ISO/IEC JTC 1/SC34 N0393

ISO/IEC JTC 1/SC34

Information Technology --

Document Description and Processing Languages

28 March 2003

JTC 1/SC 34 N 0393

Table of Contents

Topic maps are bodies of information that consist of "topics", each of which is a surrogate for a single subject. If every topic in a topic map is the only surrogate for its subject, then users can find all information about that subject in a single location. The Topic Maps Model — the information structure of all topic maps that is defined by this International Standard — constrains the definitions of Topic Maps Applications in order to enable the achievement of this "Subject Location Uniqueness Objective [SLUO]". It specifies a foundation for lossless and uniform treatment of heterogeneous topic map information.

The Topic Maps Model meets the following requirements:

1. It enables an unbounded number of different Topic Map Applications to be created and used.

2. It enables metrics to be developed for arbitrary sets of Topic Map Applications.

3. It enables Topic Map Applications to be expressed as topic maps.

4. It enables the conformance of Topic Map Applications to this International Standard to be verified.

5. It enables rigorous specification and auditing of the process whereby an interchangeable topic map is understood as a set of subjects. It enables specification of conventions for referring to members of that set of subjects by referring to components of interchangeable topic maps.

6. It enables determination of whether two topic maps are identical.

7. It facilitates the specification and determination of subject identity by humans, as well as machines.

8. When two or more topic maps are merged automatically, the Topic Maps Model:

   1. enables the merging process to be consistent across Topic Map Applications and their implementations, and

   2. preserves the integrity of the information contained in the merged topic maps in the resulting single topic map.

The Topic Maps Model meets the above requirements by:

1. Defining the uniform structure, and the subjects which are the substantive aspects, of all relationships between subjects, and by defining, naming, and constraining the properties that reflect that structure.

2. Requiring TM Applications to define explicitly the properties of topics that are required to determine the identities of their subjects, the rules for assigning values to them, and the rules for comparing them.

This International Standard specifies:

1. the information structure of all topic maps;

2. certain common properties of topics, and constraints on the values of those properties;

3. constraints on the definitions of Topic Map Applications;

4. the definition of the term "fully merged" as it applies to topic maps; and

5. other definitions and specifications that support the foregoing.

An "assertion" topic. The subject of an a-topic is the relationship that is represented by an assertion; an a-topic is the nexus of a specific assertion.

A statement of a relationship between subjects, each of which is a called a "role player" in the relationship. An assertion represents a relationship as a specific set of topics that collectively connect the topics (x-topics) whose subjects are the role players to an "a-topic" whose subject is the relationship itself. Every assertion also includes topics whose subjects are: (i) the type of the relationship (the t-topic), if any, (ii) for each role, the fact that a role player is "cast" in the role in the relationship (the c-topics), and (iii) the roles themselves (r-topics). Within any given assertion, the a-topic, the t-topic (if any), the c-topics, the r-topics, and the x-topics directly or indirectly have each other as the values of their TMM-defined OPs.

As in "built-in property instance value [component]": required by a TM Application Definition and/or Syntax Deserialization Definition to be assigned to a property instance regardless of the situation of the topic. "Built-in" is the opposite of "conferred".

In an assertion, a topic whose subject is one of the castings of the assertion.

The fact that a subject plays a specific role in a relationship; the subject of a c-topic.

As in "conferred property instance value [component]": required by a TM Application Definition and/or Syntax Deserialization Definition to be assigned to a property instance on account of the situation of the topic. "Conferred" is the opposite of "built-in".

The condition of a topic map in which every subject is represented by only one topic. See 9.

Pertaining to the components of a single assertion instance.

1. The process whereby two topics become a single topic, on account of the fact that they are deemed to have the same subject, in the service of the Subject Location Uniqueness Objective. See 9.5.

2. The process whereby a topic map in which more than one topic has the same subject becomes a "fully merged" topic map, in which every reified subject is reified by only one topic. See 9.

Other Property.

A property class or property instance that is not a Subject Identity Discrimination Property (SIDP).

1. A property class.

2. A property instance.

A class of name/value pairs defined by either the Topic Maps Model ("TMM-defined") or by a TM Application ("TMA-defined") as being instantiable as components of topics.

