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CGM Open specification - WebCGM 2.0 - Appendixes


A. Acknowledgements

In addition to the listed authors of this specification, the following individuals have contributed significantly to the present WebCGM specification:

The following individuals made significant contributions to WebCGM 1.0:

A. What's new in WebCGM 2

This section is informative (non-normative).

  1. WebCGM DOM. A major functional addition is a limited WebCGM Document Object Model (DOM), carefully targeted at the WebCGM 2.0 requirements.
  2. WebCGM XCF. The second major functional addition is the definition of a standard XML Companion File for use by WebCGM (and related) applications, closely integrated with WebCGM DOM.
  3. Event model. As an adjunct to the DOM definition, a more detailed event model has been specified, allowing definition and attachment of user event handlers to objects, and specifying how "pick" events are handled in a backward compatible way to WebCGM 1.0.
  4. Complementing the event model, a new param sub-element is added to the OBJECT element, to allow handling of onload events.
  5. Single picture. Whereas ISO CGM:1999 allows multiple independent pictures in a metafile, and WebCGM 1.0 originally did, multiple pictures were deemed not amongst the requirements for WebCGM. To simplify WebCGM, they were deprecated in WebCGM 1.0 2nd Release, and are now removed from WebCGM 2.0.
  6. Fragment syntax. Small changes to allowable values, in order to embody the single-picture rule, but the overall structure of the fragment is unchanged for backward compatibility.
  7. Fragment syntax and xcfterm. It is now possible in the link fragment to specify to load-and-apply an XML companion file before first display of the graphics of a targeted picture.
  8. More object behaviors. The set of object behaviors that can be included in the link fragment syntax has been expanded to give much more user control. A set of behaviors is built from EBNF syntax, by combinations of an orthogonal navigation term and highlighting term. The 3 behaviors of WebCGM 1.0 are deprecated.
  9. Grnode. WebCGM 2.0 defines a purely graphical grouping mechanism, "graphical node", which groups graphical primitives as an Application Structure, but disallows the attributes or properties that associate intelligence with objects.
  10. New APS attributes. WebCGM defines new APS attributes of type 'visibility' and 'interactivity' that may be applied to most object (APS) types.
  11. Style Properties. For use in DOM and XCF, WebCGM 2.0 defines a set of Style Properties -- text color, stroke weight, etc -- that transiently (for the duration of a DOM or viewing session) override the corresponding CGM attributes for targeted picture and APS nodes.
  12. Obsolete features. A number of previously deprecated WebCGM 1.0 features are made obsolete (removed from WebCGM 2.0).
  13. Deprecated features. A number WebCGM 1.0 features are deprecated in WebCGM 2.0 (may be removed in a future revision).
  14. Symbol Libraries. This capability was in WebCGM 1.0, but was removed from WebCGM 2.0 because of lack of interest (POLYSYMBOL, several SYMBOL LIBRARY elements, some registered ESCAPEs, etc).
  15. 2.0 and has added some graphical items that were deferred from WebCGM 1.0 (for expedience)

