ISO/IEC JTC 1/SC 34N0935

ISO/IEC JTC 1/SC 34

Information Technology --
Document Description and Processing Languages

TITLE:	Draft 13250-6 Topic Maps -- Compact Syntax
SOURCE:	Mr. Lars Heuer; Mr. Gabriel Hopmans; Dr. Sam Gyun Oh
PROJECT:	WD 13250-6: Information technology - Topic Maps - Compact syntax
PROJECT EDITOR:	Mr. Lars Heuer; Mr. Gabriel Hopmans; Dr. Sam Gyun Oh; Mr. Steve Pepper
STATUS:	Draft
ACTION:	Review
DATE:	2007-11-16
DISTRIBUTION:	SC34 and Liaisons
REPLY TO:	Dr. James David Mason (ISO/IEC JTC 1/SC 34 Chairman) Y-12 National Security Complex Bldg. 9113, M.S. 8208 Oak Ridge, TN 37831-8208 U.S.A. Telephone: +1 865 574-6973 Facsimile: +1 865 574-1896 Network: [email protected] http://www.y12.doe.gov/sgml/sc34/ ftp://ftp.y12.doe.gov/pub/sgml/sc34/ Mr. G. Ken Holman (ISO/IEC JTC 1/SC 34 Secretariat - Standards Council of Canada) Crane Softwrights Ltd. Box 266, Kars, ON K0A-2E0 CANADA Telephone: +1 613 489-0999 Facsimile: +1 613 489-0995 Network: [email protected] http://www.jtc1sc34.org

Topic Maps — Compact Syntax

Contents

Foreword

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 13250-6 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 Syntax
• Part 7: Graphical Notation

Introduction

CTM (Compact Topic Maps) is a text-based notation for representing topic maps. It provides a simple, lightweight notation that complements the existing XML-based interchange syntax defined in [XTM] and can be used for

• manually authoring topic maps;

• providing human-readable examples in documents;

• serving as a common syntactic basis for TMCL and TMQL.

The principal design criteria of CTM are compactness, ease of human authoring, maximum readability, and comprehensiveness rather than completeness. CTM supports all constructs of the [TMDM], except item identifiers on constructs that are not topics.

This part of ISO/IEC13250 should be read in conjunction with [TMDM] since the interpretation of the CTM syntax is defined through a mapping from the syntax to the data model there defined.

Topic Maps — Compact Syntax

1 Scope

This part of ISO/IEC13250 defines a text-based notation for representing instances of the data model defined in [TMDM]. It also defines a mapping from this notation to the data model. The syntax is defined through an EBNF grammar.

2 Normative references

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.

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/

XML 1.0, Extensible Markup Language (XML) 1.0, W3C, Third Edition, W3C Recommendation, 04 February 2004, http://www.w3.org/TR/REC-xml/

TMDM, ISO 13250-2 Topic Maps — Data Model, ISO, 2006, Lars Marius Garshol, Graham Moore, http://www.isotopicmaps.org/sam/sam-model/

XTM, ISO 13250-3 Topic Maps — XML Syntax, ISO, 2006, http://www.isotopicmaps.org/sam/sam-xtm/

XSDT, XML Schema Part 2: Datatypes Second Edition, W3C, W3C Recommendation, 28 October 2004, http://www.w3.org/TR/xmlschema-2/

RFC3986, RFC 3986 - Uniform Resource Identifiers (URI): Generic Syntax, T. Berners-Lee, R. Fielding, L. Masinter, 2005, http://www.ietf.org/rfc/rfc3986

RFC3987, RFC3987 - Internationalized Resource Identifiers (IRIs), M. Duerst, M. Suignard, 2005, http://www.ietf.org/rfc/rfc3987.txt

3 Syntax description

3.1 About the syntax

The acronym CTM is often used to refer to the syntax defined in this part of ISO/IEC13250. Its full name is Compact Topic Maps Syntax.

This clause defines the syntax of CTM documents using an EBNF grammar based on the notation described in [XML 1.0]. It also defines the semantics of such documents using prose that specifies the mapping from CTM documents to [TMDM]. The full EBNF can be found in Annex A.

3.2 Deserialization

The process of exporting a topic map from an implementation's internal representation of the data model to an instance of a Topic Maps syntax is known as serialization. The opposite process, deserialization, is the process of building an instance of an implementation's internal representation of the data model from an instance of a Topic Maps syntax.

This clause defines how instances of the CTM syntax are deserialized into instances of the data model defined in [TMDM]. Serialization is only implicitly defined, but implementations should guarantee that for any data model instance the CTM serialization produced by the implementation should, when deserialized to a new data model instance, produce one that has the same canonicalization as the original data model instance, according to [ISO 13250-4].

