ISO/IEC JTC 1/SC 34N0812
ISO/IEC JTC 1/SC 34
Information Technology --
Document Description and Processing Languages
|TITLE:||Draft Requirements for Graphical Topic Maps Notation|
|SOURCE:||Mr. Lars Marius Garshol|
|PROJECT:||WD 13250-7: Information technology - Topic Maps - Graphical notation|
|PROJECT EDITOR:||Prof. Jaeho Lee; Mr. Graham Moore|
|ACTION:||For information and informal comment|
|DISTRIBUTION:||SC34 and Liaisons|
Dr. James David Mason
(ISO/IEC JTC 1/SC 34 Secretariat - Standards Council of Canada)
Crane Softwrights Ltd.
Kars, ON K0A-2E0 CANADA
Telephone: +1 613 489-0999
Facsimile: +1 613 489-0995
Network: [email protected]
This is a draft requirements document for GTM, the Graphical Topic Maps Notation, which will eventually become ISO 13250-7. This draft is based on the requirements discussion at the ISO meetings in Seoul, Montréal, and Leipzig, but primarily the Leipzig meeting. As it is not yet clear if this document represents the community consensus on the requirements for GTM, feedback on this document is requested. Proposed graphical Topic Maps notations are also requested from the community.
It has been tentatively decided that GTM will consist of two sub-parts, for the time being informally known as GTM level 0 and GTM level 1. This does not imply that GTM will be a multi-part standard in the ISO sense of this term; simply that GTM will define two closely related, but different, modelling languages. (For more information, see below.)
GTM is being created to enable the communication of information by means of graphical models. However, GTM should support the communication of two different kinds of information, and so there are two different sets of purposes being served by it:
- GTM should be usable for communicating the contents of a topic map to students and readers of technical papers. This means that GTM should effectively be able to express the same information as the TMDM, but in a visual form. This is the purpose served by GTM level 0.
- GTM should be usable to communicate the constraints on a Topic Maps ontology to customers, developers, students, and readers of technical papers. This means that GTM should effectively be able to express the same information as TMCL Schema, but in a visual form. This is the purpose served by GTM level 1.
The following requirements are goals, which GTM should satisfy:
- GTM must support both of the purposes described above.
- GTM should be easy for humans to read.
- GTM should be easy for humans to write, using either
- a modelling tool with GTM support,
- a general vector drawing tool, or
- simply manually on a whiteboard or blackboard.
- GTM models should be compact, and conserve visual real estate.
- The two parts of GTM should be visually consistent; that is, they should use a common set of shapes.
- The GTM standard should not rely on colour for communicating model information. That is, if a GTM model is printed in black and white, no standardized information should be lost.
- A GTM model is not required to display every aspect of the represented TMDM/TMCL instance. If essential information is omitted, GTM must specify the shapes to be used as a "shorthand" for the omitted information. (Note that this applies only to simplifications such as omitting the type and role types of an association, and is not a general templating mechanism or support for clustering of topics.)
- The visual structure of a GTM model should correspond as closely as possible to the structure of the topic maps being either represented directly (in level 0) or constrained by the model (in level 1).
- The shapes used by GTM must be fit for purpose (e.g, something with multiple connection points should be designed in such a way as to aesthetically facilitate this).
- All GTM models must be required to use a consistent set of shapes to represent the various underlying TMCL and TMDM constructs. (That is, the shape used to represent, e.g, topic types should be consistent across all GTM models.)
- Requirements on shapes must be specified as minimal requirements only, to allow users to make extensions to GTM (such as use of colour and fill patterns) without being incompatible with the standard.
- GTM must define precisely what is considered to be consistent with the standard, and what is not. (For example, is rotation of the shape allowed; is using a fill colour inside the shape allowed, etc etc)
- GTM should aim to not constrain visual representations of GTM models any more than what is necessary for consistency. That is, the constraints on visual representations should be minimal.
- GTM must provide some way of visually representing both information from level 0 and level 1, and the connections between the two levels.
The following functionality will not be provided by GTM:
- There will be no interchange format for GTM diagrams and models similar to XMI for UML. (Except in so far as this is supported by CTM and XTM.)
- Features such as filtering, zooming, and layering will not be defined by GTM, although tools may well provide these functions, so long as the resulting models conform to GTM.
- No data model for the visual shapes will be defined.
Requirements on GTM level 0
The following are requirements on the part of GTM that is intended to represent TMDM instances:
- GTM level 0 must be able to represent all item types and properties in the TMDM.
- GTM level 0 may also define shapes for representing the type-instance and supertype-subtype association types defined by TMDM.
- There must be a precise definition of how the shapes in GTM level 0 map to constructs in the TMDM.
The following are requirements that GTM level 0 will not attempt to meet:
- GTM level 0 only represents TMDM, and no attempt will be made to represent any aspects of CTM and XTM beyond those present in TMDM.
An example of information that could be represented with GTM level 0 is: "Tosca was composed by Puccini" (an association item with two role items).
Note that since TMCL constraints have a TMDM representation it is possible to represent these constraints in GTM level 0. This is considered to be useful for communicating the TMDM representation of TMCL constraints, but not to be suitable for communicating an actual set of constraints to customers etc as described under "Purpose" above. This is why a level 1 is proposed in addition to level 0.
Requirements on GTM level 1
The following are requirements on the part of GTM that is intended to represent constraints:
- GTM level 1 must be able to express everything that TMCL Schema can express. That is, it must be possible to generate a TMCL Schema from a GTM level 1 model.
- GTM level 1 must be conceptually similar to existing modelling formalisms such as UML, ORM, and ER.
- GTM level 1 must allow a representation of TMCL constraints that is more compact than the representation of the TMDM form of these constraints in GTM level 0.
- There must be a precise definition of how the shapes in GTM level 1 map to constraints in TMCL.
An example of information that could be represented with GTM level 1 is: "every opera must have at least one composer" (a constraint on the use of the association type with the opera topic type).
The goal of the editors is to get both level 0 and level 1 into ISO 13250-7 at the same time. However, level 0 depends on TMDM, which is finished, while level 1 depends on TMCL, which is not. There is therefore a danger that level 0 could be finished before TMCL is finished. There is a general understanding that in this case, GTM will initially be published with only level 0, without waiting for level 1, and that level 1 will be added later.