Criteria fields

Criteria fields restrict the conditions under which a single translation spec will apply. If each field specified in a particular transpec matches an element under consideration in the document instance, then that translation spec is said to match. The appropriate actions, as specified in that spec, are then taken. The program, instant, searches the list of transpecs in the order given in the file. Therefore, the more restrictive specs (those with more criteria) should appear before less restrictive ones.

For quick reference, this is a brief summary of the possible criteria fields for translation. A complete discussion of each follows.

GI: gi [...]

gi is the name of the generic identifier, or element name, to consider. More than one GI may appear in this field.

AttValue: attname regular-expression

This is an attribute name-value pair, where attname is an attribute if the GI. The regular-expression is of the form accepted by the unix program egrep. This pair is compared to the corresponding attribute name-value pairs of the GI under consideration. To simply test if an attribute us set, use . (a dot) for regular-expression. There may be more than one of these lines for each transpec.

Content: regular-expression

This specifies that the character content of GI contains a string matching the regular-expression.

Context: context

This specifies the context in which to apply this translation spec. It is either a list of generic identifiers or a regular expression describing a list of generic identifiers, looking up the hierarchy. The first is the parent of the GI.

NthChild: number

This specifies that the GI is the numberth child element of its parent. Children are numbered starting with 1. Negative numbers may be used to indicate order counting backwards. For example, -1 denotes the last child.

PAttSet: attname

This specifies that the parent has this attribute, attname, set to any value (not IMPLIED). A value to match may optionally be specified after attname.

Relation: relationship gi

This specifies that the current element has the relationship to the named gi. The acceptable relationships are: ancestor (anywhere up the tree), child (immediate child), descendant (anywhere down the tree), parent (immediate ancestor), sibling (share same parent element), sibling+ (any later sibling), sibling+1 (the immediately following sibling), sibling- (any earlier sibling), sibling-1 (the immediately following sibling).

VarREValue: varname REvalue

This specifies that the global variable varname has the value REvalue, where REvalue is a regular expression (see the VarValue statement).

VarValue: varname value

This specifies that the global variable varname has the (literal) value value (see the VarREValue statement).

There are two special GIs. If specified, _Start and _End are processed as if they were GIs in the instance at the start and end of the translation, respectively. Their criteria are never checked. Only their actions are performed.

Action fields

For quick reference, this is a brief summary of the action fields for translation. They are only performed if all the criteria are satisfied. A complete discussion of each follows.

Action: spec-id

Use the actions of the spec identified by the SpecID with matching identifier spec-id.

EndText: text

This specifies text to be output when the end tag is processed.

Ignore: key

This specifies that the data or children for this element are to be ignored. Set key to all to ignore the element (data and child elements), to data to ignore the immediate character data content (child elements are still descended into), and to children to process the immediate character data content but not descended into child elements. Other actions specified in this transpec are still performed, however.

Increment: name

This is used to increment a variable whose value is a number. If the variable is not a number, no action will be taken. The variable must have been previously defined. This action is done immediately before EndText. There may be more than one of these lines for each transpec.

Message: text

This specifies a string to be printed to the standard error when the matching element is processed. It is intended for informing the user of the progress of the translation. It is also used for validation of instances (see the -v flag of instant(1)); a spec would be written to recognize a construct that is not allowed. This action is done immediately after StartText. Messages are also useful for debugging spec files; one is able to easily tell when a matching spec is processed, without looking at the actual output of the translation. Note that the spec writer is responsible for putting newlines (\n) in the message text.

Replace: text

This specifies text to replace the current subtree with. This is equivalent to StartText and Ignore.

Quit: text

This specifies text to be printed to the standard error. The program then terminates with exit status 1. This is intended for bailing out when an undesirable instance is encountered (such as when it is known that the formatting application can never handle a class of components, like tables).

Set: name value

This is used to set a variable whose name is name and value is value. Names that would be valid for GIs in the document instance are valid for variable names. value is the rest of the line and may be any string. This action is done immediately before EndText. There may be more than one of these lines for each transpec. See the discussion on variables below.

SpecID: spec-id

This names the spec with the number spec-id. Other specs may refer to this one by this number by an Action field or an _action special variable. This is used for cases where several specs to perform the exact same action.

StartText: text

This specifies text to be output when the start tag is processed.

Other Fields

These fields may appear anywhere. The action occurs when the translation spec file is read, before any elements are translated. Theses are independent of any element processing.

Var: name value

This is used to define a variable whose name is name and value is value. It is similar to Set, but it may occur anywhere in the file and takes effect when the spec file is read.