The input to the deserialization process is:

• A byte stream which is converted into a character stream.

  This character stream is processed according to the grammar specified by this part of ISO/IEC13250.

• An absolute IRI. This is the IRI from which the byte stream was retrieved, known as the document IRI. This IRI shall always be provided, as it is necessary in order to assign the item identifiers of the topic items created during deserialization. If the CTM document was not read from any particular IRI the application is responsible for providing an IRI considered suitable.

Deserialization is performed by processing each component of the document in document order. Components are defined in terms of text that matches a syntactic variable of the EBNF. For each component encountered the operations specified in the clause for the corresponding syntactic variable are performed.

Whenever a new information item is created, those of its properties which have set values are initialized to the empty set; all other properties are initialized to null.

Each CTM processor shall be aware of the following prefixes

xs

http://www.w3.org/2001/XMLSchema#

This is the namespace for the XML Schema Datatypes.

ctm

http://www.topicmaps.org/ctm/

This is the namespace for this part of ISO/IEC13250

3.3 Common syntactical constructs

3.3.1 Whitespace

Whitespace consists of one or more space (#x20) characters, carriage returns, line feeds, or tabs.

Space (#x20) characters are allowed everywhere to separate tokens (terminals and non-terminals).

3.3.2 Comments

Comments are fragments of the character stream which are ignored by a CTM processor. Comments are allowed where whitespace characters are allowed.

Multiline comments are delimited with (: and :). These kind of comments shall not be nested.

Single line comments are introduced by a hash (#) and continue until the end of the current line, or until the end of the character stream, whichever comes first.

3.3.3 Creating IRIs from strings

The delimiters < and > are removed from the string. The string within the delimiters may represent either an absolute or a relative IRI.

To create an IRI from a string, unescape the string by replacing %HH escape sequences with the characters they represent, and decode the resulting character sequence from UTF-8 to a sequence of abstract Unicode characters. The resulting string is turned into an absolute IRI by resolving it against the document IRI.

3.3.4 Creating IRIs from QNames

QNames are used to abbreviate IRIs. They are declared as follows:

A QName causes a locator to be created. During deserialization, the IRI to which the prefix is bound is concatenated with the local part. The result of such a process is always an absolute IRI.

If the prefix has not been bound to an IRI as specified in 3.13.1, an error shall be flagged.

%prefix isbn urn:isbn:

isbn:3-7026-4850-X isa book
- "Das kleine Ich bin Ich"
        

3.3.5 IRI References

IRI references are either QNames or IRIs. They are interchangeable: Everywhere an IRI can be used a QName can also be used (provided the prefix is defined at that point).

3.3.6 Topic References

Topics are referenced by an item identifier, a subject identifier, or a subject locator.

During deserialization, one topic item is created for each topic-ref.

If the topic-ref is an identifier and a default prefix has been declared, an IRI is created by concatenating the default prefix and the value of the identifier. The locator is added to the [subject identifiers] property of the topic.

If the topic-ref is an identifier and no default prefix has been declared, a locator is created by concatenating the document IRI, a # character, and the value of the identifier. The locator is added to the [item identifiers] property of the topic.

If the topic-ref is specified by a subject identifier, a locator is created and added to the [subject identifiers] property of the topic.

If the topic-ref is specified by a subject locator, a locator is created (the leading = is not part of the locator) and added to the [subject locators] property of the topic.

If the topic-ref is specified by an item identifier, a locator is created (the leading ' is not part of the locator) and added to the [item identifier] property of the topic.

If the topic-ref is specified by a wildcard, a locator is created. The locator shall use the document locator as base with a concatenated # and a random identifier. That locator shall not be equal to any other subject identifier, subject locator or item identifier contained in the topic map. The unique, newly created locator is added to the [item identifiers] property of the topic. This operation shall not cause any merging operation.

If the topic-ref is specified by a named-wildcard, at the first occurrence of such construct a unique locator is created which shall use the document locator concatenated with # and a random identifier such that the result is unique in the topic map. This locator is added to the [item identifiers] property of the newly created topic. This operation shall not cause any merging operation. If the named-wildcard is used again, the same topic is reused. No whitespaces are allowed between the ? and the identifier.

If the topic item created through deserialization of a topic-reference is equal to another topic item (c.f. [TMDM] 5.3); the two topic items are merged according to the procedure given in [TMDM].

