Many documents, both historical and contemporary, include not only text,
but also graphics, artwork, and other images. Although some types of images
can be represented directly with markup, it is more common practice to
include such information by using a reference to an external entity
(typically a URL) encoded in a suitable graphical notation.
In addition to graphic images, documents often contain material presented
in graphical or tabular format. In such materials, details of layout and
presentation may also be of comparatively greater significance or complexity
than they are for running text. Indeed, it may often be difficult to make a
clear distinction between details relating purely to the rendition of
information and those relating to the information itself.
Documents may also contain mathematical formulæ or expressions in other
formulaic notations, for which no notation is defined in these
Guidelines.
Finally, documents may contain musical notation, embedded in a manner
similar to tables, graphs, and formulæ.
These areas (graphics, tabular material, and mathematical or other formulæ,
and music) have in common that they have received considerable attention
from many other standards bodies or similar professional groups. In part
because of this, they may frequently be most conveniently encoded and
processed using some notation not defined by these Guidelines. For these
reasons, and others, we consider tables, formulæ, graphics, and notated music
together in this chapter.
As with text markup in general, many incompatible formats have been
proposed for the representation of graphics, formulæ, and tables in
electronic form. Unfortunately, no single format as effective as XML in the
domain of text has yet emerged for their interchange, to some extent because
of the difficulty of representing the information these data formats convey
independently of the way it is rendered.
The module defined by this chapter defines special purpose
container elements that can be used to encapsulate
occurrences of such data within a TEI-conformant document in a portable way.
Specific recommendations for the encoding of tables are provided in section
, recommendations for mathematical or other formulæ
in section , and for the encoding of musical notation
in section . Specific recommendations for the encoding
of graphic figures may be found in section . The rest
of the chapter is devoted to general problems of encoding graphic
information.
There is at the time of writing no consensus on formats for graphical
images, and such formats vary in many ways. We therefore provide (in section
) a brief discussion of the ways in which images
may be represented, and (in section ) a list of
formal names for those representations most popular at this time. Each one
includes a very brief description. These Guidelines recommend a few
particular representations as being the most widely supported and
understood.
Tables
A table is the least graphic of the elements
discussed in this chapter. Almost any text structure can be presented as a
series of rows and columns: one might, for example, choose to show a
glossary or other form of list in tabular form, without necessarily
regarding it as a table. In such cases, the global rend
attribute is an appropriate way of indicating that some element is being
presented in tabular format; similarly, the global style attribute coud be used
to provide an appropriate display property in CSS. When tabular presentation is regarded as of less
intrinsic importance, it is correspondingly simpler to encode descriptive
or functional information about the contents of the table, for example to
identify one cell as containing a name and another as containing a date,
though the two methods may be combined.
When, however, particular elements are required to encode the tabular
arrangement itself, then one or other of the various table
schemas now available may be preferable. The schemas in
common use generally view a table as a special text element, made up of
row elements, themselves composed of
cells.
Table cells generally appear in row-major order, with the first row from
left to right, then the second row, and so on. Details of appearance such
as column widths, border lines, and alignment are generally encoded by
numerous attributes. Beyond this, however, such schemas differ greatly.
This section begins by describing a table schema of this kind; a brief
summary of some other widely available table schemas is also provided in
section .
TEI Tables
For encoding tables of low to moderate complexity, these Guidelines
provide the following special purpose elements:
The table element is defined as a member of the class model.inter; it may therefore appear both within
other components (such as paragraphs), or between them, provided that
the module defined in this chapter has been enabled, as described at the
beginning of this chapter.
It is to a large extent arbitrary whether a table should be regarded as
a series of rows or as a series of columns. For compatibility with
currently available systems, however, these Guidelines require a
row-by-row description of a table. It is also possible to describe a
table simply as a series of cells; this may be useful for tabular
material which is not presented as a simple matrix.
