Topic Maps
- Canonicalization
ISO (the International Organization for Standardization) and
IEC (the International Electrotechnical Commission) form the
specialized system for worldwide standardization. National bodies
that are members of ISO or IEC participate in the development of
International Standards through technical committees established by
the respective organization to deal with particular fields of
technical activity. ISO and IEC technical committees collaborate in
fields of mutual interest. Other international organizations,
governmental and non-governmental, in liaison with ISO and IEC, also
take part in the work. In the field of information technology, ISO and
IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the
rules given in the ISO/IEC Directives, Part 2.
ISO/IEC 13250-4
was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information Technology, Subcommittee SC 34, Document
Description and Processing Languages.
ISO/IEC 13250
consists of the following parts, under the
general title Topic Maps:
- Part 1:
Overview and Basic Concepts
- Part 2:
Data Model
- Part 3:
XML Syntax
- Part 4:
Canonicalization
- Part 5:
Reference Model
- Part 6:
Compact Topic Maps Syntax
- Part 7:
Graphical Notation
This part of ISO/IEC13250 defines a format known as Canonical XTM, or CXTM for short.
The format is an XML format, and has the property that it guarantees
that two equivalent Topic Maps Data Model instances [ISO/IEC 13250-2]
will always produce byte-by-byte identical serializations on disk, and
that non-equivalent instances will always produce different
serializations. CXTM thus enables direct comparison of two topic maps
to determine equality by comparison of their canonical serializations.
The purpose of CXTM is to allow the creation of test suites for
various Topic Maps-related technologies that are easily portable
between different Topic Maps implementations, so long as these support
CXTM.
CXTM is not intended to be used for the interchange of topic
maps, although this is possible. The standard format for interchange
of topic maps is XTM [ISO/IEC 13250-3].
Topic Maps
- Canonicalization
This part of ISO/IEC13250 defines the CXTM format, and specifies how CXTM files are
produces from topic maps by means of a transformation from the Topic
Maps Data Model [ISO/IEC 13250-2] to the XML Infoset [XML Infoset].
The following referenced documents are indispensable for the
application of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the
referenced document (including any amendments) applies.
NOTE:
Each of the following documents has a unique identifier that is
used to cite the document in the text. The unique identifier consists
of the part of the reference up to the first comma.
ISO/IEC 10646-1, ISO/IEC 10646-1:2000: Information technology -
Universal Multiple-Octet Coded Character Set (UCS) -
Part 1: Architecture and Basic Multilingual Plane, ISO, 2000
ISO/IEC 10646-2, ISO/IEC 10646-2:2001 Information technology - Universal Multiple-Octet
Coded Character Set (UCS) - Part 2: Supplementary Planes, ISO, 2001
Unicode, The Unicode Standard, Version 5.0.0, The Unicode Consortium, Reading, Massachusetts, USA, Addison-Wesley Developer's Press, 2007, ISBN 0-321-48091-0, http://www.unicode.org/versions/Unicode5.0.0/
RFC 3986, Uniform Resource Identifiers (URI): Generic Syntax, Internet Standards Track Specification, January 2005, http://www.ietf.org/rfc/rfc3986.txt
RFC 3987, Internationalized Resource Identifiers (IRIs), Internet Standards Track Specification, January 2005, http://www.ietf.org/rfc/rfc3987.txt
XML-C14N, Canonical XML, Version 1.0, World Wide Web Consortium, 15th March 2001, http://www.w3.org/TR/2001/REC-xml-c14n-20010315
XML Infoset, XML Information Set, World Wide Web Consortium, 24 October 2001, http://www.w3.org/TR/2001/REC-xml-infoset-20011024
ISO/IEC 13250-2, ISO/IEC 13250-2:2006 Information technology - Topic Maps - Data model
The canonicalization process takes two parameters: a topic map (that
is, an instance of the Topic Maps Data Model [ISO/IEC 13250-2]) and a
base locator. The process produces a canonicalization of the topic
map, with all locators in the topic map rewritten to be relative to
the given base locator.
Canonicalization is performed in two steps:
-
A document information item representing the CXTM document is
produced from the TMDM instance as described in
3.3.
-
The document information item is serialized to a Canonical XML
representation as described in [XML-C14N].
Information item properties from [W3C XML-Infoset] are referred to using [[property name]], in order to distinguish them from
properties from [ISO/IEC 13250-2].
Ed. Note:
People found this confusing in 13250-3, because they couldn't tell
which properties were XML properties and which were TMDM properties.