A uniquely named component of a topic; a name/value pair that is an instance of a property class. It may be either built-in or conferred.

A "role" topic. The subject of an r-topic is a role in a relationship and/or relationship type.

Represented by a surrogate. (Topics reify subjects.)

A role in a relationship.

1. A subject that plays a role in a relationship.

2. An x-topic.

Syntax Deserialization Definition.

Subject Identity Discrimination Property.

Subject Location Uniqueness Objective

A topic's status as an a-topic, c-topic, r-topic, t-topic, and/or x-topic in one or more assertions, and the status of each of the topics whose subjects are aspects of those assertions, recursively.

A path from a situated topic to one of the topics in its situation that has defined characteristics that trigger the conferring of a value or value component on one of its properties.

Any thing whatsoever, regardless of whether it exists or has any other specific characteristics, about which anything whatsoever may be asserted by any means whatsoever.

1. A property instance which specifies the subject of the topic of which it is a component, and which independently serves as the only basis for any applicable merging rule(s). The opposite of Other Property (OP).

2. A property class designed so that each instance independently and comprehensively specifies the subject of a topic, and in terms of which any applicable merging rules are defined. The opposite of Other Property (OP).

The objective of the topic map paradigm, which is to enable everything that is known about a subject to be accessible from one place.

A definition of the mapping process whereby each kind of construct found in instances of a specific syntax must, when encountered, deterministically result in the addition of topics with certain property values to the topic map that the syntactic instance is intended to represent.

Topic Map Application

The definition of a TM Application.

Topic Map Application

Defined by a Topic Map Application (the opposite of TMM-defined).

Defined for all topic maps by this Topic Maps Model (TMM) in 4.2, regardless of their governing TM Applications (the opposite of TMA-defined).

A non-empty set of property instances that serves as a surrogate of a subject.

A construct in an instance of an interchangeable topic map which can be referenced as a way of referencing the topic to which, by convention, it corresponds in the deserialized topic map that the interchangeable topic map is intended to represent.

A body of information consisting of a non-empty set of topics.

A defined set of assertion types, properties, merging rules, and their supporting definitions that is intended to govern the expression and merging behaviors of a set of topic maps. It is not a "software application"; it is a world view, expressed in a way that enables it to be implemented uniformly.

This International Standard.

Regarded (as a list) in such a way as to ignore both the order of the items in the list, and any duplicates that appear in the list.

When the values of two property instances of the same property class include lists that are required to be treated as sets, their equality or inequality can be determined by any procedure that yields the same results as the following procedure:

1. Make each item in each list unique in that list, i.e., delete all duplicate items from each list.

2. Apply the same comprehensively deterministic order-normalization algorithm to both lists.

3. Compare each item in one list for identity with the item in the corresponding position in the other list.

If all the pairs of items in corresponding positions in the two lists are identical, the two sets are equal. If any pair of corresponding items are not identical to each other, or if the lengths of the two lists are not the same, the two sets are not equal.

A distinct portion of a single property value, such as a member of a complex value or a member of set.

In a topic map, all subjects that are defined, and/or about which any information is conveyed, are represented by topics. The number of topics in a topic map is finite; in order to create a topic map it is necessary to choose the subjects that will be represented in it.

Topics consist of property instances. Each is an instance of a property class. A single topic can be comprised of properties defined by multiple TM Applications. In a topic, no two properties can be instances of the same class (can have the same name).

Some properties are Subject Identity Discrimination Properties (SIDPs). All others are called "Other Properties (OPs)".

Some property instances are "built-in". All others are "conferred".

Some properties are "TMM-defined". All other properties are "TMA-defined".

Every property has a name; the name is different from that assigned to all other properties, assertion types, and roles.

Property instances exist only if values have been assigned to them.

The definitions of property classes specify the types of the values of their instances. The value type of a property may be simple (without substructure) or complex (having substructure nested within it). The values may be or include lists and lists treated as sets.

Every topic has at least one SIDP instance. Each SIDP instance independently specifies the subject of the topic, for all purposes of subject identification. SIDP values are the only basis for automatically recognizing when two topics have the same subject or different subjects, and should therefore either be merged or left unmerged. No topic can have more than one SIDP instance whose property class is defined by any single TM Application.

The values of OPs do not influence the automated merging process defined by the Topic Maps Model.