The attributes rows and cols may be used to
indicate the size of a table, or to indicate that a particular cell or
row of a table spans more than one row or column. For both tables and
cells, rows and columns are always given in top-to-bottom, left-to-right
order, although formatting properties such as those provided by CSS may
be used to specify that they should be displayed differently. These
Guidelines do not require that the size of a table be specified; for
most formatting and many other applications, it will be necessary to
process the whole table in two passes in any case.
Where cells span more than one column or row, the encoder must
determine whether this is a purely presentational effect (in which case
the rend attribute may be more appropriate), whether the part
of the table affected would be better treated as a nested table, or
whether to use the spanning attributes listed above.
The role attribute may be used to categorize a single cell,
or set a default for all the cells in a given row. The present
Guidelines distinguish the roles of label and
data only, but the encoder may define other roles, such
as derived, numeric, etc., as appropriate.
These three attributes are provided by the attribute class
att.tableDecoration of which both
cell and row are members; see further .
The following simple example demonstrates how the data presented as a
labelled list in section might be represented by
an encoder wishing to preserve its original appearance as a table:
Report of the conduct and progress of Ernest
Pontifex. Upper Vth form — half term ending Midsummer 1851
ClassicsIdle listless and unimprovingMathematicsdittoDivinitydittoConduct in houseOrderlyGeneral conductNot satisfactory, on account of his great unpunctuality and
inattention to duties
Note that this encoding makes no attempt to represent the full
significance of the ditto cells above; these might be regarded as
simple links between the cells containing them and that to which they
refer, or as virtual copies of it. For ways of representing either
interpretation, see chapter .
The following example demonstrates how a simple statistical table may
be represented using this scheme:
Poor Man's Lodgings in Norfolk (Mayhew, 1843)
Dossing Cribs or Lodging HousesBedsNeedys or Nightly LodgersBury St Edmund's58128Thetford3636Attleboro'3520Wymondham11122
Note the use of a blank cell in the first row to ensure that the column
labels are correctly aligned with the data. Again, this encoding does
not explicitly represent the alignment between column and row labels and
the data to which they apply. Where the primary emphasis of an encoding
is on the semantic content of a table, a more explicit mechanism for the
representation of structured information such as that provided by the
feature structure mechanism described in chapter may
be preferred. Alternatively, the general purpose linkage and alignment
mechanisms described in chapter may also be applied
to individual cells of a table.
The content of a table cell need not be simply character data. It may
also contain any sequence of the phrase-level elements described in
chapter , thus allowing for the encoding of
potentially more useful semantic information, as in the following
example, where the fact that one cell contains a number and the other
contains a place name has been explicitly recorded:
US State populations, 1990
Wyoming453,588Alaska550,043Montana799,065Rhode Island1,003,464
The use of semantically marked elements within a cell enables
the encoder to convey something about the nature and significance of the
information, rather than merely suggesting how to display it in rows and
columns.
Alternatively, the role attribute might be used to convey
such information:
US State populations, 1990
Wyoming 453,588 Alaska 550,043 Montana 799,065 Rhode Island1,003,464
The content of table elements is not limited to head and
row. Milestone elements such as cb and lb
allow new columns or lines to be signalled inside tables; figure provides an
option for including data which is not amenable to normal row and cell
analysis; and other elements such as epigraph and
trailer provide options for including text which is clearly
part of the table, but outside the actual tabular layout. This example
shows the use of trailer:
The Table of Battallions, reduced out of the grand square of
men.
12348413289 289 2567The end of the Table of Battallions reduced out of the
battels of g. and squares of men: vpon the right side of euery
leafe.
Other Table Schemas
Many authoring systems include built-in support for their own or for
public table schemas. These provide an enhanced user interface and good
formatting capabilities, but are often product-specific, despite their
use of a XML markup language.
The DTD developed by the Association of American Publishers (AAP) and
standardized in ANSI Z39.59 provided a very simple encoding for
correspondingly simple tables. This has been further developed, together
with the table DTD documented in ISO Technical Report 9537, and now
forms part of ISO 12083. The TEI table model described above has
functionality very similar to that defined by ISO 12083.
For more complex tables, the most effective publicly-available DTD is
probably that developed by the US Department of Defense CALS project.
