ISO/IEC JTC1/SC18/WG8 **N849**

Title:

Statement on expanding the terms of reference of WG5 to support content
architecture development for WG8

Source:

WG8

Status of document:

WG8 approved statement

Requested action:

For consideration at SC18 Plenary

Summary of major points:

An expansion of WG5\'s scope to architectures besides ISO 8613 needs to
consider that content interfaces may be different in those
architectures.

Date

4/21/89

Distribution:

WG8 and liaisons

Approaches to content and its integration into documents

SC18\'s past experiences in dealing with differences in the treatment of
content in ODA and non-ODA document architectures can be summarized as
follows:

1\. Basic premises

a\. ODA is a document architecture. Documents conforming to this
architecture can be represented in ODIF (ASN.1) or ODL (SGML). ODA
specifies both the notations that are supported for content portions
(e.g., CGM binary, various raster notations), and the architectural
interface between the content portions and the document architecture.

b\. SGML is a document representation language. It can represent
documents that conform to standardized document architectures (e.g.,
ODA, DSSSL, and SPDL) and to non-standardized application-specific
architectures (e.g., CALS, AAP, European Patent Office, New Oxford
English Dictionary).

In SGML, the content of a document includes both subordinate elements
and \"data content\" (analogous to ODA content portions). A document
architecture can allow subordinate element content and data content of
various kinds to be intermixed at the same level, and/or to be nested
within one another.

2\. Terminology

In ISO 8879, the term \"data content\" is used to distinguish content
that does not directly contain subordinate elements. In ISO 8613, the
term \"content portions\" is used for this purpose. In order to provide
maximum alignment between the terminology of ISO 8613 and ISO 8879, the
following terms are used in this paper (the definitions are informal):

a\. content notation

The representation used for what ODA terms \"content portions\" and SGML
calls \"data content\".

b\. content notation attributes

Attributes that aid in the interpretation of a content notation without
regard to processing semantics. In ODA these are called \"coding
attributes\"; in SGML they are \"notation attributes\". Only one set of
content notation attributes should be necessary for any given content
notation. (However, a document architecture can constrain the set of
allowable values of these attributes.)

c\. content interface attributes

Attributes that relate content represented by a content notation to a
document architecture. There can be many content interfaces for a given
content notation, but normally no more than one for each document
architecture.

d\. content notation class

A set of content notations with characteristics that permit them to
share the same content notation attributes and content interface
attributes.

e\. content architecture

The combination of:

1\) a content notation (or content notation class);

2\) its content notation attributes;

3\) any constraints on the allowable values of the content notation
attributes imposed by a given document architecture; and

4\) the content interface attributes for that document architecture.

3\. Requirements of non-ODA document architectures

a\. Content notations

Standardized content notations and their corresponding notation
attributes could be beneficial. The notations should provide for
references to nested content portions of various types, and to
subordinate elements.

b\. Content interface attributes and content architectures

These must be defined by individual architectures and applications.
Attempts to standardize them outside the context of a given document
architecture would not be helpful.

A possible approach to adapting content architectures

The following is a proposed methodology for content representation
standardization to permit use by document architectures that fully
separate content architectures from document architectures.

1\. Define content notations and their notation attributes independently
of any content interface attributes.

2\. Publish the content notations as independent standards, not
associated with any document architecture standard.

3\. Aspects of a content architecture that are specific to a given
document architecture (e.g., content interface attributes) should be
developed by the Working Groups responsible for document architectures,
and published as part of the appropriate document architecture standard
(or as guidelines for developers of unstandardized document
architectures).

If this methodology were followed for the Raster Graphics Content
Architecture, for example, there would be a separate standard for
\"Raster Graphics Content Notation.\" It would contain a description of
the notation and a definition of the notation attributes, together with
their representations in ODIF and ODL. ISO 8613-8 would reference this
separate standard. It would contain the interface attributes and their
representations, together with a description of how those attributes
define the treatment of raster graphics content in the ODA processing.

WG8 offers to work jointly with WG5 to assess a methodology for adapting
its work by applying it to one or more existing content architectures.