Should we use the same convention as 13250-3, that is, [[property]]
for XML properties?
Throughout the rest of this clause the value of the [parent]
property of element information items and attribute information items
is not specified. The [parent] property of an element information item
must always be set to the element or document information item of
which the element information item is a direct child. The [parent]
property of an attribute information item must be set to the element
information item of which the attribute is a child.
Ed. Note:
This duplicates text in 3.20 and 3.21. Do we really need it both places?
There is exactly one CXTM document information item in the XML
Infoset generated by the canonicalization of the Topic Maps Data
Model.
The CXTM document information item has the following
properties:
-
[[children]] A list containing only the representation of the topic
map information item in the Topic Maps Data Model instance
-
[[document element]] The element information item that represents the
topic map information item in the Topic Maps Data Model instance
-
[[notations]] The empty set
-
[[unparsed entities]] The empty set
-
[[base URI]] No value
-
[[standalone]] No value
-
[[version]] No value
-
[[all declarations processed]] False
A topic map information item in the Topic Maps Data Model is
represented by an element information item with the following
properties:
-
[[local name]] The string "topicMap"
-
[[children]] A list of element information items in the
following order:
-
If the value of the [item identifiers] property of the topic map
information item is not the empty set, then a representation of
the [item identifiers] property
-
A representation of each topic information item in the [topics]
property of the topic map information item in canonical sort
order
-
A representation of each association information item in the
[associations] property of the topic map information item in
canonical sort order
-
[[attributes]] If the value of the [reifier] property is not null,
then a representation of the [reifier] property otherwise
the empty set
A topic item is represented by an element information item in the XML
Infoset. The element information item has the following properties.
-
[[local name]] The string "topic"
-
[[children]] A list of element information items in the following
order:
-
If the value of [subject identifiers] property of the topic
item is not the empty set, then an element information item
with the following properties:
-
[[local name]] The string "subjectIdentifiers"
-
[[children]] A representation of each of the locator of
the [subject identifiers] property in canonical sort order
-
[[attributes]] An empty list
-
If the value of the [subject locators] property of the topic
item is not the empty set, then an element information
item with the following properties:
-
[[local name]] The string "subjectLocators"
-
[[children]] A representation of each of the locator of
the [subject locators] property in canonical sort order
-
[[attributes]] An empty list
-
If the value of the [item identifiers] property of the topic
item is not the empty set, then a representation of the
[item identifiers] property
-
A representation of each of the topic name items of the
[topic names] property in canonical sort order
-
A representation of each of the occurrence items of the
[occurrences] property in canonical sort order
-
For each of the association role items of the [roles played]
property in canonical sort order, an element information item
with the following properties
-
[[local name]] set to the string "rolePlayed"
-
[[children]] An empty list
-
[[attributes]] A list containing the following attribute
information items:
-
[[local name]] set to the string "ref"
-
[[normalized value]] A sequence of character information
items representing a string value constructed by the
concatenation of:
-
The string "association."
-
The position of the association item which is the
value of the [parent] property of the association role
item, in the canonically sorted [associations] property
of the parent topic map item
NOTE:
The position is converted from an integer to a string.
-
The string ".role."
-
The position of the reified
association role item in the canonically
sorted [roles] property of the parent
association item
-
[[attributes]] If the value of the [reified] property is not null,
then a representation of the [reified] property, otherwise an
empty list
Each topic name item in the Topic Maps Data Model is represented by an
element information item with the following properties.
-
[[local name]] The string "topicName"
-
[[children]] A list of element information items in the following
order:
-
A representation of the [value] property
-
If the value of the [type] property is not null, a
representation of the [type] property
-
If the value of the [scope] property is not the empty set,
a representation of the [scope] property.