This supports vertical and horizontal spanning and various kinds of text
rotation and justification within cells and is also directly supported
by a number of existing XML software systems.
The CALS table model is much too complex to describe fully here; for
historical background see ; for
more recent simplifications of it and current implementations see . As with
any other XML vocabulary, the XML version of the CALS model may readily
be included in a TEI schema, using the techniques described in .
The XHTML table model () is based on the HTML
table model (). Both models support arrangement of
arbitrary data into rows and columns of cells. Table rows and columns
may be grouped to convey additional structural information and may be
rendered by user agents in ways that emphasize this structure. Support
for incremental rendering of tables and for rendering on
non-visual user agents
is also available. Special elements and attributes are provided to
associate metadata with tables. They indicate the table's purpose, or
are for the benefit of people using speech or Braille-based user agents.
Tables are not recommended for use purely as a means to lay out document
content, as this leads to many accessibility problems (see further ).
Stylesheets provide a far more effective means of controlling layout and
other visual characteristics in both HTML and XML documents.
Formulæ and Mathematical Expressions
Mathematical and chemical formulæ pose problems similar to those posed by
tables in that rendition may be of great significance and hard to
disentangle from content. They also require access to a wide range of
special characters, for most of which standard entity names already exist
in the documented ISO entity sets (see further chapters and ).
Formulæ and tables are also similar in that well-researched and detailed
DTD fragments have already been developed for them independently of the
TEI. They differ in that (for mathematics at least) there also exists a
richly detailed text-based but non-XML notation which is very widely used:
this is the TeX system, and the sets of descriptive macros developed for
it such as LaTeX, AMS-TeX, and AMS-LaTeX.
The AAP and ISO standards mentioned in section
above both provide DTDs for equations as well as for tables, which now
form part of ISO 12083. The European Mathematical Trust, an organization
set up specifically to enhance research support for European
mathematicians, has also defined a general purpose mathematical DTD known
as EuroMath (), for which it provides both software and services.
Most if not all of the functionality provided by these DTDs can now be
found in the OpenMath and MathML XML-based systems briefly described
below.
As with tables, in all the XML solutions a tension exists between the
need to encode the way a formula is written (its appearance) and the need
to represent its semantics. If the object of the encoding is purely to act
as an interchange format among different formatting programs, then there
is no need to represent the mathematical meaning of an expression. If
however the object is to use the encoding as input to an algebraic
manipulation system (such as Mathematica or Maple) or a database system,
clearly simply representing superscripts and subscripts will be
inadequate.
The formula element provided by these Guidelines makes no
attempt to represent the internal structure of formulæ.
By default, a formula is assumed to contain character data which
is not validated in any way. The notation used may however be named, using
the notation attribute provided by the
att.notated class.
$e=mc^2$
The character data must still be well-formed, of course, which means that
< and & must be
escaped with entity references or numeric character references, e.g.
$\matrix{0 &
1\cr<0&>1}$
Alternatively, if more detailed markup is desired, the content of the formula element may be redefined
to include elements defined by some other XML vocabulary, such as that of ISO
12083, or to use elements from the OpenMath or
MathML
schemas.
When the content of a formula element is not expressed in XML
the notation used should always be specified using the notation
attribute as above, and in the following longer example:
Achilles runs ten times faster than the tortoise and gives the
animal a headstart of ten meters. Achilles runs those ten meters, the
tortoise one; Achilles runs that meter, the tortoise runs a decimeter;
Achilles runs that decimeter, the tortoise runs a centimeter; Achilles
runs that centimeter, the tortoise, a millimeter; Fleet-footed
Achilles, the millimeter, the tortoise, a tenth of a millimeter, and
so on to infinity, without the tortoise ever being overtaken. . . Such
is the customary version. The problem does not change, as
you can see; but I would like to know the name of the poet who
provided it with a hero and a tortoise. To those magical competitors
and to the series $$ {1 \over 10} + {1 \over
100} + {1 \over 1000} + {1 \over 10,\!000} + \dots $$ the
argument owes its fame.