# A topic referenced by the subject locator "http://www.isotopicmaps.org/"
= http://www.isotopicmaps.org/

# A topic referenced by a subject identifier
http://psi.example.org/John_Lennon

# A topic with a unique, randomly created item identifier. Within the CTM
# document it is not possible to reference this topic by item identifier.
? - "A topic"

# A topic with a unique, randomly created item identifier which may be
# referenced again within the CTM document.
?foo - "A new, unique topic"

# Another reference to the same topic later in the document
?foo isa subject

3.3.7 Scope

The scope construct is used to assign a scope to an information item.

During deserialization, each topic-ref element is processed according to the procedure described in 3.3.6. These topic items are gathered into a set that is assigned as the value of the [scope] property of the Topic Maps construct being processed.

3.3.8 Reifier

The reifier construct is used to refer from the Topic Maps construct on which it appears to the topic reifying that construct. The reference is a topic-ref as described in 3.3.6

During deserialization the topic-ref is resolved into a topic item following the procedure in 3.3.6. The topic item is set as the value of the [reifier] property of the Topic Maps construct being processed.

3.3.9 Type

The type construct is used to assign a type to the Topic Maps construct in which it occurs. The type is always a topic, indicated by the topic-ref.

During deserialization the topic-ref produces a topic item following the procedure in 3.3.6, which is set as the value of the [type] property of the information item being processed.

3.4 Literals

A literal is a string value with an optional datatype.

For convenience, this part of ISO/IEC13250 support native identification of integers, decimals, IRIs, dates and dateTime values.

The following implicit datatypes are associated with the above mentioned literals:

iri-ref

http://www.w3.org/2001/XMLSchema#anyURI

If the iri-ref is a QName, the QName converted into an IRI by the procedure described in 3.3.4.

decimal

http://www.w3.org/2001/XMLSchema#decimal

integer

http://www.w3.org/2001/XMLSchema#integer

undef

http://www.topicmaps.org/ctm/undef

date

http://www.w3.org/2001/XMLSchema#date

date-time

http://www.w3.org/2001/XMLSchema#dateTime

string

http://www.w3.org/2001/XMLSchema#string

Any literal can be expressed by representing the value as a string and appending the datatype qualifier (^^) and a iri-ref which indicates the datatype.

If the literal occurs inside an occurrence (3.8), the occurrence [value] property is set to the value of the literal and the occurrence [datatype] property is set to the datatype of the literal.

If the literal occurs inside a variant (3.10), the variant [value] property is set to the value of the literal and the variant [datatype] property is set to the datatype of the literal.

42  # equivalent to "42"^^xs:integer

"09-19"^^xs:gMonthDay

3.4.1 String Escape Sequences

String escape sequences can be used to either escape characters which have special meaning in the grammar (i.e. ") or to enter characters which are not available on the keyboard by providing their Unicode codepoint.

3.5 Topic Map

The topicmap component acts as a container for the topic map but has no further significance. It is declared as follows:

3.5.1 Prolog

The prolog occurs at the start of the CTM document and consists of an (optional) encoding directive and an (optional) version directive.

3.5.2 Encoding Directive

The encoding directive specifies the character encoding used by the document.

If the encoding declaration is omitted, UTF-8 encoding is assumed. The name of the encoding shall be given as a string in the form recommended by [XML 1.0].

If the encoding is provided, it shall occur in the first line of the document.

%encoding "Shift-JIS"

3.5.3 Version Directive

The version directive states the version number of the CTM syntax, which is currently "1.0". It is declared as follows:

The version directive tells the parser which version of the CTM syntax to use during deserialization. Currently the only legal version is 1.0, as defined by this part of ISO/IEC13250.

While the version directive may be omitted, this part of ISO/IEC13250 recommends its usage for future compatibility.

If the version directive is provided, it shall occur after the encoding directive on the second line of the document. If the encoding directive is omitted, the version directive shall occur on the first line of the document.

%version 1.0

3.5.4 Topic Map Reifier

During deserialization the topic is resolved following the procedure in 3.6 and the topic item is set as the value of the [reifier] property of the topic map.

# Fragment A
~ tm-reifier - "My topic map"

# Fragment B
~ tm-reifier

tm-reifier
- "My topic map"

3.6 Topics

The topic construct is used to declare a topic, assign identifiers to it, and make statements about it, through the assignment of names and occurrences, or the invocation of templates which generate associations (and/or additional names and occurrences). It starts with a topic reference and ends with either a blank line or a period.

During deserialization a topic item is produced and given an identifier by processing the topic-ref in accordance with the procedure described in 3.3.6.

If additional subject identifiers or subject locators are specified, an IRI is created for each of them according to the procedure described in 3.3.6 and added to the [subject identifiers] or [subject locators] property of the topic respectively.

