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It can be useful to specify all or part of a dimension in terms of components of another dimension. For some applications, this technique can be used to represent alignment and synchronization relationships. This sub-clause specifies HyTime's facilities for dimension references and the constraints imposed on them.
When the scheduling module is supported, the first marker of a dimension specification in an extent specification of an event, modscope, or proscope can be omitted. The omission of the first marker is an implicit reference to the previous specified event's, modscope's, or proscope's dimension. The omission of the first marker indicates that the "first" component of the dimension with the implicit dimension reference is the next MDU after the highest MDU occupied by the previous specified event, modscope, or proscope on the same axis of the same FCS.
NOTE 292 The effect of this rule is that the implicitly referencing event's first quantum will follow the previous specified event's last quantum on the given axis without a gap.
NOTE 293 This implicit representation of the start of an event allows an extent specification to be portable; that is, it can be referenced for use in other positions, which are determined by the dimension of the event preceding the event whose extent specification contains the reference.
The phrase "previous specified" normally refers to the element that was last parsed before the current element in the SGML representation of the document, in this case, the element of the same HyTime element form (e.g., event) previous to the current one.
NOTE 294 As some objects that occur in events have an inherent extent (for example, audio or video clips), it might seem logical to allow defaulting of the second marker to that value. However, such a rule would require a HyTime engine to understand every possible object notation in order to calculate the extent. Instead, HyTime requires the application that originated the document to specify the inherent extent in a standardized way, such as through a marker function.
The element form explicit dimension reference (dimref) references a component of a dimension (the "referenced dimension") associated with a specified element (the "element specified"). The element specified must be an extent, extlist, event, modscope, proscope, evgrp, modgrp, progrp, evsched, wand, baton or fcs. A set of extents is derived from the element specified, from which the referenced dimension is selected according to parameters supplied as the other attribute values of the dimref. The dimension may be a directly scheduled dimension (that is, directly specified for a given FCS via unprojected extent specifications), or an indirectly scheduled dimension (that is, indirectly specified for a given FCS as a result of projection onto that FCS).
While the syntactic mechanisms used to create dimension references refer to elements, the actual dimensions referenced are those of the events, modscopes and proscopes that occur in the grove constructed by a HyTime engine in the process of interpreting a HyTime document. The dimensions referenced are the dimensions derived from projected and/or unprojected events, modscopes and proscopes after all HyTime processing has been applied, all indirections have been resolved, and all projections have been completed.
Logical sets of events, modscopes, and proscopes that correspond to syntactic scheduling constructs, including fcs elements, evscheds, wands, batons, evgrps, modgrps, and progrps, do not have actual extents. However, for purposes of dimension referencing, such scheduling constructs are regarded as having implicit extents just large enough to contain all of a selected subset of the events, modscopes, and proscopes that they syntactically contain, logically schedule, or logically contain (depending on the selection parameters used in the dimref).
The interpretation and semantics of explicit dimension references are governed by the HyExSpec notation.
In this subclause, the term "directly scheduled" means "scheduled directly in the FCS, rather than being projected there." The term "projected" means just the opposite: "scheduled indirectly in an FCS by projection."
The dimref form is described first as it applies to the dimensions of directly scheduled events, modscopes, and proscopes, followed by a description of the additional attributes and constraints for referencing the dimensions of projected events, modscopes, and proscopes.
The attribute element specified (elemspec) refers to the element from which the dimension is to be derived. The specified element must be a client of one of the forms: extent, extlist, event, modscope, proscope, evgrp, modgrp, progrp, evsched, wand, baton, or fcs. It must refer to exactly one element.
NOTE 295 Dimrefs are not references to the syntactic axis markers
contained by or referenced from elements. Rather, they are references
to dimensions in FCSs resulting from the application of HyTime
processing. In order to reference such a resulting dimension, it is
necessary to know, at a minimum, the FCS, the axis of that FCS, the
extent(s) of the events, modscopes, and proscopes whose dimension(s)
are being referenced, and how to interpret those extents. Extents
resolve to axis markers, but the granules in which those axis markers
are expressed, and which dimensions map onto which axes, cannot be
learned from the extents themselves. It is also necessary to know the
order in which the markers for the axes are specified in the extents
and granules used for each axis. That information comes from the
axisord attribute of the governing evsched, wand, or baton. The element specified is not allowed to be a dimspec because it is
not necessarily sensible (a dimspec may appear in a variety of
contexts other than an extent of an event, modscope or proscope), it
would require more context to be provided (it might not otherwise be
clear which axis the dimspec is specified for), and because it is not
necessary, due to the fact that even more selectivity is already
provided by the extnum and dimnum parameters of the dimref form.
