EPScript
EPrints 3 Reference: Directory Structure - Metadata Fields - Repository Configuration - XML Config Files - XML Export Format - EPrints data structure - Core API - Data Objects
XML Configuration: EPScript - Control Format (EPC) - Citation - Workflow - Phrase - Template - XPAGE (static pages)
NOTE: There are many functions not documented on this page. Look in ~/perl_lib/EPrints/Script/Compiled.pm for other functions.
This is an introduction.
Language Synopsis
$var{xxx} - get the value of 'xxx' in $var
$var{xxx}{yyy} - get the value of 'yyy' in 'xxx' in $var
$var.xxx(yyy) - call method 'xxx' on $var with argument 'yyy'
xxx(yyy) - call method 'xxx' with argument 'yyy'
xxx - get the value of field 'xxx'
xxx OP yyy - test whether 'xxx' is OP 'yyy' (=, !=, etc.)
xxx LOGIC yyy - test whether 'xxx' LOGIC 'yyy' (and, or, not etc.)
Examples
$config{oai}{v2}{archive_id} - gets the current OAI repository identifier
$current_user{department}.is_set() - returns true if the user's department field is set
published.one_of('submitted','published') - returns true if published is 'unpub' or 'published'
$item{type} = 'patent' - returns true if type from item is 'patent'
join($item{userid}.as_item(){collection},',') - useful for extracting data in 'multiple' fields. For the owner of the eprint, return all 'collection's as a comma-separated string. See How to control eprint workflow based on a user field
Global Variables
$config{xxx} - a value from the configuration.
$current_user - the current user, e.g., $current_user{username}
$current_lang - the id of the current language (such as 'en')
$item - the current item (usually an eprint, but not always, e.g., in citations or workflows for user objects), e.g., $item{eprintid}. If you just use eprintid it is a shortcut for $item{eprintid}
Data Types
EPScript allows for two primitive data types (string and integer) as well as providing the means to access properties of data objects such as EPrints or Users.
Primitive Types
Strings and characters
These are contained within either double quotes ("") or single quotes (''). There is no difference between the two, but it may be easier to use one sort when inside an XML attribute. For example:
<when test="type = 'patent'">
...
</when>
Integers
Integers are defined as a string of numbers from 0-9, e.g. 300. Leading zeros do not have any effect, and decimal values are currently not supported.
Booleans
True or false values. Returned by = gt and lt and oneof and used in <if> etc.
If you need to test a boolean field, see the example at the end of this page.
Data Objects
Data Objects include most of the key EPrints objects - whether an EPrint itself, documents related to the EPrint, or a user. EPScript treats all of these data objects the same, with a simple approach to retrieve properties. When an EPScript is executed, an 'item' object is supplied. In the case of a citation file, this will be the item for which the citation is being created. For a workflow, this will be the object on which the workflow acts (e.g. an EPrint or a user). Properties of main objects can be accessed using a shortened approach - the following example is from a user workflow, so the usertype property is available:
<if test="usertype = 'editor'">
...
</if>
There are cases, however, where two or more data objects may be provided - such as an EPrint and a user. Here the main item can still be accessed in the short form, but other objects use a dollar notation. In this example, the EPrint is available as $eprint:
<if test="$eprint{ispublished}.one_of('unpub', 'submitted', 'inpress')"> (<print expr="$eprint{ispublished}" />)</if>
Field Values
Values associated with a data object field. The field which the value belongs to can effect how it is rendered, and compared to other values.
Hash
This currently only used by the $config parameter to give access to configuration options. Get values out of it the same way you get values from a dataobject, eg. $config{'base_url'}
Note: To use the `$config`, you may need to wrap the whole expression in braces e.g.:
<component>
<field ref="a_set_or_named_set_field" options="{$config{default_value_for_field}}" required="yes" />
</component>
which would reference (in a cfg/cfg.d/example.pl file):
$c->{default_value_for_field} = "amstrad";
XHTML
The citation method returns a pre-rendered value. You can't do anything with XHTML other than print it.
Operators
Logical Operators
and
Returns true if both the left-hand and the right-hand expressions return true.
<if test="type = 'book' and is_set( creators )">
...
</if>
or
Returns true if at least one of the expressions returns true.
<if test="type = 'book' or type = 'patent'">
...
</if>
not
Returns true if the expression is false and false if the expression is true.
<if test="!is_set( creators )">
...
</if>
Comparison Operators
lt
Returns true if the left-hand expression is less than the right-hand expression. This is only applicable to expressions that return numeric values.
<if test="length(editors) lt 6">
...
</if>
gt
Returns true if the left-hand expression is greater than the right-hand expression. This is only applicable to expressions that return numeric values.
<if test="length(editors) gt 1">
...
</if>
equals
Returns true if the left-hand expression is equal to the right-hand expression. This applies to numeric, boolean, and string values.
<if test="type = 'patent'">
...
</if>
If the left OR the right value is a FIELDVALUE of a multiple field, then it returns true if the other value matches any of the values on the other side. eg. "subjects = 'group_foo'" will be true if any of the subjects are "group_foo".
not equals
The inverse of the equals operator, this returns true if the expressions are not equal.
<if test="type != 'book'">
...
</if>
Functions
Calling Functions
Functions can be called in two ways:
<when test="is_set( creators )">
<print expr="citation( eprint,title )">
or
<when test="creators.is_set()">
<print expr="eprint.citation( title )">
These are interchangable, but it may be beneficial to use a specific form in some cases.
Function List
is_set
Returns true if the parameter is set, based on the following criteria:
- If the parameter is a string, it is set if it is not empty.
- If the parameter is a list or a complex structure, it is set if at least one value is set.
<when test="is_set( creators )">
...
</when>
parameters: is_set(ANYTHING)
returns: BOOLEAN
length
Returns the number of items in the list.
<if test="length(editors) gt 1">s</if>
parameters: length(ANYTHING) .. although only Field Values make much sense
returns: INTEGER
one_of
Returns true if the string is in the list of strings provided.
<when test="type.one_of( 'book','book_section' )">
...
</when>
Can in theory use any type of value. Will use the "=" method to compare them.
parameters: ANYTHING.one_of( LIST )
returns: BOOLEAN
reverse
Returns the reverse of a string (i.e. 'abc' becomes 'cba').
<when test="type.reverse = 'tnetap'">
...
</when>
This function was largely used for debugging, it's not very useful...
parameters: reverse(STRING)
returns: STRING
yesno
Returns a string "yes" or "no" depending on the value of the boolean passed to it.
parameters: yesno(BOOLEAN)
returns: STRING
citation
Can only be called on a dataobject. eg. $item or $current_user. It returns the object rendered using the specified citation style.
<epc:print expr="$item.citation('default')" />
The results of citation are only really useful for rendering, not testing.
parameters: DATAOBJ.citation(STRING)
returns: XHTML data
as_item
A very useful little method. This can only be called on a field value of a field of type "itemref". It returns the item itself.
<epc:print expr="$item{userid}.as_item(){username}" />
parameters: FIELDVALUE.as_item()
returns: DATAOBJECT
to_dataobj (3.3.17+ and 3.4.2+)
This is like "as_item" but does not require the field to be of "itemref" type. It will take the variable specified and will lookup this against the DataObj type specified using the particular field specified.
<epc:print expr="$item{userid}.to_dataobj( 'user', 'userid' ).username" />
parameters: FIELDVALUE.to_dataobj( DATASET, DATAOBJ_FIELD )
returns: DATAOBJECT
subproperty (3.3.17+ and 3.4.2+)
When you have a compound field and want to print out just a sub-property of this field. This currently only works for non-multiple compound fields. E.g.
<epc:print expr="$item{compoundfield}.subproperty( 'field2' )" />
parameters: FIELDVALUE.subproperty( SUBFIELDNAME )
returns: STRING
Examples
Pluralising the editors of a book
<if test="type = 'book' and is_set(editors)">
<print expr="editors" />, (ed<if test="length(editors) gt 1">s</if>
</if>
Rendering the URL of an EPrint
<print expr="$config{base_url}" />/<print expr="eprintid" />/
Testing a boolean field
Boolean fields can be TRUE, FALSE or NULL. Just doing a test="boolean_field" isn't enough. Use this:
<if test="boolean_field = 'TRUE'">
...
</if>