-
A representation of each of the variant items of the
[variants] property in canonical sort order
-
If the value of the [item identifiers] property is not the
empty set, a representation of the [item identifiers]
property
-
[[attributes]] If the value of the [reifier] property is not null,
a representation of the [reifier] property otherwise an empty
list
A variant item in the Topic Maps Data Model is represented by an
element information item with the following properties:
-
[[local name]] The string "variant"
-
[[children]] A list of element information items in the following
order:
-
If the value of the [value] property is not null,
a representation of the [value] property
-
If the value of the [datatype] property is not null, a
locator identifying the datatype of the [value] property
-
If the value of the [scope] property is not the empty set, a
representation of the [scope] property
-
If the value of the [item identifiers] property is not the
empty set, a representation of the [item identifiers] property
-
[[attributes]] If the value of the [reifier] property is not null,
then a representation of the [reifier] property otherwise an empty
list
An occurrence item in the Topic Maps Data Model is represented by an
element information with the following properties:
-
[[local name]] The string "occurrence"
-
[[children]] A list of element information items in the following
order:
-
If the value of the [value] property is not null,
a representation of the [value] property
-
If the value of the [datatype] property is not null, a
locator identifying the datatype of the [value] property
-
If the value of the [type] property is not null, a
representation the [type] property
-
If the value of the [scope] property is not the empty set, a
representation of the [scope] property
-
If the value of the [item identifiers] property is not the
empty set, a representation of the [item identifiers] property
-
[[attributes]] If the value of the [reifier] property is not null, a
representation of the [reifier] property otherwise an empty list
An association item in the Topic Maps Data Model is represented by an
element information item with the following properties:
-
[[local name]] The string "association"
-
[[children]] A list of element information items in the
following order:
-
If the value of the [type] property is not
null, a representation of the [type] property
-
A representation of each of the items of the [roles]
property in canonical sort order
-
If the value of the [scope] property is not the empty set, a
representation of the [scope] property
-
If the value of the [item identifiers] property is not the
empty set, a representation of the [item identifiers] property.
-
[[attributes]] If the value of the [reifier] property is not null,
then a representation of the [reifier] property otherwise an empty
list
An association role item in the Topic Maps Data Model is represented by
an element information item with the following properties:
-
[[local name]] The string "role"
-
[[children]] A list of element information items in the following
order
-
An element information item with the following properties:
-
[[local name]] The string "player"
-
[[children]] The empty list
-
[[attributes]] A list containing one attribute information
item with the following properties:
-
[[local name]] The string "topicref"
-
[[normalized value]] The position of the topic
information item that is the value of the encoded
property within the canonically sorted list of all
topic items in the Topic Maps Data Model being encoded
-
If the value of the [type] property is not null, a
representation of the [type] property
-
If the value of the [item identifiers] property is not the empty
set, a representation of the [item identifiers] property
-
[[attributes]] If the value of the [reifier] property is not null, a
representation of the [reifier] property otherwise an empty list
The [reifier] property of a topic map item, topic name item, variant
item, occurrence item, association item or association role item is
represented as an attribute information item with the following
properties:
-
[[local name]] The string "reifier"
-
[[normalized value]] The position of the topic item that is the
value of the [reifier] property in the canonically sorted list of
all topic items in the Topic Maps Data Model being encoded
The [reified] property of a topic item is represented as an
attribute information item with the following properties:
-
[[local name]] The string "reified"
-
[[normalized value]] A sequence of character information items
representing a string value constructed as follows:
-
If the value of the [reified] property is the topic map item,
then the string "topicMap"
-
If the value of the [reified] property is a topic name item,
then a concatenation of:
-
The string "topic."
-
The position of the topic item, which is the value of the
[parent] property of the reified topic name item, within
the canonically sorted list of all topic items
-
The string ".name."
-
The position of the topic name item in the canonically
sorted [names] property of the parent topic item
-
If the value of the [reified] property is a variant item,
then a concatenation of:
-
The string "topic."
-
The position of the topic item, which is the value of the
[parent] property of the topic name item which is the value
of the [parent] property of the reified variant item,
within the canonically sorted list of all topic items
-
The string ".name."
-
The position of the topic name item, which is the value of
the [parent] property of the reified variant item, in the
canonically sorted [names] property of the parent topic
item.
-
The string ".variant."
-
The position of the variant item in the canonically sorted
[variants] property of the parent topic name item
-
If the value of the [reified] property is a occurrence item,
then a concatenation of:
-
The string "topic."
-
The position of the topic item, which is the value of the
[parent] property of the reified occurrence item, within
the canonically sorted list of all topic items
-
The string ".occurrence."
-
The position of the occurrence item in the canonically
sorted [occurrences] property of the parent topic item
-
If the value of the [reified] property is a association item,
then a concatenation of:
-
The string "association."
-
The position of that association item in the canonically
sorted [associations] property of the parent topic map
item
-
If the value of the [reified] property is an association role
item, then a concatenation of:
-
The string "association."
-
The position of the association item, which is
the value of the [parent] property of the reified
association role item, in the canonically sorted
[associations] property of the parent topic map item
-
The string ".role."