The attribute selected component of dimension (selcomp) selects the component of the referenced dimension that is to be used: first or lowest quantum (first), last or highest quantum (last), or quantum count (qcnt).
NOTE 296 The number of MDUs per reported quantum is derived from the value of the granule attribute.
The attribute flip selected component (flip) specifies whether the selected component is to be counted and signed in the usual way, or "flipped". If the value of the flip attribute is noflip, the "first" component is reported as a positive integer corresponding to the number of the first quantum counting from the beginning of the axis, the "last" component is reported as a negative integer corresponding to the number of the last quantum counting from the end of the axis, and the "qcnt" component is reported as a positive integer. If the value of the flip attribute is flip, "first" is reported as a negative integer corresponding to the number of first quantum counting from the end of the axis, "last" is reported as a positive integer corresponding to the number of the last quantum counting from the beginning of the axis, and "qcnt" is reported as a negative integer.
NOTE 297 Flip is useful when performing arithmetic on referenced dimensions.
The combinations of selcomp and flip can be summarized informally as
follows:
First quantum, counted from beginning (positive). Last quantum, counted from end (negative). Size; number of quanta (positive). First quantum, counted from end (negative). Last quantum, counted from beginning (positive). Negative of size (negative).
The attribute element with the sched attribute form specified (schdspec) specifies exactly one element that has the sched attribute form with values that guide the resolution of the desired referenced dimension. Specifically, the fcs attribute of the sched attribute form specifies the FCS in which the extents associated with the element specified by the elemspec attribute are scheduled, and the axisord attribute specifies both the axis order in which the dimension specifications of the extents are specified, and the granules used to specify the quantum numbers and quantum counts in the dimension specifications.
A value must be specified for the schdspec attribute if the element specified is an extent or extlist. A value may be specified if the element specified is an event, modscope, proscope, evgrp, modgrp, or progrp; in such a case, if no value is specified, the containing element with the sched attribute form is treated as if it were referenced by the value. The value of the schdspec attribute is ignored if the element specified is an evsched, wand, baton, or fcs. The element with the sched attribute form specified by the schdspec attribute must be one that governs the scheduling of the extents associated with the element specified by the elemspec attribute.
NOTE 298 Any given event, modscope, proscope, evgrp, modgrp, or progrp
element may appear in more than one evsched, wand, or baton element.
For example, an evsched may incorporate an event by means of a
HyTime valueref attribute. In such a case, if the referenced dimension
is governed by the incorporating evsched, the incorporating evsched
should be specified explicitly by the schdspec attribute. Extents and extlists are resources that can appear syntactically
outside the context of any element with the sched attribute form; this
is why, when the element specified is an extent or extlist, a value
must be specified for the schdspec attribute.
NOTE 299 In cases where the element specified is evsched, wand, or baton, the value of the schdspec attribute is ignored because these elements themselves use the sched attribute form. In cases where the element specified is an fcs, it is ignored because there is no need to interpret specific extent specifications in specific scheduling contexts.
The attribute axis specified (axisspec) specifies the axis on which the referenced dimension occurs. A value must be specified unless the schdspec attribute specifies or defaults to an evsched, baton, or wand whose sched attribute form specifies only one axis; if there is only one axis, the value of the axisspec attribute is ignored.
The attribute dimension number (dimnum) selects the referenced dimension from a set of dimensions.
NOTE 300 For example, if no value is specified for the extnum attribute, and there is more than one extent, dimnum can be used to select a single dimension.
