Description
Unlike Link and ULink, the semantics of OLink are application-specific. OLink provides a mechanism for establishing links across documents, where ID/IDREF linking is not possible and ULink is inappropriate.
In general terms, the strategy employed by OLink is to point to the target document via an external general entity, and point into that document in some application-specific way.
Processing expectations
Formatted inline.
OLink points to its target primarily with the TargetDocEnt attribute. TargetDocEnt must be the name of an entity (previously declared in the DTD or in the document subset).
Because TargetDocEnt is an entity attribute, the entity used as its value must be declared with a notation. Because the target is usually another SGML or XML document, the notation SGML is most often used:
<!ENTITY myotherdoc SYSTEM "myotherdoc.sgm" NDATA SGML>
The semantics of the link are controlled by three other attributes: LinkMode, LocalInfo, and Type. The LinkMode attribute points to a ModeSpec. The content of ModeSpec describes the semantic of the link in an entirely application-specific way.
The values of LocalInfo and Type may also influence the application. For example, if the ModeSpec describes some sort of query, LocalInfo might hold the query text (allowing multiple OLinks to use the same ModeSpec to achieve different queries with the same query engine).
Linking elements must not be nested within other linking elements (including themselves). Because DocBook is harmonizing towards XML, this restriction cannot easily be enforced by the DTD. The processing of nested linking elements is undefined.
Future Changes
The InterfaceDefinition element will be discarded in DocBook V4.0. It will no longer be available in the content model of this element.
Parents
These elements contain OLink: Abbrev, Ackno, Acronym, Action, Application, ArtPageNums, Attribution, AuthorInitials, BiblioMisc, BridgeHead, Citation, CiteTitle, City, CollabName, Command, Comment, ComputerOutput, ConfDates, ConfNum, ConfSponsor, ConfTitle, ContractNum, ContractSponsor, Contrib, CorpAuthor, CorpName, Country, Database, Date, Edition, Email, Emphasis, entry, Fax, Figure, Filename, FirstName, FirstTerm, ForeignPhrase, FuncParams, FuncSynopsisInfo, Function, GlossSee, GlossSeeAlso, GlossTerm, Hardware, Holder, Honorific, IndexDiv, InformalFigure, Interface, InterfaceDefinition, InvPartNumber, ISBN, ISSN, IssueNum, JobTitle, KeyCap, Label, Lineage, LineAnnotation, Link, Literal, LiteralLayout, LoTentry, ManVolNum, Member, ModeSpec, MsgAud, OLink, Option, Optional, OrgDiv, OrgName, OtherAddr, OtherName, PageNums, Para, Parameter, Phone, Phrase, POB, Postcode, Primary, PrimaryIE, ProductName, ProductNumber, ProgramListing, Property, PubDate, PublisherName, PubsNumber, Quote, RefEntry, RefEntryTitle, RefMiscInfo, RefNameDiv, RefPurpose, ReleaseInfo, Replaceable, RevNumber, RevRemark, Screen, ScreenInfo, Secondary, SecondaryIE, See, SeeAlso, SeeAlsoIE, SeeIE, Seg, SegTitle, SeriesVolNums, ShortAffil, SimPara, State, Street, Subscript, Subtitle, Superscript, Surname, Synopsis, SystemItem, Term, Tertiary, TertiaryIE, Title, TitleAbbrev, ToCback, ToCentry, ToCfront, Trademark, ULink, UserInput, VolumeNum, WordAsWord, Year.
Children
The following elements occur in OLink: Abbrev, Acronym, Action, Anchor, Application, Author, AuthorInitials, Citation, CiteRefEntry, CiteTitle, ClassName, CmdSynopsis, Command, Comment, ComputerOutput, Constant, CorpAuthor, Database, Email, Emphasis, EnVar, ErrorCode, ErrorName, ErrorType, Filename, FirstTerm, Footnote, FootnoteRef, ForeignPhrase, FuncSynopsis, Function, GlossTerm, GUIButton, GUIIcon, GUILabel, GUIMenu, GUIMenuItem, GUISubmenu, Hardware, IndexTerm, InlineEquation, InlineGraphic, InlineMediaObject, Interface, InterfaceDefinition, KeyCap, KeyCode, KeyCombo, KeySym, Link, Literal, Markup, MediaLabel, MenuChoice, ModeSpec, MouseButton, MsgText, OLink, Option, Optional, OtherCredit, Parameter, Phrase, ProductName, ProductNumber, Prompt, Property, Quote, Replaceable, ReturnValue, RevHistory, SGMLTag, StructField, StructName, Subscript, Superscript, Symbol, Synopsis, SystemItem, Token, Trademark, Type, ULink, UserInput, VarName, WordAsWord, XRef.
In some contexts, the following elements are allowed anywhere: BeginPage, IndexTerm.
In some contexts, the following elements are excluded: Acronym, Footnote, IndexTerm.