-
The position of the reified association role item in the
canonically sorted [roles] property of the parent
association item
The [scope] property of a topic name item, variant item,
occurrence item or association item is represented by an element
information item with the following properties:
-
[[local name]] The string "scope"
-
[[children]] A list of one element information item for each topic
item in the value of the [scope] property in canonical sort order.
Each element information item has the following properties:
-
[[local name]] The string "scopingTopic"
-
[[children]] An empty list
-
[[attributes]] A list containing a single attribute information
item with the following properties:
-
[[local name]] The string "topicref"
-
[[normalized value]] The
position of the topic item within the canonically sorted
list of all topic items in the Topic Maps Data Model being
encoded
-
[[attributes]] An empty list
The [item identifiers] property of an information item in the
Topic Maps Data Model is represented by an element information
item with the following properties:
-
[[local name]] The string "itemIdentifiers"
-
[[children]] A representation of each of the locator of
the [item identifiers] property in canonical sort order
-
[[attributes]] An empty list
The [datatype] property of a variant item or occurrence item is
represented by an element information
item with the following properties:
-
[[local name]] The string "datatype"
-
[[children]] An empty list
-
[[attributes]] A list containing an attribute information item with
the following properties:
-
[[local name]] The string "locator"
-
[[normalized value]] A normalized locator that identifies data type.
The [type] property of a topic name item, occurrence item, association
item or association role item is represented by an element information
item with the following properties:
-
[[local name]] The string "type"
-
[[children]] An empty list
-
[[attributes]] A list containing an attribute information item with
the following properties:
-
[[local name]] The string "topicref"
-
[[normalized value]] The position of
the topic item that is the value of the [type] property within
the canonically sorted list of all topic items in the Topic
Maps Data Model being encoded.
A [value] property in the Topic Maps Data Model is represented by an
element information item with the following properties:
-
[[local name]] The string "value"
-
[[children]] A sequence of character information items
representing the string value of the [value] property
-
[[attributes]] An empty list
Before encoding a string property as a sequence of character
information items, the string must be normalised according to Unicode
Normalization Form C (Unicode Standard Annex #15, Unicode
Normalization Forms, [Unicode]). Each character information
item must have the following properties:
-
[[character code]] The ISO 10646 ([ISO/IEC 10646-1] and
[ISO/IEC 10646-2]) character code for the character.
-
[[element content whitespace]] unknown for whitespace characters
(characters with character codes #x20, #x9, #xD and #xA), and
false for all other characters.
-
[parent] the containing element or attribute information
item.
Ed. Note:
Should we get rid of the Unicode normalization?
Ed. Note:
Don't we know for certain that whitespace is not element content
whitespace in CXTM?
When the position of an item in a list is to be encoded, the
encoded value is the index of that item in the list counting from 1 as
the index of the first list item.
All element information items created by the canonicalization
process must have the following property values:
-
[[namespace name]] No value
-
[[prefix]] No value
-
[[namespace attributes]] The empty set
-
[[in-scope namespaces]] The empty set
-
[[base URI]] No value
-
[parent] The element information item or document information
item of which the element is a direct child
All attribute information items created by the canonicalization
process must have the following property values:
-
[[namespace name]] No value
-
[[prefix]] No value
-
[[attribute type]] unknown
-
[[references]] unknown
-
[[specified]] the boolean value true
-
[[owner element]]the element information item that this
attribute information item belongs to
When transforming an instance of the Topic Maps Data Model to an
instance of the XML Infoset model, all properties in the Topic Maps
Data Model which are sets of information items must be encoded in the
XML Infoset model by encoding each set element in the canonical sort
order for the set. The clauses 4.2 to 4.11 define the canonical sort order for each
information item type.
The following sort order applies to all information items and all
instances of the basic types defined by the Topic Maps Data Model.
-
Null
-
string
-
set
-
locator
-
topic map
-
topic
-
topic name
-
variant
-
occurrence
-
association
-
association role
String values are compared on a character by character basis from
the start of the string to the end. When the first pair of characters
with different character codes are found, then the string containing
the character with the lower code sorts lower than the string
containing the character with the higher code. If all pairs compare
equal, but one string is shorter than the other, the shortest string
sorts lower than the longest string. If no differences are found the
two strings are considered equal.
Ed. Note:
Do we need to consider Unicode normalization here?
-
Sets sort in order of the number of elements in the collection. A
set with fewer elements sorts lower than a set with more elements.
