Guo AH, Baliira R, Skinner ME, Kumar S, Andren A, Zhang L, Goldsmith RS, Michan S, Davis NJ, Maccani MW, Day SM, Sinclair DA, Brody MJ, Lyssiotis CA, Stein AB, Lombard DB. Sci Rep. 2022 Jul 18;12(1):12258. doi: 10.1038/s41598-022-16506-7. PMID: 35851833 Free PMC article.
Tom Rob Smith Epub 21
A ZIP-based archive with the file extension .epub bundles the EPUB publication'sresources for distribution. As conformant ZIP archives, EPUB publications can be unzipped by manysoftware programs, simplifying both their production and consumption.
While conceptually simple, an EPUB publication is more than just a collection of HTML pages anddependent assets in a ZIP package as presented here. Additional information about the primaryfeatures and functionality that EPUB publications provide to enhance the reading experience isavailable from the referenced specifications, and a more general introduction to the features ofEPUB 3 is provided in the non-normative [epub-overview-33].
Refer to [epub-rs-33] for the processing requirements for reading systems. Although it is notnecessary that EPUB creators read that document to create EPUB publications, an understanding ofhow reading systems present the content can help craft publications for optimal presentation tousers.
Inclusion as a core media type resource does not mean that all reading systems will support therendering of a resource. Reading system support also depends on the capabilities of theapplication (e.g., a reading system with a viewport must support image core media typeresources, but a reading system without a viewport does not). Refer to Core media types [epub-rs-33] for moreinformation about which reading systems rendering capabilities require support for which coremedia type resources.
A consequence of embedding is that the data in a data URL is not considered its own uniquepublication resource for manifest reporting purposes (i.e., only its containing publicationresource gets listed). As this data has its own media type, however, it is still subject to foreign resource restrictions. EPUB creators MUST thereforeencode data URLs as core media type resources or provide a fallback using the intrinsic fallbackmechanisms of the host format.
For example, URLs like :12345/ or :12345/ honor these properties. But URLs like :12345/path/to.epub/,file:///path/to.epub#path=/, or jar:file:/path/to.epub!/EPUB/do not (parsing the URL string ".." with these three examples as base wouldreturn :12345/path/, file:///path/, and a parsingerror, respectively). It is the responsibility of the reading system to assign a URL to theroot directory that complies with the properties defined above.
Although the EPUB container provides the ability to reference more than onepackage document, this specification does not define how to interpret, or selectfrom, the available options. Refer to [epub-multi-rend-11] for moreinformation on how to bundle more than one rendering of the content.
EPUB creators should use unprefixed properties and reading systems should supportcurrent CSS specifications. This specification retains the widely used prefixedproperties from [epubcontentdocs-301] but removes support for the less-used ones. EPUBcreators should use CSS-native solutions for the removed properties wheneveravailable.
EPUB creators should note that supportfor container-constrained scripting in reading systems is only recommended inreflowable documents [epub-rs-33]. Furthermore, reading system support infixed-layout documents is optional.
EPUB creators should note that support for spine-level scripting in reading systems is only recommended in fixed-layout documentsand reflowable documents set toscroll [epub-rs-33]. Furthermore, reading system support in all other contextsis optional.
The epub:type attribute is REQUIRED on a element descendants of thelandmarks nav element. The structural semantics of each link target within thelandmarks nav element is determined by the value of this attribute.
EPUB navigation documents MAY contain one or more nav elements in addition tothe toc, page-list, and landmarks nav elements defined inthe preceding sections. If these nav elements are intended for reading systemprocessing, they MUST have an epub:type attribute and are subject to the content modelrestrictions defined in 7.3 The nav element: restrictions.
EPUB publications, unlike print books or PDF files, are designed to change. The contentflows, or reflows, to fit the screen and to fit the needs of the user. As noted in Rendering and CSS "content presentationadapts to the user, rather than the user having to adapt to a particular presentation ofcontent." [epub-overview-33]
The seq element MUST contain an epub:textref attribute. As seq elements do notprovide synchronization instructions, this attribute allows a reading system to matchthe fragment to a location in the text.