If either of these procedures makes the topic equal to another topic item (c.f. [TMDM] 5.3); the two topic items are merged according to the procedure given in [TMDM].

If the topic construct contains template invocations (3.12), the first argument is automatically bound to the topic item produced by the procedures above.

The instance-of production creates a type-instance relationship according to [TMDM] 7.2 where the topic on the right hand side plays the role http://psi.topicmaps.org/iso13250/model/type and topic produced by the procedures above plays the role http://psi.topicmaps.org/iso13250/model/instance.

The kind-of production establishes a supertype-subtype relationship according to [TMDM] 7.3 where the topic produced by the the procedures above plays the role http://psi.topicmaps.org/iso13250/model/subtype and the topic on the right hand side plays the role http://psi.topicmaps.org/iso13250/model/supertype.

john-lennon    # a topic with an item identifier and nothing else

lennon . mccartney . harrison . starr . # four topics on one line

# A topic defined by its subject locator
= http://www.isotopicmaps.org/
  - "The ISO Topic Maps Web Site"

# A topic defined by a subject identifier
http://psi.example.org/John_Lennon
  - "John Lennon"

# A topic with a local identifier and a subject identifier
john http://psi.example.org/John_Lennon
  - "John Lennon"

3.7 Associations

The association construct is used to add associations to the topic map. It is declared as follows:

During deserialization an association item is created for each association and added to the [associations] property of the topic map item. The [type] property of the association is set to the topic produced by the assoc-type.

During deserialization an association role item is created for each role. The role item is added to the [roles] property of the association item.

member_of(group: The_Beatles, member: John_Lennon)

3.8 Occurrences

The occurrence construct is used to add occurrences to a topic. It is declared as follows:

During deserialization the occurrence construct causes an occurrence item to be created, and added to the [occurrences] property of the topic item created by the procedure decribed in 3.6.

Paul_McCartney
  birthday: 1942-02-18
  webpage:  http://en.wikipedia.org/wiki/Paul_McCartney

3.9 Names

The name construct is used to add a topic name to a topic. It is declared as follows:

During deserialization the name construct causes a topic name item to be created, and added to the [topic names] property of the topic item created by the procedure decribed in 3.6.

If the type is not specified, the [type] property of the topic name item is set to the topic item whose [subject identifiers] property contains http://psi.topicmaps.org/iso13250/model/topic-name; if no such topic item exists, one is created.

john-lennon
  - "John Lennon"                      # Name with the default name type
  - fullname: "John Winston Lennon"    # Name of type 'fullname'

3.10 Variants

The variant construct is used to add a variant name to a topic name. It is declared as follows:

During deserialization the variant construct causes a variant item to be created and added to the [variants] property of the topic name item created by the procedure described in 3.9. After the scope has been processed, the topics in the [scope] property of the topic name item created by the parent name construct are added to the [scope] property of the variant name item.

%prefix tm http://psi.topicmaps.org/iso13250/model/
# a topic with a sort name variant
john
  - "John Lennon" ("lennon, john" @ tm:sort)

3.11 Templates

Templates are containers for arbitrary Topic Maps constructs and certain CTM directives. The template body consists of ordinary topics and associations and allows topic references (3.3.6) and literals (3.4) to be replaced by variables. They are defined as follows:

In the template-body variables are allowed wherever topic-refs or literals are allowed.

The declaration of a template does not change the topic map content until the template has been invoked by a template-invocation (3.12).

If a template with the same identifier has already been defined, an error is flagged.

# Declaration of a template that sets the topic type to 'person', creates an
# occurrence of type 'birthday', and creates an association of type 'born-in'
def born($person, $date, $place)
    $person isa person
    birthday: $date .
    born-in(person : $person, birthplace : $place)
end

# Invocation of the template inside a topic block
mccartney
  born(1942-06-12, Liverpool)

# Invocation of the template outside topic block
born(mccartney, 1942-06-12, Liverpool)

# Both of the above have the same effect as the following
mccartney
  isa person
  birthday: 1942-06-12 .
born-in(person: mccartney, birthplace: Liverpool)

If a template contains a prefix directive (3.13.1), the prefix is only valid within the template body. Prefixes previously declared outside the template are accessible within the template body.

If a named-wildcard is used inside the template body, it is accessible only within the template. A named-wildcard causes the creation of a topic each time the template is invoked.

Template names and topic identifiers do not share the same namespace. If a template with name A exists, it is still possible to declare a topic with the identifier A.

3.12 Template Invocation

A template invocation causes the statements of the template to be added to the topic map with the variables in the statements replaced by the specified arguments.