Subjects have relationships with each other. These relationships are themselves subjects, and they have substantive aspects which are also subjects.

When a topic represents a relationship among subjects, such a topic is called an "assertion topic" or "a-topic". Every a-topic is the nexus of a set of topics, called an "assertion". Each member of the set (including the a-topic) represents a subject which is a substantive aspect of the relationship.

An a-topic cannot also be a c-topic, r-topic, or t-topic; the subjects of a-, c-, r-, and t- topics are all mutually exclusive (no topic can have more than one subject).

When a relationship exists among subjects, each subject so related is called a "role player". In the context of any specific assertion, each topic that represents a role player in that assertion is called an "x-topic".

All subjects, without exception, are eligible to be role players in relationships; therefore all topics are eligible to be x-topics, regardless of whether or not they are a-topics, t-topics, r-topics, c-topics.

Each role player plays a specific role in the relationship, and each such specific role is itself a subject. In the context of any specific assertion or assertion type, each topic that represents a role is called an "r-topic".

The fact that a specific role player (or the fact that no role player) plays a specific role in a specific relationship is called a "casting". Topics whose subjects are castings are called "c-topics".

Within a single assertion, no two castings can cast role players in the same role.

When a relationship has been classified explicitly as an instance of a specific type of relationship, the type is itself a subject. Such a subject, which may be called a "relationship type" or an "assertion type", must be defined in such a way as to specify the roles and the significance (semantics) of all instances of the type. Assertion type definitions (relationship type definitions) may also specify the qualifications that should be met by the players of the roles. Topics whose subjects are assertion types are called "t-topics".

The topics in the set of topics that comprise an assertion refer to each other by means of certain of their properties. These properties, called "TMM-defined properties", are the only properties defined for all topic maps by the Topic Maps Model. (All other properties are "TMA-defined properties".) The behavior of implementations must not be inconsistent with the assertion structure and the rules for merging assertions, as that structure and those merging rules are expressed in this International Standard in terms of the TMM-defined properties.

The value is a composite that comprehensively specifies the relationship that is subject of the a-topic, in order to support the automatic determination of whether the subject is the same as, or different from, the subject of any other a-topic, in accordance with the Topic Maps Model's merging rule for a-topics.

The values of the components of the IS13250::a-sidp property (IS13250::a-sidp.t and IS13250::a-sidp.castingPairs{ }) must meet the constraints specified for them (see 4.2.2.2 and 4.2.2.3).

Any topic that has an IS13250::a-sidp property is regarded as an a-topic.

Every a-topic:

1. must have all of the TMM-defined properties whose names begin with IS13250::a-.

2. must not have any properties whose names begin with IS13250::c-, IS13250::r-, or IS13250::t-.

3. must not have any TMM-defined or TMA-defined SIDPs other than IS13250::a-sidp.

The value must be the same as the value of the IS13250::a-type property of the same topic (see 4.2.2.7).

The value is a set of pairs of topics. Each pair must uniquely correspond to one of the castings of the assertion of which the a-topic is the nexus; each pair consists of the r-topic and x-topic (if any) of the casting to which the pair corresponds. The number of pairs must be the same as the number of members in the set of c-topics that constitute the value of the a-castings{ } property.

The values of the components of each member pair (IS13250::a-sidp.castingPairs{?}.r and IS13250::a-sidp.castingPairs{?}.x) must meet the constraints specified for them (see 4.2.2.4 and 4.2.2.5).

The value must be the same as the value of the IS13250::c-role property of the c-topic whose subject is the casting to which the pair uniquely corresponds.

The value must be the same as the value of the IS13250::c-rolePlayer property of the c-topic whose subject is the casting to which the pair uniquely corresponds.

The value is the set of two or more c-topics whose subjects are the castings of the assertion of which the a-topic is the nexus.

Each of the c-topics in the value must uniquely correspond to one of the pairs in the value of the IS13250::a-sidp.castingPairs{ } property component (see 4.2.2.3.1, 4.2.2.4 and 4.2.2.5).

Each of the c-topics in the value of the IS13250::a-castings{ } property:

1. must have, as the value of its IS13250::c-role property, an r-topic that is included in the value of the IS13250::a-roles{ } property of the a-topic.