifications that are used as components of other specifications and rely on these other specifications to define conformance, indicate that conformance criteria for independent implementations are not defined within the specification. For example, Xpath ( XML Path Language 1.0 , [XPATH10]) relies on specifications that use XPath -- such as XPointer ( XML Pointer Language , [XPOINTER]) and XSLT ( XSL Transformations 1.0 , [XSLT10]) -- to specify criteria for conformance of implementations of XPath.
Checkpoint 4.2. For each class of product, define the conformance requirements. [Priority 1]
The conformance requirements indicate the conditions to be satisfied in order to claim conformance. In addition to specifying the requirements for claiming conformance, it may be appropriate to specify that which is not a requirement. It is likely that these conformance definitions will reference normative text within the specification or in other related specifications.
Checkpoint 4.3. Indicate minimal support requirements. [Priority 3]
Describe the minimum set of elements, attributes, etc., that are required to claim conformance for a specific module and/or class of product. This information is often presented in tabular form (e.g., SMIL 2.0 section 2.4, table 5). If applicable, indicate that there are no minimum support requirements. This is helpful in providing the reader a full understanding of the conformance requirements, especially when some of the classes of products have minimal requirements whereas others do not.
Guideline 5. Divide specification in order to group requirements.
Dividing a specification into functional groupings can facilitate its implementation by enabling a developer to build to portions of the specification rather than implementing the entire specification. These groupings of functional requirements may be non-hierarchical as in the case of modules and profiles or hierarchical divisions as in the case of levels. Note that particular profiles may be hierarchical, but hierarchy is not a necessary characteristic of profiles as it is for levels. Modules are discrete divisions of the specification and can be implemented independently (e.g., audio vs. video module). It is possible and common to implement multiple modules. The union of all the modules does not necessarily equal the constitute the entire specification. Proifles are a subset of the specification that supports a functional objective. Profiles can also be used to group a set of standards or modules and define how they are required to operate together. The union of all the profiles does not necessarily constitute the entire specification. Levels are used to group functionality into nested subsets, ranging from minimal or core functionality to full or complete functionally. Typically, Level 1 is the minimal or core of the specification. Level 2 includes all of level 1 and also additional functionality. This nesting continues until level n, which consists of the entire specification.
To illustrate using the SMIL Recommendations (e.g., [SMIL20]) - Modularization is an approach in which markup functionality is specified as a set of modules that contain semantically-related XML elements, attributes and attribute values. Profiling is a method for defining subsets of a specification by identifying the functionality, parameters, options, and/or implementation requirements necessary to satisfy the requirements of a particular community of users. In SMIL, it is the creation of an XML-based language through combining these modules, in order to provide the functionality required by a particular application. SMIL 2.0 defines all modules, levels and profiles -- three modules (timing, ...), levels (regular, extended animation), and profiles are defined at the end of the specification.
Exercise caution - experience has shown that having too many modules/profiles/levels can inhibit interoperability as well as add to confusion in the marketplace.
Checkpoint 5.1. Choose one or more of the following methods for grouping or dividing up the specification: a) modularization, b) profiling, c) levels, d) none of the above. [Priority 1]
It is possible for a specification to have modules, profiles, and levels. If choice (d) is selected, it should be clear to the reader that the specification does not contain modules, or profiles. One way to ensure this clarity is to explicitly state that none of these are supported.
Checkpoint 5.2. If (a), (b), and/or (c) was selected, ensure that a table of contents entry is generated. [Priority 1]
The reader should be able to easily identify and locate this information. A link from the table of contents provides this ability.
Checkpoint 5.3. For (a), (b) and/or (c), indicate whether its use is mandatory. [Priority 1]
If there are additional conditions associated with a particular module/profile/level, they should also be described. For example: any restrictions or constraints on the number or types of modules that can be implemented, if one and only one module/profile/level can be implemented at a time, or if specific modules can not be used in combination.
Checkpoint 5.4. For (a), (b) and/or (c), define any minimal requirements. [Priority 2]
Checkpoint 5.5. For (a), (b), and/or (c), indicate relationships between modules, profiles, and/or levels. [Priority 2]
Often there is a kind of layered dependency or interrelationship among modules, profiles and/or levels. Consider whether or not a claim of conformance to a particular module/profile/level can include functionality or features of another module/profile/level. For example, can implementations that purport to conform to a specific module include functionality defined in another module?
Guideline 6. Specify how to make a conformance claims.
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 confomrance.