The notation attribute supplies the name of a notation
(TeX), which is expected to be identified somewhere in document
metadata.
Mathematical Markup Language (MathML) () is a
vocabulary for describing mathematical notation, capturing both its
structure and content.
It provides two types of markup: Presentation Markup, which captures the
notational structure of an expression and could be seen as the
TeX for the Web and Content Markup, which captures
the mathematical structure of an expression. Most of its content
elements correspond with the range of operators, relations, and named
functions typically found at the high-school level of mathematics. The
tortoise example given above in TeX can be re-expressed in MathML as
MathML 2.0 provides support for a Semantic Math-Web,
XML namespaces, and other current XML standards, such as XML DOM, OMG IDL,
ECMAScript, and Java. It also provides a modularized version of the MathML
DTD so that MathML fragments embedded in XHTML 1.1
documents can be correctly validated.
The OpenMath () project is coordinated by the OpenMath Society () and funded by the European
Commission under the Esprit Multimedia Standards Initiative that commenced
in September 1997. It is likely to become a key standard for communicating
semantically rich representations of mathematical objects both on and off
the Web in a platform-independent manner.
The OpenMath Standard () consists
of specifications for OpenMath objects, representing the structure of formulæ ();Content Dictionaries, providing semantic context ();Encodings, both binary () and XML ().
OpenMath and MathML have certain common aspects. They both use prefix
operators, both are XML-based and they both construct their objects by
applying certain rules recursively. Such similarities facilitate mapping
between the two standards. There are also some key differences between
MathML and OpenMath. OpenMath does not provide support for presentation of
mathematical objects and its scope of semantically-oriented elements is
much broader that of MathML, with the expressive power to cover virtually
all areas of computational mathematics. In fact, a particular set of
Content Dictionaries, the MathML CD Group, covers the
same areas of mathematics as the Content Markup elements of MathML
2.0.
Finally, OMDoc () is an extension of the
OpenMath standard that supplies markup for structures such as axioms,
theorems, proofs, definitions, texts (mixing formal content with
mathematical text).
In-line versus block placement for an equation can be distinguished if
desired, via the global rend attribute. The global n
and xml:id attributes may also be used to label or identify the
formula, as in the following example:
The volume of a sphere
is given by the formula: which is readily calculated.
As we have seen in equation , ...
Notated Music in Written Text
Music, like many other art forms, is often mentioned, discussed and
described in writings of various kinds. This applies to both historical
and contemporary documents, even though methods of notating music have
changed considerably in western history. In most cases, music notation
enters the text flow in a way similar to figures, images, or graphs. On
other occasions, elements of music notation are treated as inline
characters in running text.
notatedMusic provides a way to signal the presence of music
notation in text, but defer to other representations, which are not
covered by the TEI guidelines, to describe the music notation itself. In
fact several commercial, academic, and standard bodies have developed
digital representations of music notation. Given the topic's
complexity, these representations often focus on different aspects and
adopt different methodologies. Therefore, notatedMusic only
defines a container element to encode the occurrence of music notation and
allows linking to the data format preferred by the encoder. (Note:
notatedMusic is not the same as musicNotation, a
metadata element, which is used to describe musical notation that appears
in a manuscript. See .)
The following elements can be used for encoding music notation in text:
groups elements representing or
containing music notation.
can be used to indicate the location of a
representation of the music notation. mimeType supplies the MIME type of the data format,
when available.
can be used to give a prose description of
the notated music.
can be used to indicate the location of
a graphical representation of the music notation.
provides encoded binary data which
constitutes another representation of the music notation (e.g.
audio).
The notatedMusic element may contain a textual description and
pointers to various representations of the music notation in different
media. An external representation of the notated music is specified using
the ptr element, whose target attribute provides its
electronically-accessible location. The attribute mimeType
supplies the MIME type of the data format when available. For example:
A textual description of the notation can be provided within the
desc element; alternatively, a label may be supplied.
For example:
First bar of Chopin's Scherzo No.3 Op.39
It is possible to link to any kind of music notation data format.