The value of the dimnum attribute is the number of the corresponding dimension; a value of 1 (one) indicates the first dimension. The order of the dimensions is not determined by their lexical order of appearance in the document. Instead, the dimensions are sorted primarily by the number of the first quantum (counted starting with the first quantum on the axis), and secondarily by the qcnt, where lower quantum numbers come before higher ones, and smaller qcnts come before larger ones. The order of equivalent dimensions is undefined.
If there is more than one dimension and there is no dimnum specification, the referenced dimension is the smallest dimension that would encompass all the dimensions.
When the element specified is an event, modscope, or proscope that is scheduled with multiple extents, or when multiple extents are associated with the element specified by virtue of its containment of multiple events, modscopes, or proscopes, or both, the attribute extent number (extnum) specifies which syntactic extent to use in determining the referenced dimension. The extnum attribute is ignored if the element specified is an extent.
NOTE 301 By definition, an extent element defines only a single extent.
The use of notations (such as the HyExSpec notation) and marker functions makes it possible to describe lists of extents (extlists) in a single element whose content does not mark up each extent specification as an individual extent element. In such a case, the element is regarded as a single extent for purposes of extnum specifications.
NOTE 302 In such a case, the value of the dimnum attribute can be used to select individual dimensions, if desired.
An extnum value of 1 (one) indicates the first extent. The order of the extents is determined first by the syntactic order of the selected elements whose exspec attributes specify the extents, secondarily by the syntactic order of their specifications in the values of the relevant exspec attributes, and finally by the order of appearance of the extents in the source document (that is, within the specified extlists). If there is more than one extent and no value is specified for the extnum attribute (or if the selected extent has more than one dimension), and there is no dimnum specification, the referenced dimension is the smallest dimension that would encompass all the dimensions.
NOTE 303 Only events, modscopes and proscopes have exspec attributes. If, for example, the element specified by the elemspec attribute is an evsched containing two evgrps, and each evgrp contains three events, and each event has one extent, then there are six extents that can be selected using a value for the extnum attribute of 1, 2, 3, 4, 5, or 6. If no value is specified for the extnum attribute, all six extents are selected. (If no value is specified for the dimnum attribute, either, the referenced dimension is a fictitious one that is just big enough to contain all six.)
NOTE 304 Extnum selects from syntactic constructs in an order derived from the syntax of the document. Dimnum is entirely different; it selects from logical dimensions in the order in which they appear on the axes of fully processed logical FCSs.
When the element specified is an evsched, wand, baton, or fcs, the attribute directly scheduled types for calculating referenced dimension (dsdtypes) limits the types of constructs that will be taken into account when calculating the referenced dimension. The value of the dsdtypes attribute is a list of tokens, either keywords corresponding to the various scheduling forms or the GIs of client elements derived from scheduling forms.
The keyword #ALL causes all construct types to be taken into account. If #ALL is not specified, only the construct types that are specified in the value will be taken into account. All types of events, modscopes, proscopes, evgrps, modgrps, progrps, evscheds, wands, batons, and FCSs will be taken into account if the value contains keywords corresponding to those forms: #EVENT, #MODSCOP, #PROSCOP, #EVGRP, #MODGRP, #PROGRP, #EVSCHED, #WAND, #BATON, or #FCS. In addition, all elements whose GIs appear as tokens in the value of the dsdtypes attribute, and that are events, modscopes, proscopes, evgrps, modgrps, progrps, evscheds, wands, batons, or fcs elements, will be taken into account.
NOTE 305 It would be redundant to specify, for example, both #PROSCOP and the GI of a proscope element in the value of an dsdtypes attribute, although it is not an error to do so.
Any combination of the foregoing keywords and GIs may be used in the value of the dsdtypes attribute. If no value is specified, the default value will depend on the form of the element specified, according to the following table:
(null string)
"#EXTENT #EXTLIST"
"#EXTENT #EXTLIST #EVENT #EVGRP"
"#EXTENT #EXTLIST #MODSCOP #MODGRP"
"#EXTENT #EXTLIST #PROSCOP #PROGRP"
"#ALL"
The attribute granule for reporting (granule) names the granule to be regarded as the quantum used to report the referenced dimension. If no value is specified, the referenced dimension is reported in terms of the MDU in effect on the axis of the referenced dimension. The granule specified must be defined in terms of the same SMU as the axis specified by the axisspec attribute. If the granule is larger than the MDU of an axis, there may be less than one granule's worth of MDUs at the end of the axis after the last granule.
NOTE 306 In other words, the last granule's last MDU may not be the last MDU on the axis, with the number of remaining MDUs equal to the remainder after dividing the number of MDUs on the axis by the number of MDUs per granule.
The attribute round off to granule handling (roffgran) specifies how to handle a situation in which reporting the referenced dimension using the granule specified by the granule attribute would not be exactly accurate. The value round off error (roerr) indicates that if rounding is required, it is an error. The value round off to minimum complete dimension (rocmplet) indicates that the minimum dimension expressible in terms of the granule specified that completely covers the actual dimension will be reported. The value round off to maximum complete dimension (roscant) indicates that the maximum dimension expressible in terms of the granule specified that is fully occupied by the actual dimension will be reported. The value round off to dimension boundaries (roboundy) indicates that the dimension that places the boundaries of the reported dimension as close as possible to the boundaries of the actual dimension is reported.
NOTE 307 The use of recursive dimension references and selected components, in conjunction with marker functions, allows the specification of arbitrarily complex synchronization and alignment relationships. These tools allow applications to place and size events, modscopes, and proscopes in relation to other events, modscopes, and proscopes.
<!-- Explicit Dimension Reference -->
<![ %dimref; [
<!notation
dimref -- Explicit dimension reference marker function
notation --
-- Clause: 9.8.2.1 --
PUBLIC "ISO/IEC 10744:1997//NOTATION
Explicit dimension reference marker function notation//EN"
-- CommonAttributes [GenArc]: altreps, included, superdcn --
-- CommonAttributes [base]: bosdatt --
-- CommonAttributes [locs]: egrvplan --
>
<!element
dimref -- Explicit dimension reference --
-- Clause: 9.8.2.1 --
- O
(%HyCFC;)*
-- Attributes [sched]: dimref --
-- CommonAttributes [GenArc]: dafe, dvlatt, etfullnm, id,
ireftype, lextype, opacity --
-- CommonAttributes [base]: activity, conloc, dtxtatt, valueref --
-- CommonAttributes [locs]: refctl, refloc, reftype, rflocspn --
>
<!attlist
dimref -- Explicit dimension reference --
-- Clause: 9.8.2.1 --
HyBase NAME #FIXED markfun
notation NOTATION (dimref) #FIXED dimref
elemspec -- Element specified --
-- Element from which referenced dimension is
derived --
CDATA -- Reference --
-- Reftype: (baton|event|evgrp|evsched|extent|
extlist|fcs|modgrp|modscope|progrp|
proscope|wand) --
#REQUIRED
selcomp -- Selected component of dimension --
-- Dimension component of specified element to be
referenced.
first: First or lowest quantum
last: Last or highest quantum
qcnt: Quantum count --
(first|last|qcnt)
qcnt
flip -- Flip selected component --
-- Whether or not to invert the referenced dimension
component. Specifically:
noflip: First is reported as a positive
integer corresponding to the number
of the first quantum counting from
the beginning of the axis, last is
reported as a negative integer
corresponding to the number of the
last quantum counting from the end of
the axis, and qcnt is reported as a
positive integer.
flip: First is reported as a negative
integer corresponding to the number
of first quantum counting from the
end of the axis, last is reported as
a positive integer corresponding to
the number of the last quantum
counting from the beginning of the
axis, and qcnt is reported as a
negative integer. --
(flip|noflip)
noflip
schdspec -- Element with sched attribute form specified --
-- Establishes context in which extents are
interpreted: FCS, axis order, and HMU --
-- Constraint: Ignored if element specified is
evsched, wand, baton or fcs. --
CDATA -- Reference --
-- Reftype: (baton|evsched|wand)? --
#IMPLIED -- Default: dimref is treated as if the containing
element with the sched attribute form is
referenced by schdspec. --
-- Constraint: Required if elemspec is extent or
extlist. --
axisspec -- Axis specified --
-- Axis on which referenced dimension occurs --
NAME -- Lextype: AXISNM --
-- Constraint: must be valid axis name of FCS in
which the referenced dimension occurs. --
#IMPLIED -- Default: only axis --
dimnum -- Dimension number --
NUMBER -- Constraint: 1 = first dimension in order of
appearance on axis --
#IMPLIED -- Default: smallest dimension encompassing all
dimensions --
extnum -- Extent number --
NUMBER -- Constraint: 1 = first or only extent in order of
specification/appearance in document --
#IMPLIED -- Default: combination of all relevant extents --
granule -- Granule for reporting --
-- Granule for reporting referenced dimension --
CDATA -- Lextype: granule --
-- Constraint: granule must be defined in terms of
the same SMU as axis --
#IMPLIED -- Default: MDU of axis of referenced dimension --
roffgran -- Round off to granule handling --
-- Specifies how to handle roundoff.