Checkpoint 6.1. Identify and define all conformance levels or designations. [Priority 1]
The naming convention used to label the conformance can provide useful information, such as imply incremental importance or difficulty. Functional specifications use functionality to differentiate between conformance levels - the lowest level of conformance is defined by a core set or minimally supported features, the next level of conformance would include the core plus additionally features, etc. until the entire specification was covered. For example, the modularization description of SVG 1.1 (Scalable Vector Graphics 1.1, [SVG11], section 1.1.2) identifies three conformance levels (i.e., basic, tiny, and full) where each level subsumes the lower level, providing additional functionality and/or complexity. In contrast, the WAI Guidelines specifications (e.g., Web Content Accessibility Guidelines 1.0 [WCAG10]) and the QA Framework Guidelines specifications (e.g., this document) use a 3-level conformance format (A, AA, AAA) to convey priorities based on a checkpoints impact.
Checkpoint 6.2. Provide specific wording of the claim. [Priority 3]
A well-formed conformance claim includes: date of the claim, specification name, date and version, URI of the specification, conformance level satisfied, and information about the subject (that which is claiming conformance). Information about the subject refers to information such as, the name of the software or software component, version information, and operating environment.
Checkpoint 6.3. Provide a conformance disclaimer. [Priority 3]
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 guaruntee that the claimant is 100% conforming with the specification. A disclaimer can help clarify the meansing of a conformance claim as well as its limitations. For example, this document contains a conformance disclaimer.
Checkpoint 6.4. Impose no restrictions about who can make a claim or where claims can be published. [Priority 1]
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. As of the publication of this document, W3C does not act as an assuring party, but it may do so in the future, or it may establish recommendations for assuring parties. Claimants are expected to modify or retract a claim if it may be demonstrated that the claim is not valid.
Checkpoint 6.5. Generate a table of content entry. [Priority 2]
The reader should be able to easily identify and locate this information. A link from the table of contents provides this ability.
Guideline 7. Define user scenarios.
When writing specifications it is critical to understand their primary purpose and scope. If the specification describes a protocol or Application Programmer Interface (API) -- examples XML Protocol, DOM-- there should be a clear understanding of the primary user scenarios. If the specification describes content requirements (for example, [WCAG10], [UAAG10]), understanding of their purpose is they key to define the minimal sufficient set. Clearly defined scope helps to keep the specification content focused and unambiguous. When reading the specification, we face similar difficulties. To understand what the document says, the reader needs to know the context of the author, what were the scenarios the author had in mind. In case of protocols and APIs specifications developers try to assess whether the specifications covers the user scenarios the product needs to cover. Having no user scenarios described in the specification generates misuses of the spec itself.
Checkpoint 7.1. Define the scope of the specification. [Priority 1]
This is very basic but powerful requirement. The specification must clearly define what scenarios are in scope and what are out of scope in order to be interpreted, implemented, and tested correctly.
Checkpoint 7.2. Include Use Cases. [Priority 2]
A Use Case is a description of the user scenario given in formally defined terms. Once included in the specification Use Cases become Normative, unless otherwise specified. The specification should have extensive list of the orthogonal Use Cases the authors have in mind. Priorities MAY be assigned to the Use Cases, describing how important the particular scenario is for the specification. Use Cases in their turn may help to assess what features are missing and what features are superfluous in the specification.
Checkpoint 7.3. Include examples. [Priority 1]
It is good practice to illustrate each behavior or requirement in the specification by short and precise examples.
Checkpoint 7.4. Include an interpretation section. [Priority 2]
It is hard to understand the formal descriptions content without the informative interpretation. The recent complex specifications like XML Schema [XML-SCHEMA] and XML Protocol have shown an absolute necessity to have a "Primer" part or section to illustrate how to use the specification. Such a section does not substitute for the numerous examples needed for each requirement or behavior described in the specification, but illustrates how the specification fulfills the User Scenarios.
Guideline 8. Define discretionary behaviors.
Discretionary choices are often made available in specifications, giving vendors of technology the opportunities to decide from alternatives when implementating applications and tools. Discretionary behavior is when a specification deliberately and explicity grants discretion to the implementation - that is, describe or allows optionality of behavior, functionality, parameter values, error handling, etc. Discretionary items may be warranted 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 may be enumerated choices, wehere the implementation must choose from a set of prescribed choices or it may be describe open-ended discretion, such as locales.