However, when a MIME type is not available, it is recommended that the
format be specified in the description. See the following examples.
MIME type available:
First bar of Chopin's Scherzo No.3 Op.39. Encoded in
MusicXML.
MIME type not available:
First bar of Chopin's Scherzo No.3 Op.39. Encoded in
Lilypond.
Application format:
First bar of Chopin's Scherzo No.3 Op.39. MuseScore Notation
Software format.
It is possible to specify the location of digital objects representing
the notated music in other media such as images or audio-visual files. The
interpretation of the correspondence between the notated music and these
digital objects is not encoded explicitly. We recommend the use of
graphic and binaryObject mainly as a fallback
mechanism when the notated music format is not displayable by the
application using the encoding. The alignment of encoded notated music,
images carrying the notation, and audio files is a complex matter for
which we refer the reader to other formats and specifications such as MPEG-SMR.
First bar of Chopin's Scherzo No.3 Op.39
It is also recommended, when useful, to embed XML-based music notation
formats, such as the Music Encoding Initiative
format as content of notatedMusic. This must be done by means of customization.
In modern printing, music notation positioned between blocks of text for
illustrative purposes is usually referred to as a figure or
example. In this cases, we recommend the inclusion of
notatedMusic in figure in order to encode possible
captions and headers. For example:
Example from: Prout, E. (1899). The
orchestra.
We now give some examples, from the works of the great masters, of
some of the most frequently used bowings.
SCHUBERT: Symphony in B minor.
Specific Elements for Graphic Images
The following special purpose elements are used to indicate the presence
of graphic images within a document:
The graphic and binaryObject elements form part of the
common core module, and are discussed in section .
The figure element is used to contain images, captions, and
textual descriptions of the pictures. The images themselves are specified
using the graphic element, whose url attribute
provides the location of an image. For example:
Three kinds of content may be supplied inside a figure element:
the element head may be used to transcribe (or supply) a
descriptive heading or title for the graphic itself as in this example:
The View from the Bridge
Figures are often accompanied not only by a title or heading (a caption),
but by a paragraph or so of commentary (a legend) following the caption.
One or more p or ab elements
may be used to transcribe any
commentary on the figure in the source:
Above:
The drawing room of the Pullman house, the white and gold saloon
where the magnate delighted in giving receptions for several hundred
people.
The figure shows an elaborately decorated room, at least
twenty-five feet side to side and fifty feet long, with ornate
mouldings and Corinthian columns on the walls, overstuffed armchairs
and loveseats arranged in several conversational groupings, and two
large chandeliers.
Here,
the figure contains a heading Above which is complemented by a
paragraph of description The drawing room ... several hundred
people. Both of these are transcribed from the source, while the
description is provided by the encoder, for use by applications which
cannot display the graphic directly. In documents created in electronic
form with the needs of print-handicapped readers in mind, the
figDesc element may be provided by the author rather than a
subsequent encoder.
Figure One: The View from the Bridge
A Whistleresque view showing four or five sailing boats in
the foreground, and a series of buoys strung out between
them.
Where the graphic itself contains large amounts of text, perhaps with a
complex structure, and perhaps difficult to distinguish from the graphic,
the encoder should choose whether to regard the graphic as containing the
text (in which case, a nested floatingText element may be
included within the figure element) or to regard the enclosed
text as being a separate division of the text element in which
the graphic appears. In this latter case, an appropriate div or
div1 (etc.) element may be used for the text represented within
the graphic, and the figure element embedded within it. The
choice will depend to a large degree on the encoder's understanding of the
relationship between the graphic and the surrounding text.
A figure which is internally divided, or contains sub-figures, may be
encoded with nested figure elements, as in the following example.
ParallelPerspectiveThe two canonical view volumes, for the (a)
parallel and (b) perspective projections. Note that -z is to the
right.
Like any other element in the TEI scheme, figures may be given
identifiers so that they can be aligned with other elements, and linked to
or from them, as described in chapter . Some common
examples are discussed briefly here; full information is provided in that
chapter.