-
For sets of equal size, first sort the elements of each set into
their canonical ordering. Starting with the lowest element in
each sorted set, perform a pair-wise comparison of element in
each collection until a non-equal comparison is found. The
collections then sort in the order of the non-equal elements in
each collection.
-
Sets with exactly the same elements will be considered
equal.
Locators are compared in the same way as strings (see
4.3.
Topic items are compared by comparing their properties in the
following order.
-
[subject identifiers]
-
[subject locators]
-
[item identifiers]
NOTE:
A combination of these three properties are all that is required to
compare two topics. Part 2 of this standard requires that all topic
items have at least one value for one of these properties and should
two topics match in any one of these three properties, they must be
merged.
Topic name items are compared by comparing their properties in
the following order.
-
[value]
-
[type]
-
[scope]
-
[parent]
Variant items are compared by comparing their properties in the
following order.
-
[value]
-
[datatype]
-
[scope]
-
[parent]
Occurrence items are compared by comparing their properties in the
following order.
-
[value]
-
[datatype]
-
[type]
-
[scope]
-
[parent]
Association items are compared by comparing their properties in the
following order.
-
[type]
-
[roles]
-
[scope]
-
[parent]
Association role items are compared by comparing their properties
in the following order.
-
[player]
-
[type]
-
[parent]
Ed. Note:
This must be completely rewritten.
Whenever the [reference] property of the locator item is used for
comparison or for creating values in the XML Infoset instance created
by the canonicalization process, it must be first converted to a
normalised form.
In the following description of the normalisation procedure for the
[reference] property of a locator item, the terms "fragment
identifier", "query" and "path segment" are defined in [RFC 3986]
The process of converting the value of the [reference] property of the
locator item to its normalised form is as follows:
-
Let the value P be the value of the [reference] property of the
locator item with any fragment identifier and query removed and any
trailing "/" character removed.
-
If the value of the [reference] property starts with P, then
the normalised value of the [reference] property is the substring
starting from, and including, the character immediately following
the string that matches P, with any leading "/" character removed.
-
If the value of the [reference] property does not start with P
and P can be interpreted as a URI with at least one path segment,
then remove the last path segment from P and any trailing "/"
character and repeat from step (2).
-
If the value of the [reference] property is not modified by
the steps above, then the value of the [reference] property is
the normalised value of the property.
NOTE:
This process may result in the value of the [reference] property no
longer being a syntactically valid or resolvable URI, however the CXTM
process described by this part of ISO/IEC13250 does not require a conforming application
to dereference these addresses.
topicMap =
element topicMap {
attlist.reifier, topic*, association*
}
attlist.reifier &=
attribute reifier { xsd:integer }?
topic = element topic {
attlist.reified,
subjectIdentifiers?,
subjectLocators?,
itemIdentifiers?,
topicName*,
occurrence*,
rolePlayed*
}
attlist.reified &=
attribute reified { text }?
subjectIdentifiers = element subjectIdentifiers {
locator+
}
subjectLocators = element subjectLocators {
locator+
}
itemIdentifiers = element itemIdentifiers {
locator+
}
topicName = element topicName {
attlist.reifier, value, type?, scope?, variant*, itemIdentifiers?
}
variant = element variant {
attlist.reifier, value?, datatype?, scope?, itemIdentifiers?
}
occurrence = element occurrence {
attlist.reifier, value?, datatype?, type?, scope?, itemIdentifiers?
}
rolePlayed = element rolePlayed {
attribute ref { text }
}
association = element association {
attlist.reifier, type?, role*, scope?, itemIdentifiers?
}
role = element role {
attlist.reifier, player?, type?, itemIdentifiers?
}
player = element player {
attlist.topicref
}
attlist.topicref &=
attribute topicref {xsd:integer}
value = element value { text }
type = element type { attlist.topicref }
locator = element locator {
attlist.locator
}
attlist.locator &=
attribute notation { xsd:string },
attribute address { xsd:string }
scope = element scope {
scopingTopic+
}
scopingTopic = element scopingTopic {
attlist.topicref
}
datatype = element datatype {
attlist.locator
}
start = topicMap
|
ISO/IEC 13250:2003, ISO/IEC 13250:2003: Information technology - Document
Description and Processing Languages - Topic Maps
, ISO, 2003
ISO/IEC 13250-3, ISO/IEC 13250-3: Information technology - Document
Description and Processing Languages - Topic Maps
- XML Syntax
, ISO, 2007