One type of discretionary item is implementation dependent values. Implementation dependent values are used when it is not possible to define the behavior or values of a function. Implementation dependent means that an implementation may determine the effect, rather than having the effect mandated by the specification. Details in a specification may deliberately be omitted (i.e., not specified), so as to provide freedom to adapt implementations to different environments and different requirements. In general this is not a recommended practice.
Checkpoint 8.1. Explicitly state the cases and conditions where discretion is allowed and/or expected. [Priority 2]
Although there may be many individual discretionary choices sprinkled throughout the specification, they often arise from broader ideas about how the specified software should operate. To assist readers, implementers and testers find these discretionary items, it is recommended that where ever possible these items be collected and presented as a group. For example, in XSLT [XSLT10] most discretionary items offer two choices, representing design philosophies to escalate an error or to continue processing. Thus, XSLT could address discretion as a choice between two groups of items.
Checkpoint 8.2. Indicate implementation dependencies and where applicable address allowable differences between implementations. [Priority 1]
Examples of allowable differences to be addressed include:
Checkpoint 8.3. Describe alternative approaches and the conditions under which an implementation is considered to be conforming. [Priority 1]
Specifications may describe several different ways to accomplish its operation (e.g., a choice of file formats, protocols, or encodings). In such a case, enumerate the approaches and specify if there are limitations on the number of approaches or combination of approaches that can be implemented. Some possible ways to define conformance when allowing alternative approaches include mandating that an implementation:
Note that if the specification does not include the different approaches, this becomes an implementation detail.
Checkpoint 8.4. Include a statement regarding consistent handling of a discretionary item within an implementation. [Priority 2]
The effect of a discretionary item should be consistent within a single implementation. For example, a browser's rendering of a XSL-FO (XSL Formatting Object) should be the same for every invocation regardless of the document instance.
Checkpoint 8.5. Generate a table of contents entry. [Priority 2]
Guideline 9. Clarify the relation between deprecated features and conformance.
After the initial publication of a specification, specification developers may consider the deprecation of a feature (i.e., element or attribute) defined in the specification. A deprecated feature is a feature whose use is discouraged because it has been outdated by newer constructs or is no longer viable. 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 affect 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 would not use the feature, but user agents would continue to support it.
Checkpoint 9.1. Identify and clearly indicate each deprecated feature. [Priority 1]
Checkpoint 9.2. For each class of product, specify the level of support required for each deprecated feature and the conformance consequences of the deprecation. [Priority 1]
Define what it means for a feature to be deprecated and how this affects conformance. For example, a deprecated-features section of MathML 2.0 ([MATHML20], section 188.8.131.52) 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.
Checkpoint 9.3. Include an explanation for the deprecation. [Priority 3]
Providing the rationale for deprecating a feature is 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.
Checkpoint 9.4. Include examples to illustrate how to avoid using deprecated features. [Priority 3]
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 implementors to discontinue use of the deprecated feature.
Checkpoint 9.5. Generate a table of contents entry. [Priority 2]
Guideline 10. Allow extensions or NOT!
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. Care should be exercised 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 may be 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 are in demand 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 more likely to impede interoperability that a specification that requires extensions to be registered.
Checkpoint 10.1. If extensions are disallowed, explicitly state it. [Priority 3]
If extensions are not allowed, then make sure its clear to the reader that not only are extensions not allowed, but the circumstances under which that are not allowed. The implementations of the specification precisely implement the specification. 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.
Checkpoint 10.2. If extensions are allowed, explicitly state it. [Priority 1]
State the conditions under which extensions are allowed, the applicability of the extensions, their affect on conformance claims, and any limitations or restrictions on the use of the extension.
Checkpoint 10.3. If extensions are allowed, make it clear that the extensions do not negate support for required functionality. [Priority 1]
An extension does not change the fact that an implementation needs to support all required functionality in the specifications exactly as specified; nor does it cause the non-conformance of functionality defined in the specification. The specification can include statements such as:
Checkpoint 10.4. If extensions are allowed, use a standard mechanism to define the extension. [Priority 3]
One mechanism to allow extensions within a specification is to provide a standard way of defining the extension or a "standard way of being non-standard". 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). The nature of the extension dictates the method for defining the extension. It may be possible to define a generic function or mechanism that indicates external functionality. This external function may take the form of an escape or control character or be an identify, which whenever invoked indicates an extension follows. Another method, especially when extending a list of numeric parameters is to use a scheme where positive values represent standardized values and negative values are reserved for private extensions.