Both the epub:textref attribute and the text element's srcattribute may contain a URL-fragment string that references a specific part (e.g., anelement via its ID) of the associated EPUB content document.
The granularity level of the media overlay depends on how EPUB creators mark up theEPUB content document and the type of fragment identifier they use in the textelements' src attributes and the seq elements' epub:textrefattrbutes. For example, when referencing [html] elements, if the finest level of markup isat the paragraph level, then that is the finest possible level for media overlaysynchronization. Likewise, if sub-paragraph markup is available, such as [html] spanelement representing phrases or sentences, then finer granularity is possible in the mediaoverlay. Finer granularity gives users more precise results for synchronized playback whennavigating by word or phrase and when searching the text but increases the file size of themedia overlay documents. Fragment identifier schemes that do not rely on the presence ofelements could provide even finer granularity, where supported.
The epub:type attribute facilitates reading system behavior appropriate for thesemantic type(s) indicated. Examples of these behaviors are skippability and escapability and table reading mode [epub-rs-33].
While reading, users may want to turn on or off certain features of the content, such asfootnotes, page numbers, or other types of secondary content. This feature is calledskippability. Reading systems use the semantic information provided by media overlayelements' epub:type attribute todetermine when to offer users the option of skippable features.
As the EPUB navigation document is an XHTML content document, EPUB creators may associatea media overlay document with it. Unlike traditional XHTML content documents, however, reading systems must present the EPUB navigation document to users even when it is not included in thespine (see Navigation document processing[epub-rs-33]). As a result, the method in which an associated media overlay behaves can changedepending on the context:
As the current WCAG guidelines (version 2) are heavily focused on web pages, a separate specification, EPUB Accessibility [epub-a11y-11], defines how to apply the standardto EPUB publications. It also adds EPUB-specific requirements and recommendations for metadata,pagination, and media overlays.
This specification recommends that EPUB publications conform to the accessibilityrequirements defined in [epub-a11y-11]. A benefit of following this recommendation isthat it helps to ensure that EPUB publications meet the accessibility requirements legislated injurisdictions around the world.
The effectiveness of these attacks also often depends on tricking users into believing that thepublication they are interacting with is from a trustworthy source. These deceptions can take thefollowing forms:
The one potential exception is the epubReadingSystem object [epub-rs-33] that allows EPUB creatorsto query information about the current reading system. EPUB creators need to be mindful thatthey only use the information exposed by this object to improve the rendering of their content(i.e., avoid using the information to profile the user and their environment).
When collecting and storing user information within an EPUB publication (e.g., through the use of cookies and webstorage [html]), EPUB creators need to consider to potential for data theft by other EPUBpublications on a reading system. Although [epub-rs-33] introduces a unique origin requirement for EPUB publications,which limits the potential for attacks, there is still a risk that reading systems will allow EPUBpublications access to shared persistent storage (e.g., older reading systems that have not beenupdated and non-conforming newer reading systems). Consequently, EPUB creators SHOULD NOT storesensitive user data in persistent storage. If EPUB creators must store sensitive data, they SHOULDencrypt the data to prevent trivial access to it in the case of an exploit.
Structural semantics add additional meaning about the specific structural purpose an element plays.The epub:type attribute is used to express domain-specific semantics in EPUB content documents and media overlay documents, with the structural information it carriescomplementing the underlying vocabulary.
This specification defines a method for adding structural semantics using the attributeaxis: instead of adding new elements, EPUB creators can append the epub:typeattribute to existing elements to add the desired semantics.
Although the epub:type attribute is similar in nature to the roleattribute [html], the attributes serve different purposes. The values of theepub:type attribute do not enhance access through assistive technologies likescreen readers as they do not map to the accessibility APIs used by these technologies. Thismeans that adding epub:type values to semantically neutral elements like [html]div and span does not make them any more accessible to assistive technologies. Only ARIAroles influence how assistive technologies understand such elements.
The epub:type attribute is consequently only intended for publishing semantics andreading system enhancements. Reading systems may use epub:type values toprovide accessibility enhancements like built-in read aloud or media overlays functionalitywhere interaction with assistive technologies is not essential. 2ff7e9595c
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