It is often desirable to maintain two versions of an image in an
electronic file: one a low resolution or thumbnail
version which, when selected by the user, causes the other, high
resolution, version to be accessed. In TEI terms, the thumbnail image acts
as a reference to the other. Supposing that a thumbnail
version of the figure discussed above is available as fig1th.png, we might embed a reference to the image using the
simple ref element discussed in section :
Click
here for enlightenment
Another common requirement is to associate part or the whole of an image
with a textual element not necessarily contiguous to it in the text; this
is sometimes known as a callout. When the module for
transcription is included in a schema, specific attributes for parts of a
text and parts (or all) of a digital image are available; these are
discussed in . In addition, chapter may be consulted for other mechanisms available for this
purpose.
The following example assumes that we wish to associate one portion of
the image held as fig1 with chapter two of some text, and another
portion of it with chapter three. The application may be thought of as a
hypertext browser in which the user selects from a graphic image which
part of a text to read next, but the mechanism is independent of this
particular application.
The first requirement is some way of identifying and hence pointing to
sub-parts of a graphic image. This may be done by pointing into an XML
graphic representation, for example an SVG file. Thus
These ptr elements identify two areas within the image
Fig1 by pointing at elements inside the XML file Fig1.svg, which contains the following.
The next requirement is some way of identifying the parts of the document
to which a link is to be made. The most obvious way of doing this is to
use the global xml:id attribute:
Now, all that is needed to linking these areas to the relevant chapters
is a linkGrp element, as described in section :
In this example, the SVG representation of the graphic is stored
externally to the TEI document and linked by means of a pointer. It is
also possible to embed the SVG representation directly within the TEI by
extending the content model of the figure element to permit an
element svg from the SVG namespace. Like other
customizations of the TEI scheme, this is carried out using the techniques
documented in section ; further examples are provided
in chapter .
Overview of Basic Graphics Concepts
The first major distinction in graphic representation is that between
raster graphics and vector graphics. A raster image is a list
of points, or dots. Scanners, fax machines, and other simple devices easily
produce digital raster images, and such images are therefore quite common.
A vector image, in contrast, is a list of geometrical
objects, such as lines, circles, arcs, or even cubes. These are much more
difficult to produce, and so are mainly encountered as the output of
sophisticated systems such as architectural and engineering CAD
programs.
Raster images are difficult to modify because by definition they only
encode single points: a line, for example, cannot grow or shrink as such,
since it is not identified as such. Only its component parts are
identified, and only they can be manipulated. Therefore the resolution or
dot-size of a raster image is important, which is not the case with vector
images. It is also far more difficult to convert raster images to vector
images than to perform the opposite conversion. Raster images generally
require more storage space than vector images, and a wide variety of
methods exists for compressing them; the variation in these methods leads
to corresponding variations in representations for storage and
transmission of raster images.
Motion video usually consists of a long series of raster images. Data
compression is even more effective on video than on single raster images
(mainly owing to redundancy which arises from the usual similarity of
adjacent frames). Notations for representing full-motion video are hotly
debated at this time, and any user of these Guidelines would do well to
obtain up-to-date expert advice before undertaking a project using
them.
The compression methods used with any of these image types may be
lossy or lossless. Methods for
lossy compression save space by discarding a small portion
of the image's detail, such as fine distinctions of shading. When
decompressed, therefore, such an image will be only a close approximation
of the original. In contrast, lossless compression guarantees
that the exact uncompressed image will be reproducible from the compressed
form: only truly redundant information is removed. In general, therefore,
lossless compression does not save quite so much space as lossy
compression, though it does guarantee fidelity to the original
uncompressed image.
Raster images may be characterized by their resolution,
which is the number of dots per inch used to represent the image. Doubling
the resolution will give a more precise image, but also quadruple the
storage requirement (before compression), and affect processing time for
any operations to be performed, such as displaying an image for a reader.
Motion video also has resolution in time: the number of frames to be shown
per second. Encoders should consider carefully what resolution(s) and
frame rate(s) to use for particular applications; these Guidelines express
no recommendation in this matter, save the universal ones of consistency
and documentation.