Checkpoint 10.5. If extensions are allowed, register or publish them. [Priority 3]
Registration is a procedure that allows extensions to be acknowledged and made available to the public. Registration provides for a degree of rigor and technical review for any proposed extension. Typically the WG would be responsible for processing the registration of an extension, thus ensuring adequate quality of a proposed extension and a technical description sufficient to be uniformly implementable. Often registered extensions may migrate into a later version of the specification.
Checkpoint 10.6. If extensions are allowed, require that implementations include a way to operate without the extension. [Priority 3]
If an implementation contains extensions, require it to have a mode under which the implementation can be directed to produce only conforming files (documents) or to operate in a strictly conforming manner.
Checkpoint 10.7. Generate a table of contents entry. [Priority 2]
Guideline 11. Publish an Implementation Conformance Statement proforma.
An Implementation Conformance Statement (ICS) or questionnaire is useful in clarifying and declaring 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 ICS is also helpful in describing the expected interoperabliity to be achieved with other implementations or applications of the specifications.
Checkpoint 11.1. Include an Implementation Conformance Statement proforma as part of the specification. [Priority 3]
If an ICS is included as part of the specification, indicate whether it is a normative or informative part of the specification.
Checkpoint 11.2. Require the ICS be completed as part of the conformance claim. [Priority 3]
An ICS provides specific information about the implementation and can be helpful in substantiating the conformance claim.
Guideline 12. Use granular grammars to author the specification.
Using a W3C endorsed grammar language (DTD or XML Schema) provides control over the information conveyed in the specification. This allows for and facilitates automatic generation of test materials, more detailed reporting of test results as well as specification coverage.
Examples include the XML and DOM Working Groups, that both use the xmlspec DTD .
Using a granular grammar to author a specification draws further on separation of content and presentation and simplifies the task of generating readable versions of the specification, maintaining the possibility to generate test materials from the granular version of the specification. In addition, using a grammar to author the specification makes it easier to logically group the constituents of the specification, thus adding control over interpretation and implementation.
Using a grammar greatly simplifies controlling conformance with W3C publication rules and guidelines/checkpoints. Also, having written the specification using a grammar, automated validation with regard to these aspects is simplified.
Using an advanced schema for specification authoring finally allows for greater control over coverage of the specification in the Test Suite.
Checkpoint 12.1. Use W3C endorsed grammar where applicable. [Priority 1]
One example is the DTD noted above. Other examples will be given.
Checkpoint 12.2. Specify intended behavior in the specification using markup. [Priority 1]
There are different types of technologies that are specified, and this checkpoint applies in different ways to those. For API specifications, such as DOM, the intended behavior is the algorithm output; the specification contains wording on what the expected result of applying a particular method on an interface is. On user-centric specifications, such as WAI guidelines specifications, the intended behavior is not so much a question of testing algorithms, but rather how user agents should behave given different input or how markup should be designed. In this case, intended behavior is more a question of parsing documents. On processor specifications, such as XML, the intended behavior is, for example, preserving or expanding entity references, and the intended behavior is a particular state after processing a document.
Checkpoint 12.3. Supply prose description of intended behavior together with each test assertion. [Priority 1]
Following the guideline below, group test assertions and statements of intended behavior in the specification, or group the pointer to the test assertions together with the statement of intended behavior in the specification (in case the test assertion is eg. given in an appendix).
Include test assertions.
Some specifications include test assertions as part of the specification, and more should. 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 behaviour. Including test assertions as part of the specification facilitates and promotes the development of test materials. Tests can point directly to the test assertion in the specification. Specific benefits include:
Checkpoint 12.4. Supply test assertions in the markup of the specification, if applicable using a set of predefined tags used in the specification markup language. [Priority 1]
Checkpoint 12.5. Tag test assertions according to the above. [Priority 1]
This section defines conformance of Working Group processes and operations to the requirements of this specification. The requirements of this specification are detailed in the checkpoints of the preceding "Guidelines" chapter of this specification, and apply to the Working Group QA-related documents and deliverables required by this specification.
This section defines three levels of conformance to this specification:
A specification conforms to the QA Framework: Specification Guidelines at Level X (A, AA, or AAA) if the Working Group meets at least all Conformance Level X requirements.
To make an assertion about conformance to this document, specify:
This specification conforms to W3C's QA Framework: Specification Guidelines, available at http://www.w3.org/TR/qaframe-spec/, Level AA.
The checkpoints of this 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:
The following QA Working Group and Interest Group participants have contributed significantly to the content of this document: