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<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML Strict//EN">
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<TITLE>Architectural Form Processing</TITLE>
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<H1>Architectural Form Processing</H1>
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The Hytime standard (ISO/IEC 10744) introduced the concept of
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architectural forms. This document assumes you are already familiar
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with this concept. HyTime 2nd Edition generalizes this, and makes it
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possible to have an <I>architecture engine</I> which can perform
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architectural form processing for arbitrary architectures. SP
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includes such an architecture engine.
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Non-markup sensitive applications built using SP now support
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architectural form processing using the <SAMP>-A
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<VAR>archname</VAR></SAMP> option. When this option is specified, the
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document will be validated against all declared base architectures,
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and the output will be for the architectural document for that
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architecture: the element types, notations and attributes will be
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those defined in the meta-DTD.
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Although spam does not support the <SAMP>-A</SAMP> option because it
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works with the markup of your document, sgmlnorm does.
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<H2>Architectural Support Attributes</H2>
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To use the <SAMP>-A</SAMP> option with a document, you must add
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an architecture base declaration for <SAMP><VAR>archname</VAR></SAMP>,
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a notation declaration and associated attribute definition list
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declaration for <SAMP><VAR>archname</VAR></SAMP>;
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this is called the <I>architecture notation declaration</I>.
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An architecture base declaration is a processing instruction of the form:
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<?IS10744 ArcBase <VAR>archname</VAR>>
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The processing instruction is recognized either in the DTD or in an
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The architecture notation declaration and associated attribute
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definition list declaration serve to declare a number of architectural
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support attributes which control the architecture engine. The value
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for each architecture support attribute is taken from the default
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value, if any, specified for that attribute in the attribute
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definition list declaration. It is an error to declare an
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architecture support attribute as <SAMP>#REQUIRED</SAMP>.
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The following architectural support attributes are recognized:
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The name of an external entity that contains the meta-DTD.
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This attribute is required.
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If the name starts with the PERO delimiter <SAMP>%</SAMP>,
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the entity is a parameter entity,
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otherwise it is a general entity.
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A list of tokens that looks like what follows <SAMP>QUANTITY SGMLREF</SAMP>
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in the quantity set section of an SGML declaration.
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The quantities used for parsing the meta-DTD
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and validating the architectural document
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will be the maximum of the quantities in the document's concrete syntax
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and the quantities specified here.
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The name of the document element type in the meta-DTD.
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This would be <SAMP>HyDoc</SAMP> for HyTime.
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This defaults to <SAMP><VAR>archname</VAR></SAMP>.
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The name of the attribute that elements use to specify the
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corresponding element type, if any, in the meta-DTD.
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Data entities also use this attribute to specify the corresponding
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notation in the meta-DTD.
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This would be <SAMP>HyTime</SAMP> for HyTime.
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This defaults to <SAMP><VAR>archname</VAR></SAMP>.
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The name of the attribute that elements use to specify substitutes for
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the names of attributes in the meta-DTD. A value of
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<SAMP>#DEFAULT</SAMP> is allowed for a substitute name; this inhibits
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mapping of an attribute to an architectural attribute, but specifies
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that the value of the architectural attribute should be defaulted
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rather than taken from the value of another attribute in the document.
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For HyTime the value of this attribute would be <SAMP>HyNames</SAMP>.
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By default no attribute name substitutition is done.
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<SAMP>ArcSuprA</SAMP>
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The name of an attribute that elements may use to suppress processing
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of their descendants. This attribute is not recognized for data
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entities. The value of the attribute must be one of the following
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Completely suppress all architectural processing of descendants.
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It is not possible to restore architectural processing
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<SAMP>sArcForm</SAMP>
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Suppress processing of the <SAMP>ArcFormA</SAMP> attribute of all
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descendants of this element, except for those elements that have a
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non-implied <SAMP>ArcSuprA</SAMP> attribute.
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<SAMP>sArcNone</SAMP>
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Don't suppress architectural processing for the descendants of
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The value may also be implied, in which case the state of
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architectural processing is inherited.
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If an element has an ArcSuprA attribute that was processed, its
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ArcFormA attribute will always be processed. Otherwise its ArcFormA
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attribute will be processed unless its closest ancestor that has a
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non-implied value for the ArcSuprA attribute suppressed processing of
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the ArcFormA attribute. An element whose ArcFormA attribute is
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processed will not be treated as architectural if it has an implied
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value for the ArcFormA attribute.
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<SAMP>ArcSuprF</SAMP>
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The name of the element type in the meta-DTD that suppresses
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architectural processing in the same manner as does the
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<SAMP>sHyTime</SAMP> form in HyTime. By default, no element type
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does. This behaves like an element with an
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<SAMP>ArcSuprA</SAMP> attribute of <SAMP>sArcForm</SAMP>. The element
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type should be declared in the meta-DTD. You should not specify a
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value for this attribute if you specified a value for the
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<SAMP>ArcSuprA</SAMP> attribute.
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This is a non-standardized extension.
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<SAMP>ArcIgnDA</SAMP>
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The name of an attribute that elements may use to control whether
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The value of the attribute must be one of the following values:
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<SAMP>nArcIgnD</SAMP>
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It is an error if data occurs where not allowed by the meta-DTD.
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<SAMP>cArcIgnD</SAMP>
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Data is conditionally ignored.
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Data will be ignored only when it occurs where the meta-DTD
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Data is always ignored.
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The value may also be implied, in which case the state of
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architectural processing is inherited.
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If no the document element has no value specified,
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<SAMP>cArcIgnD</SAMP> will be used.
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<SAMP>ArcBridF</SAMP>
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The name of a default element type declared in a meta-DTD,
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to which elements in the document should be automatically mapped
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if they have an ID and would not otherwise be considered
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This would be <SAMP>HyBrid</SAMP> for HyTime.
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If your meta-DTD declares IDREF attributes, it will
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usually be appropriate to specify a value for
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<SAMP>ArcBridF</SAMP>, and to declare an ID attribute
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for that form in your meta-DTD.
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<SAMP>ArcDataF</SAMP>
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The name of a default notation declared in the meta-DTD,
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to which the external data entities in the document
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should be automatically mapped if they would
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not otherwise be considered architectural.
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If this attribute is defined,
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then general entities will be automatically architectural:
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any external data entity whose notation cannot otherwise be mapped
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into a notation in the meta-DTD will be automatically treated
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as an instance of the <SAMP>ArcDataF</SAMP> notation.
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This would be <SAMP>data</SAMP> for HyTime.
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If your meta-DTD declares entity attributes, it will usually
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be appropriate to specify a value for <SAMP>ArcDataF</SAMP>
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even if your meta-DTD declares no data attributes for the
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This must have one of the following values:
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If an element does not have an <SAMP>ArcFormA</SAMP> attribute and the
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meta-DTD defines an element type with the same name as the element's
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type, the element will be automatically treated as being an instance
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of the meta-type. This rule does not apply to the
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document element type; this is automatically treated as being an
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instance of the meta-DTD's document element type.
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Note that this automatic mapping is prevented if
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the element has an <SAMP>ArcFormA</SAMP> attribute with an implied
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value. It is also prevented if processing of the
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<SAMP>ArcFormA</SAMP> attribute is suppressed. This applies equally
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to the notations of external data entities.
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The default element or notation specified with the
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<SAMP>ArcBridF</SAMP> or <SAMP>ArcDfltN</SAMP> attribute
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is only considered after the mapping specified by <SAMP>ArcAuto</SAMP>.
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<SAMP>nArcAuto</SAMP>
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Automatic mapping is not performed.
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The default value is <SAMP>ArcAuto</SAMP>.
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<SAMP>ArcOptSA</SAMP>
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A list of names of architectural support attributes,
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each of which is interpreted as a list of parameter entities
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to be defined with a replacement text of <SAMP>INCLUDE</SAMP>
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when parsing the meta-DTD.
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The default value is <SAMP>ArcOpt</SAMP>.
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A meta-DTD is allowed to use the following extensions:
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a single element type or notation is allowed to be an associated
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element type or associated notation name for multiple attribute
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<SAMP>#ALL</SAMP> can be used as an associated element type
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or associated notation name in an attribute definition list
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to define attributes for all element types or notations
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Before any of these extensions can be used, the meta-DTD must include a
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<!AFDR "ISO/IEC 10744:1997">
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This declaration should only be included if the extensions are used.
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In all other respects a meta-DTD must be a valid SGML DTD.
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A declared value of ENTITY for an attribute in a meta-DTD means that
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the value of the attribute must be an entity declared in
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the (non-meta) DTD that is architectural.
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An external data entity is architectural only if its notation can be
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mapped into a notation in the meta-DTD.
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All other kinds of data entities and subdoc entities are automatically
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An IDREF attribute in the meta-document must have a corresponding ID
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in the meta-document. An attribute with a declared value of ID in the
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document will be automatically mapped to an attribute with a declared
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value of ID in the meta-DTD.
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A declared value of NOTATION in the meta-DTD means that the value of
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the attribute must have one the values specified in the name group and
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that it must be a notation in the meta-DTD.
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(Perhaps if the attribute also has a declared value of NOTATION
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in the non-meta-DTD, the value should be mapped in a similar
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way to the notation of an external data entity.)
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<H2>Differences from HyTime</H2>
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There are a number of differences from how architectural processing is
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defined in the pre-Corringendum version of the HyTime standard.
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The <SAMP>ArcNamrA</SAMP> and <SAMP>ArcFormA</SAMP> attributes are not
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part of the meta-DTD. Rather they are used by the architecture engine
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in deriving the meta-document that is validated against the meta-DTD.
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The <SAMP>use:</SAMP> conventional comment is not recognized. Instead
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a single element type is allowed to be an associated element type for
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multiple attribute definition lists.
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The notation and data attributes of an external data entity are
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treated just like the element type and attributes of an element. The
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notation of an external data entity is mapped into a notation in the
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meta-DTD and the data attributes of the entity are mapped onto
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attributes defined for the meta-DTD notation.
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<SAMP>#FIXED</SAMP> has the same meaning in a meta-DTD that it does in
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a regular DTD: the value of the attribute must be the same as the
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default value of the attribute specified in the meta-DTD.
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<H2>Specifying architectural processing with an LPD</H2>
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Link attributes defined by an implicit link process are treated in the
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same way as non-link attributes. The only complication is that SGML
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allows link attributes to have the same name as non-link attributes.
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If there is a link attribute and a non-link attribute with the same
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name, the architecture engine will only look at the link attribute,
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even if the value of the link attribute is implied. The only
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exception is the <SAMP>ArcNamrA</SAMP> attribute: the architecture
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engine will use both the link attribute and the non-link attribute,
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but the substitute names in the value of the non-link attribute cannot
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refer to link attribute names.
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The <SAMP>-A <VAR>archname</VAR></SAMP> option automatically activates
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any link type <SAMP><VAR>archname</VAR></SAMP>.
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The architecture notation declaration and associated attribute
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definition list declaration are allowed in the LPD. Although the
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productions of ISO 8879 do not allow a notation declaration in a link
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type declaration subset, it is clearly the intent of the standard that
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they be allowed. You can use a <SAMP>-wlpd-notation</SAMP> option to
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<H2>Derived architectures</H2>
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A meta-DTD can have one or more base architectures in the same way as
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a normal DTD. Multiple <SAMP>-A</SAMP> options can be used to exploit
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-A <VAR>arch1</VAR> -A <VAR>arch2</VAR>
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will perform architectural processing on the source document to
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produce an architectural document conforming to the architecture
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<SAMP><VAR>arch1</VAR></SAMP> declared in the source document, and
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will then perform architectural processing on this architectural
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document to produce an architectural document conforming to the
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<SAMP><VAR>arch2</VAR></SAMP> architecture declared in
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<SAMP><VAR>arch1</VAR></SAMP>'s meta-DTD.
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A document that is validated against a meta-DTD will automatically
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be validated against any base architectures of that meta-DTD.
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<H2><A NAME=hi2diff>Unimplemented features</A></H2>
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The following features from the AFDR specification in HyTime 2nd
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edition are not yet implemented:
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use of <CODE>#MAPTOKEN</CODE> in the architectural attribute renamer.
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doc/archform.htm