Within any image, it is typical to refer to locations via Cartesian
coordinate axes: values for x, y, and sometimes z and/or time. However,
graphic notations vary in whether coordinates count from left-to-right and
top-to-bottom, or another way. They also vary in whether coordinates are
considered real (inches, millimeters, and so on), or virtual (dots). These
Guidelines do not recommend any of these methods over another, but all
decisions made should be applied consistently, and documented in the
encodingDesc section of the TEI header.Since no special purpose element is provided for this purpose by the
current version of these Guidelines, such information should be provided
as one or more distinct paragraphs at the end of the
encodingDesc element described in section .
Methods of aligning images and text are discussed in .
The chromatic values of an image may be rendered in many different ways.
In monochrome images every displayed point is either black or white. In
grayscale images, each point is rendered in some shade of
gray, the number of shades varying from system to system. In true
polychrome images, points are rendered in different hues, again with
varying limitations affecting the number of distinct shades and the means
by which they are displayed.
Graphic Image Formats
As noted above, there exists a wide variety of different graphics
formats, and the following list is in no way exhaustive. Moreover,
inclusion of any format in this list should not be taken as indicating
endorsement by the TEI of this format or any products associated with it.
Some of the formats listed here are proprietary to a greater or lesser
extent and cannot therefore be regarded as standards in any meaningful
sense. They are however widely used by many different vendors.
The following formats are widely used at the present time, and likely to
remain supported by more than one vendor's software: BMP: Microsoft bitmap formatCGM: Computer Graphics MetafileGIF: Graphics Interchange FormatJPEG: Joint Photographic Expert GroupPBM: Portable Bit MapPCX: IBM PC raster formatPICT: Macintosh drawing formatPNG: Portable Network Graphics formatPhoto-CD: Kodak Photo Compact Disk formatQuickTime: Apple real-time image systemSMIL: Synchronized Multimedia Integration Language formatSVG: Scalable Vector Graphics formatTIFF: Tagged Image File Format
Brief descriptions of all the above are given below. Where possible,
current addresses or other contact information are shown for the
originator of each format. Many formal standards, especially those
promulgated by ISO and many related national organizations (ANSI, DIN,
BSI, and many more), are available from those national organizations.
Addresses may be found in any standard organizational directory for the
country in question.
Vector Graphic Formats
This vector graphics format is specified by an ISO standard, ISO
8632:1987, amended in 1990. It defines binary, character, and
plain-text encodings; the non-binary forms are safer for blind
interchange, especially over networks. Documentation on CGM is
available from ISO and from its member national bodies such as AFNOR,
ANSI, BSI, DIN, JIS, etc.SVG is a language for describing two-dimensional vector and mixed
vector or raster graphics in XML. It is defined by the Scalable Vector
Graphics (SVG) 1.0 Specification, W3C Recommendation, 04 September
2001, and is available at .This format is universally supported on Macintosh™ systems,
and readable by a limited range of software for other systems.
Documentation is available from Apple Computer Company, Cupertino,
California USA.
Raster Graphic Formats
PNG is a non-proprietary raster format currently widely available.
It provides an extensible file format for the lossless, portable,
well-compressed storage of raster images. Indexed-color, grayscale,
and truecolor images are supported, plus an optional alpha channel.
Sample depths range from 1 to 16 bits. It is defined by IETF RFC 2083,
March 1997.Currently the most widely supported raster image format,
especially for black and white images, TIFF is also one of the few
formats commonly supported on more than one operating system. The
drawback to TIFF is that it actually is a wrapper for several formats,
and some TIFF-supporting software does not support all variants. TIFF
files may use LZW, CCITT Group 4, or PackBits compression methods, or
may use no compression at all. Also, TIFF files may be monochrome,
grayscale, or polychromatic. All such options should be specified in
prose at the end of the encodingDesc section of the TEI
header for any document including TIFF images. TIFF is owned by Aldus
Corporation. Documentation on TIFF is available from them at Craigcook
Castle, Craigcook Road, Edinburgh EH4 3UH, Scotland, or 411 First
Avenue South, Seattle, Washington 98104 USA.Raster images are widely available in this form, which was created
by CompuServe Information Services, but has by now been implemented
for many other systems as well. Documentation on GIF is copyright by,
and is available from, CompuServe Incorporated, Graphics Technology
Department, 5000 Arlington Center Boulevard, Columbus, Ohio 43220 USA.PBM files are easy to process, eschewing all compression in favor
of transparency of file format. PBM files can, of course, be
compressed by generic file-compression tools for storage and transfer.