roerr: Report error if rounding is required.
rocmplet: Round off to minimum complete
dimension; that is, minimum dimension
expressible in terms of the granule
specified that completely covers the
actual dimension.
roscant: Round off to maximum complete
dimension; that is, maximum dimension
expressible in terms of the granule
specified that is fully occupied by
the actual dimension
roboundy: Round off to dimension boundaries;
that is, dimension that places the
boundaries of the reported dimension
as close as possible to the
boundaries of the actual
dimension. --
(roboundy|rocmplet|roerr|roscant)
roboundy
dsdtypes -- Directly scheduled types for calculating
referenced dimension --
-- Types of directly scheduled elements to be taken
into account when calculating the referenced
dimension. --
CDATA -- Lextype: ("#ALL"|("#BATON"|"#EVENT"|"#EVGRP"|
"#EVSCHED"|"#EXTENT"|
"#EXTLIST"|"#FCS"|"#MODGRP"|
"#MODSCOP"|"#PROGRP"|
"#PROSCOP"|"#WAND"|GI)*) --
-- Constraint: GIs must be of event, modscope,
proscope, evgrp, modgrp, progrp, evsched, wand,
baton, or fcs form elements. --
#IMPLIED -- Default: Depends on form of element specified, as
follows:
element specified: default value:
- - - - - - - - - - - - - - - -
extent (null string)
extlist, event,
modscope or proscope "#EXTENT #EXTLIST"
evgrp or evsched "#EXTENT #EXTLIST #EVENT
#EVGRP"
modgrp or wand "#EXTENT #EXTLIST #MODSCOP
#MODGRP"
progrp or baton "#EXTENT #EXTLIST #PROSCOP
#PROGRP"
fcs "#ALL" --
>
<!entity % sched "INCLUDE">
]]><!-- dimref -->When the dimension referenced is derived from the dimensions of one or more indirectly scheduled (that is, projected) events, modscopes or proscopes, additional contextual information may be needed and additional constraints apply. The extents of the set of events, modscopes, and proscopes whose projected dimensions are being referenced are selected in the same way as if their directly scheduled dimensions were being referenced, using the elemspec, schdspec, extnum, and dsdtypes attributes. Also, the reporting of the referenced dimension is governed by the granule, roffgran, selcomp, and flip attributes in the same way as a directly scheduled dimension. However, the dimnum and axisspec attributes refer to the projected dimension number and the target axis, respectively, instead of the unprojected dimension number and the axis on which it was directly scheduled.
When the element specified is an evsched, wand, baton, or fcs, the attribute projected and/or direct (prjdirct) indicates whether the set of events, modscopes, and proscopes from which the referenced dimension is derived includes the events, modscopes, and proscopes that are directly scheduled in or by the element specified (drctonly), or only the dimensions of events, modscopes and proscopes that are projected on the element specified (projonly), or both (drctproj). The value of the prjdirct attribute is ignored if the element specified is an extent, extlist, event, modscope, proscope, evgrp, modgrp or progrp. If a value is specified for the extnum attribute, the value of the prjdirct attribute will be ignored, and the dimref will be treated as if the value of the prjdirct attribute were specified to be drctonly.
NOTE 308 Because extnum selects the unprojected referenced dimension according to its syntactic specification in the source document, extnum cannot be used to select extents that have been projected onto an fcs, evsched, wand, or baton that is the element specified by the elemspec attribute. The dimensions of such extents can be referenced by means of the dimnum attribute, in their order of appearance on an axis. Alternatively, they could be referenced by using the elemspec attribute to specify an element that would permit the selection of their unprojected extents.