If the template was not previously defined, an error is flagged.

If the template-reference is a qname and the prefix was not created by the procedure described in 3.13.4, an error is flagged.

If any variables are not bound, an error is flagged.

# Template invocation within a topic declaration
mccartney
  plays-for(The_Beatles, piano)
  has-shoesize(42)

# Template invocation outside of topic declarations
plays-for(john, The_Beatles, guitar)
has-shoesize(john, 45)

def wiki-entry($iri, $name)
  $iri                # Used as subject identifier
  - $name
  description: $iri . # Used as occurrence value
end

wiki-entry(<http://en.wikipedia.org/wiki/John_Lennon>, "John Lennon")


# The following template invocation fails, because a subject locator is
# provided which cannot be used as value of an occurrence.

wiki-entry(=<http://en.wikipedia.org/wiki/Paul_McCartney>, "Sir Paul McCartney")  # -> Error!

def is-beatle($beatle)
  is-member-of($beatle, The-Beatles)
end

def is-member-of($member, $group)
  member-of(member: $member, group: $group)
end

is-member-of(sting, The-Police) # Invoking the 'raw' is-member-of template

is-beatle(john)

3.13 Directives

Directives are used to define the environment for a CTM processor. Each directive shall occur in a line of its own. Only a comment is allowed on the same line.

3.13.1 Prefix Directive

The prefix directive is used to associate an IRI with an identifier. It is declared as follows:

During deserialization the prefix component binds the identifier to the IRI.

If the identifier is already bound, an error is flagged unless the identifier is bound to one and the same reference.

An error shall be flagged if the concatenation of the iri and the local part of a QName does not produce a valid IRI.

%prefix wiki http://en.wikipedia.org/wiki/

wiki:John_Lennon                   # QName used as a subject identifier
  description: wiki:John_Lennon    # QName used as the value of an occurrence

If no identifier is specified, the reference becomes the default prefix.

# prefix directive with no identifier
%prefix http://psi.example.com/

# Topic with the subject identifier http://psi.example.com/John_Lennon
John_Lennon
  - "John Lennon"

3.13.2 Include Directive

The include directive is used to include another CTM document into the CTM file. The other document is referenced by an IRI.

The referenced document shall use CTM syntax, otherwise an error is flagged.

During deserialization the include component causes the referenced topic map to be immediately deserialized into a data model instance. The new data model instance (B) is then merged into the current one (A) by

• Iterating through all topic item in B's [topics] property and identifying those topics which contain a locator in their [item identifiers] property which starts with the referenced document locator.

  For each of the identified topics a locator is created by subtracting the referenced document locator from the item identifier which start with the referenced document locator.

  The result of that subtraction is concatenated with the document locator of A. The result is an absolute locator which is added to the [item identifiers] property of the topic.

• Adding all topic items in B's [topics] property to A's [topics] property.

• Adding all association items in B's [associations] property to A's [associations] property.

3.13.3 Mergemap Directive

The mergemap directive is used to merge an external topic map into the topic map produced by deserializing the CTM topic map.

This directive is declared as follows:

The topic map to be merged can be in any syntax, which shall be declared (using the notation component) if it is not CTM.

This part of ISO/IEC13250 uses the following identifiers for Topic Maps syntaxes:

CTM

http://www.topicmaps.org/ctm/

XTM

http://www.topicmaps.org/xtm/

A conforming CTM processor shall support the above mentioned syntaxes. For any other syntax a CTM processor may flag an error.

During deserialization the mergemap component causes the referenced topic map to be immediately deserialized into a data model instance. The new data model instance (B) is then merged into the current one (A) by

• Adding all topic items in B's [topics] property to A's [topics] property.

• Adding all association items in B's [associations] property to A's [associations] property.

3.13.4 Template Import Directive

The template-import directive is used to make templates from another CTM document usable in the current document.

The identifier causes a prefix to be created, after which the templates can be invoked with the QName notation (identifier:template-name). If the prefix is already in use, an error is flagged.

The referenced document shall contain directives and template definitions, only.

An error shall be flagged if the referenced document contains topics, associations, or template invocations.

%import http://example.org/my-template-lib.ctm as my-lib

mccartney my-lib:member_of(The_Beatles)
          my-lib:plays(piano)

A Syntax (informative)

Core Syntax

Bibliography

ISO/IEC 13250:2003, Topic Maps, 2003, http://www.y12.doe.gov/sgml/sc34/document/0322_files/iso13250-2nd-ed-v2.pdf

ISO 13250-4, Topic Maps — Canonicalization, http://www.isotopicmaps.org/sam/cxtm/