Public domain software exists which will convert many other formats to
and from PBM. Documentation on PBM is copyright by Jeff Poskanzer, and
is available widely on the Internet.This format is used by most IBM PC paint programs, and supports
both monochrome and polychromatic images. Documentation is available
from ZSoft Corporation, Technical Support Department, ATTN: Technical
Reference Manual, 450 Franklin Rd. Suite 100, Marietta, GA 30067 USA.This format is the standard raster format for computer using
Microsoft Windows™ or Presentation Manager™. Documentation is
available from Microsoft Corporation.
Photographic and Motion Video Formats
This standard is sponsored by CCITT and by ISO. It is ISO/IEC
Draft International Standard 10918-1, and CCITT T.81. It handles
monochrome and polychromatic images with a variety of compression
techniques. JPEG per se, like CCITT Group IV, must be encapsulated
before transmission; this can be done via TIFF, or via the JPEG File
Interchange Format (JFIF), as commonly done for Internet delivery.QuickTime is a proprietary method introduced by Apple Computer
Company to synchronize the display of various data. The data can
include frames of video, sound, lighting control mechanisms, and other
things. Viewers for QuickTime productions are available for Apple and
other computers. Further information is available from Apple Computer
Incorporated, 10201 North de Anza Boulevard MS 23AQ, Cupertino,
California 95014 USA.This format was introduced by Kodak for rasterizing photographs
and storing them on CD-ROMs (about one hundred 35mm file images fit on
one disk), for display on televisions or CD-I systems. Information on
Photo-CD is available from Kodak Limited, Research and Development,
Headstone Drive, Harrow, Middlesex HA1 4TY, UK.SMIL is a W3C Recommendation which supports the integration of
independent multimedia objects into a synchronized multimedia
presentation. It provides multimedia authors with easily-defined basic
timing relationships, fine-tuned synchronization, spatial layout,
direct inclusion of non-text and non-image media objects, hyperlink
support for time-based media, and adaptiveness to varying user and
system characteristics. SMIL 1.0 () became a W3C
Recommendation on June 15, 1998, and was further developed in SMIL
2.0. SMIL 2.0 adds native support for transitions, animation,
event-based interaction, extended layout facilities, and more
sophisticated timing and synchronization primitives to the SMIL 1.0
language. It also allows reuse of SMIL syntax and semantics in other
XML-based languages, in particular those who need to represent timing
and synchronization. For example, SMIL 2.0 components are used for
integrating timing into XHTML Document Types and into SVG. SMIL 2.0
also provides recommendations for Document Types based on SMIL 2.0
Modules (). One such Document Type is the SMIL 2.0 Language Profile (). It contains support for all of the major SMIL 2.0 features
including animation, content control, layout, linking, media object,
meta-information, structure, timing, and transition effects and is
designed for Web clients that support direct playback from SMIL 2.0
markup. SMIL 2.0 () became a
W3C Recommendation on August 7, 2001, becoming the first vocabulary to
provide XML Schema support and to have reached such status.
As noted above, the reader will encounter many, many other graphics
formats.
Module for Tables, Formulæ, Notated Music, and Graphics
The module described in this chapter provides the following features:
Tables, Formulæ, Notated Music, FiguresTables, formulæ, notated music, and figuresTableaux, formules et graphiques表格、方程式與圖表Tabelle, formule e figureTabelas, fórmulas, e figuras図表式モジュール
The selection and combination of modules to form a TEI
schema is described in .