Text Strings

The text referred to in the StartText, EndText, Replace, and Message actions is more than simple character strings. Special sequences allow more complex output.

One type of special sequence is for C-style string processing. Most special characters are escaped with a \ (backslash). Like in C or shell programs, to print a \ (backslash), you must escape it with another backslash. These special character strings are:

\n (backslash-n)

This specifies that a newline character is to be printed to the output stream.

\r (backslash-r)

This specifies that a carriage return character is to be printed to the output stream.

\t (backslash-t)

This specifies that a tab character is to be printed to the output stream.

\s (backslash-s)

This specifies that a space is to be printed to the output stream. This is useful for the end of a transpec line, where it can be difficult to tell if a blank is present at the end.

\007 (backslash-007)

This specifies that the character whose octal value is 007 is to be printed to the output stream. This works for any octal character value.

^ (caret)

This specifies the that position in the string will be at the start of a line in the output stream.

If the first token of the text string is #include, then the second token is taken to be a file name and that file is included. If the file is not found, the library directory, as mentioned above, is searched. If the text string starts with a ! (exclamation point), the rest of the line is taken to be a command and the output of that command is inserted.

An element's attributes may also be used in the text of output fields. To use an attribute value, precede its name with a ${ (dollar sign-left curly bracket) and follow it with a } (right curly bracket). (This style is followed by the Bourne shell.) For example, ${TYPE}. If the attribute is not set (not IMPLIED), nothing will be printed to the output stream. To specify a value to use if the attribute is not set, place the value after the attribute name, separated by a space. To return the attribute value in lower-case, add a colon followed by lower-case l (${TYPE:l}.

Preset Variables

Several variables are preset by instant upon start of the program. Their values may be overridden in transpec files or on the command line.

date

This is the date and time that the program started. The format is: Tue 10 Aug 1993, 16:52.

host

This is the name of the host where the program is run. It is what is returned by the gethostname library call.

transpec

This is the translation spec filename.

user

This is the login name of the user running the program.

Special Variables

There is a collection of special variables called special variables. These are identified by starting the names with a _ (underscore). This is a summary of the special variables. A complete discussion of each special variable follows. spec-id refers to a number specified in a SpecID field. When used in a special variable, it means to perform the action in that translation spec.

Note that when a spec-id is given in a special variable, the default is to perform the translation spec named by the spec-id ignoring of any criteria statements found there. For most special variables that use a spec-id, postpending a "t" to the spec-id (with no spaces between them, eg, "${_followrel child TITLE 15t}"), will cause the criteria statements in the named translation spec to evaluate successfully before that translation spec will be processed.

_action spec-id

Use the actions of the spec identified by the SpecID with matching identifier spec-id. This behaves similarly to the Action action, but is in addition to the present translation spec.

_allatts

Print all attribute name-value pairs of the current element to the output stream. The name and value are separated by a = (equals sign), and the value is surrounded by quotes. This can be useful for creating a normalized version of the instance.

_attval attname [value] spec-id

If the current element has an attribute named attname, optionally whose value matches value, use the actions of the transpec identified by spec-id.

_chasetogi gi spec-id

Follow IDREF attributes until if finds an element whose GI is gi or which has a child element with that GI. It will apply the transpec spec-id to that element. By default, instant assumes the attributes named LINKEND, LINKENDS, and IDREF are of type IDREF or IDREFS. (This corresponds with the OSF DTDs.) You can change this by setting the variable link_atts to a space-separated list of attribute names.

_eachatt att spec-id [spec-id2]

The transpec named by spec-id is invoked once per each word found in the value of the attribute att. Inside the target transpec, the current word being processed is available in the variable named each_A (${each_A}). If spec-id2 is specified, it will use spec-id for the first word in the attribute and spec-id2 for the others.

_eachcon spec-id [spec-id2]

The transpec named by spec-id is invoked once per each word found in the content of the current element. Inside the target transpec, the current word being processed is available in the variable named each_C (${each_C}). If spec-id2 is specified, it will use spec-id for the first word in the content and spec-id2 for the others.

_env env-variable

Print the value of the environment variable env-variable to the output stream.

_filename

Print the filename of the notation associated with this element, if any. This is used to get the filename of an external notation entity reference. For example, to print the filename in the latex macro from the epsf macro package, use \\epsfboxi{${_filename}}.