B. Glossary

API, Application Programming Interface
An Application Programming Interface (API) is a set of functions or methods used to access some functionality.
Application Structure, APS
The CGM structure for grouping other elements and assigning them a unique identifier, a type, and attaching attributes. WebCGM contains five valid APS types: grobject, layer, para, subpara, grnode.
APS Attribute, Application Structure Attribute
The CGM element that is used to define and associate an attribute with an APS. WebCGM contains ten valid APS Attribute types: region, viewcontext, linkuri, layername, layerdesc, screentip, name, content, visibility, interactivity.
Cascading profile
A method by which closely related profiles can be expressed efficiently, by only enumerating the differences between a given profile and a base profile such as WebCGM.
CGM, Computer Graphics Metafile
ISO/IEC standard 8632:1999 (CGM:1999), CGM is a metafile format consisting of composite raster and scalable vector graphics information.
DOM, Document Object Model
A Document Object Model is a platform- and language-neutral interface that allows programs and scripts to dynamically access and manipulate the content, structure and style of documents. WebCGM defines a DOM of limited scope, allowing discovery and navigation of the WebCGM structure tree, transient manipulation of styles and standardized metadata, and discovery and manipulation of application-specific metadata. The WebCGM DOM is based upon and borrows from the principles the W3C DOM Level 2 and DOM Level 3 Recommendations.
EBNF, Extended Bauer Normal Form
A formal specification technique used in WebCGM to express pieces of grammar and syntax such as the URI fragment syntax.
fragment (URI fragment)
As standardized in RFC 3986, the fragment is a part of a URI that is separated from the path/file name by a "#" character, and provides information that is reserved for processing by agents that are invoked by the browser to handle the resource information type of the URI. WebCGM standardizes the syntax and semantics of a URI fragment, for transmitting object and picture selection and behavior information to WebCGM viewers.
handler, event handler
An event handler is a method called by the WebCGM DOM implementation whenever a specified event occurs. Users register the event types they are interested in by calling the addEventListener() method of the WebCGMMetafile object.
host application
The user agent, typically is a script that controls the behavior of a web page. In the context of WebCGM the host application controls the behavior of the WebCGM renderer through the DOM.
host document
The web page, contains a combination of both HTML and WebCGM content.
host environment
The combination of the host application and the host document
The determination of values of APS Attributes and Style Properties for objects in the WebCGM hierarchical object tree, when all aspects have not been explicitly specified for all objects in the tree. WebCGM defines an inheritance model that is closely based on CSS (Cascading Style Sheets, a W3C Recommendation).
interactive region
the effective geometric region for the purposes of all interactive cursor and mouse operations, such as picking and mouseover. By default, the drawn graphical primitives of the object define the interactive region. For filled-area primitives this includes: the edge, if edge visibility is 'on'; the interior, if the interior style is other than 'empty' or 'hollow'; and, the boundary, for interior style 'hollow'. For all graphical primitive types, drawn graphical primitives exclude any that are fully transparent (so a fully transparent object is equivalent to an empty object, for purposes of interactive region definition). If the object contains a 'region' APS Attribute, then that region area is the interactive region.
listener, event listener
The event listener specifies the interface via which users register event handlers with the WebCGM DOM implementation. This interface consists of a single method, handleEvent(), which the WebCGM DOM implementation calls whenever specified events occur. Users pass WebCGMEventListener objects as arguments to the addEventListener() method of the WebCGMMetafile object to register a specific event handler with the WebCGM DOM implementation.
Non graphical information contained within or associated with standard graphical files, in WebCGM metadata supports such ancilliary functions as hierarchical picture structuring, object identification and navigation, and association of application-specific non-graphical data with graphical objects.
A mechanism for retraining and transporting graphical data and control information, containing a device independent description of one or more pictures.
namespace, NS
A method devised and standardized by the XML Namespaces standard, namespace provides a way to distinguish to which specification and grammar elements and attributes belong, when information from distinct XML languages is mixed in the same document. WebCGM uses namespaces to separate standardized WebCGM XCF elements and attributes from embedded and intermingled application-specific metadata.
Normalized Device Coordinates, NVDC
The coordinate system that is used to communicate coordinate data through the WebCGM DOM, NVDC is VDC normalized so that the origin is lower-left and units are millimeters.
An Application Structure or Picture in a WebCGM.
object behavior
One of a set of (thirteen) ways in which the view of an object or collection of objects is presented following the execution of a hyperlink to the object(s). WebCGM standardizes a number of objects that give complete control over the zoom, pan, and highlight aspects of the view.
picture behavior
One of a set of ways in which the view of a picture (CGM) or document (HTML) is handled following the execution of a hyperlink to the content. Based on the 'target' attribute of the HTML 'a' tag, picture behaviors allow the specification of the new view to occur in a new window, to overwrite the whole contents of the source window, to overwrite the parent window, etc.
PPF, Profile Proforma
A method of expressing profiles standardized in CGM:1999 (clause 9), the PPF presents a profile as a single table covering all aspects of the CGM standard, with a reference column (enumerating a Model Profile or other base profile), and a column to define the target profile by comparison to the reference column.
Style Property
A graphical attributes that may be applied and manipulated at the APS or picture level, transiently, by WebCGM DOM and WebCGM XCF. WebCGM 2.0 defines nine style properties.
target rectangle
A rectangular region around the target object(s) that is used for the application of object behaviors following hyperlink execution. The target region is defined by APS Attributes and/or target geometry, and for example provides the area to be encompassed by a zoomed view.
The WebCGM Document Object Model, this terminology is used when it is needed to unambiguously distinguish the WebCGM DOM from the generalized W3C DOM specifications.
XCF, XML Companion File
An XML file format defined by WebCGM, that can be used to externalize metadata from WebCGM instances and bind it to objects in the metafile.

C. Change Log

This section is informative (non-normative).

Changes since OASIS-published first Committee Draft:

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