NOTE 309 If the element specified is an evsched, wand, baton, or fcs, any events, modscopes, or proscopes that exist in it as a result of having been projected onto it will not be taken into account unless all of the kinds of elements that play a role in projecting such events, modscopes, or proscopes are specified in the value of the dsdtypes attribute. Specifying "#ALL" assures that all events, modscopes, and proscopes projected onto the element specified will be taken into account, regardless of which kinds of elements played a role in projecting them.
The attribute projected to target (prjtarg) specifies an element onto which the selected extent (or all of the specified extents if no value is specified for the extnum attribute) of the unprojected events, modscopes, and proscopes may have been projected. The prjtarg attribute may specify only one element, which must be an fcs, evsched, wand, or baton. If the element specified by the elemspec attribute is an extent or extlist, the value of the prjtarg attribute is ignored. If a value is specified for the prjtarg attribute and that value is not ignored:
The referenced dimension is the dimension of the selected extent (or all of the extents if no value is specified for the extnum attribute) of the unprojected events, modscopes, and proscopes selected for calculation of the unprojected referenced dimension, as projected onto the fcs, evsched, wand or baton specified by the prjtarg attribute, and subject to further selection by the prjby attribute (see below).
The value of the axisspec attribute must be a valid axis name of the target FCS. The referenced dimension occurs on that axis.
The value of the dimnum attribute does not select from the unprojected referenced dimensions; instead, it selects from the projected referenced dimensions.
The attribute projected by (prjby) limits the projections of the selected extent (or all of the extents if no value is specified for the extnum attribute) of the unprojected events, modscopes, and proscopes selected for calculation of the unprojected referenced dimension, as projected onto the fcs, evsched, wand or baton specified by the prjtarg attribute, that will be taken into account, to only those projections that are specified by the prorule, baton, progrp and proscope elements specified by the prjby attribute. If no value is specified for the prjby attribute, all projections specified by all relevant prorules, batons, progrps, and proscopes will be taken into account.
It is a reportable HyTime error if a non-ignored value is specified for the prjtarg attribute and the projection targets include more than one FCS.
NOTE 310 The value of the prjby attribute should be used in such a way as to avoid errors of this kind.
If no value is specified for the prjtarg attribute, or if the value of the prjtarg attribute is ignored, the value of the prjby attribute is ignored.
<!-- Projected Dimension Reference -->
<![ %dimref; %project; [
<!attlist
-- pdimref -- -- Projected dimension reference --
-- Clause: 9.8.2.2 --
-- Dimref attributes for references to projected
sets of events, modscopes and/or proscopes --
(dimref)
prjdirct -- Projected and/or direct --
-- Selection on the basis of whether events,
modscopes, or proscopes were either projected
onto, or directly scheduled in, the specified
element.
drctonly: Direct only
projonly: Projected only
drctproj: Direct and projected --
-- Constraint: Value is ignored if element specified
is not evsched, wand, baton, or fcs. --
-- Constraint: Value is ignored (is, in effect,
drctonly) if a value is specified for extnum. --
(drctonly|drctproj|projonly)
drctonly
prjtarg -- Projected to target --
-- Referenced dimension exists by projection onto
element specified by prjtarg attribute. --
-- Constraint: Value is ignored (and referenced
dimension is not a projected dimension) if
element specified is extent or extlist. --
CDATA -- Reference --
-- Reftype: (baton|evsched|fcs|wand) --
#IMPLIED -- Default: Referenced dimension is unprojected. --
prjby -- Projected by --
-- Referenced dimension exists by projection onto
element specified by prjtarg attribute only by
elements specified by prjby attribute. --
-- Constraint: Value is ignored unless prjtarg has
non-ignored value. --
CDATA -- Reference --
-- Reftype: (baton|progrp|prorule|proscope) --
#IMPLIED -- Default: All relevant prorules, batons, progrps,
and proscopes will be taken into account. --
>
]]><!-- dimref, project -->| Next Clause | Previous Clause |
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