_find [top] relationship args ... spec-id

Descend the document hierarchy finding elements that match one of several criteria. When one is found, the action specified by spec-id is performed. If top is specified, the search starts at the top of the document hierarchy, rather than at the current element. The possible values for relationship are gi, gi-parent, parent, and attr, and take different arguments. Explanations may be best done by example: _find gi CHAPTER 123 means to find elements whose GI is CHAPTER, and perform action 123; _find gi-parent TITLE CHAPTER 124 means to find elements whose GI is TITLE and whose parent is CHAPTER, and perform action 124; _find parent BODY 125 means to find elements whose parent's GI is BODY, and perform action 125; _find attr TYPE UGLY 125 means to find elements whose attribute named TYPE is set to UGLY, and perform action 126.

_followlink [attname] spec-id

When processing an element, instant will follow the IDREF attributes until an element with no IDREF attributes is found. It will then apply the transpec specified by spec-id to that element. If specified, it will follow the link pointed to by attname. By default, instant assumes the attributes named LINKEND and LINKENDS are if type IDREF or IDREFS. You can change this by setting the variable link_atts to a space-separated list of attribute names.

_followrel relationship gi spec-id

If the gi has the specified relationship to the current element, perform the action specified by spec-id on the related element. See the discussion of the criteria field Relation for acceptable relationship names.

_gi [M|L|U]

Print the name of the current GI to the output stream. If specified, M, L, or U will ensure the GI name is printed in mixed, lower, or upper case, respectively.

_id id [spec-id]

Find the element with id and use spec-id, if set. If not set, use the spec for that element's context.

_include filename

Insert the file filename into the output stream.

_infile [line]

Print the name of the sgml instance file to the output stream. If line is specified, also print the line number. This depends on onsgmls being called with the -l option.

_insertnode S|E spec-id

Do spec-id when the current element is traversed at a later pass. This can be considered inserting a node, without content, into the hierarchy. This is only useful if done to elements before they are processed. Typically _chasetogi or _followlink is specified early in an instance's processing, so that when the elements found by one of these actions are processed in their turn, the added actions are performed. _insertnode would be specified as the action of a spec-id pointed to in a _chasetogi or _followlink usage.

_location

The location of the current element is printed to the output stream in several ways: the path to the element (see _path), a position hint, which is the nearest title, the line number, if the ESIS (output from onsgmls) contains line numbers, and the ID of the element, if it has one. This is especially useful when using the Message action to validate an instance.

_namelist spec-id [spec-id2]

This assumes that the content of the current element is a namelist (a list of element IDs), and applies the action based on spec-id for each element pointed to. If spec-id2 is specified, it will use spec-id for the first ID in the namelist and spec-id2 for the others.

_nchild [gi]

Print the number of child elements of the element to the output stream. If gi is specified, print the number of child element with that name.

_osftable tex|tbl|check [flag]

Print table markup into the output stream. The format depends on whether tex or tbl is specified. The flag may be one of cellstart, cellend, rowstart, rowend, top, or bottom. The value determines what markup or text will be generated. If cellstart is specified, the correct markup for the beginning of a cell is output. If top, bottom, or rowend are specified, the correct markup for the end of the appropriate position is printed to the output stream. If check is specified, the attributes and child elements are checked for errors and consistency.

_path

Print the path to current GI to the output stream. A path is each element, going down the tree from the topmost element. A number in parentheses after each element name shows which child element the next one is in the order of children for that element. Ordering starts at 0. For example: OSF-BOOK(3) BODY(0) CHAPTER(4) SECTION. This says the path is <OSF-BOOK>'s third child, <BODY>'s zeroth, and <CHAPTER>'s fourth, which is named <SECTION>.

_pattr name

Print the value of parent's attribute whose name is name to the output stream.

_pfind rel gi spec-id

This is exactly the same as _find except that the search starts at the current element's parent.

_relation relationship gi spec-id [spec-id2]

If the gi has the specified relationship to the current element, perform the action specified by spec-id on the current element. If the relationship test fails and spec-id2 is specified, perform that action. See the discussion of the criteria field Relation for acceptable relationship names.

_set varname value

Set the value of the variable varname to value.

_isset varname [value] spec-id

If the value of the variable varname is set to value, then perform action referred to by spec-id. If value is not specified, action will be performed if varname is set to any value.

_! command

Run the command command, directing its standard output into the output stream.

Immediate Variables

Immediate variables are like special variables, except that they are expanded when the transpec is originally processed (special variables are processed later, near when the final output is being generated). The general syntax of immediate variables is ${+immediate_variable ...}.

There is currently only one immediate variable defined:

+content

This special variable is replaced by the data content of the current element.