The expression editor is a dialog that edits expressions. It
is used in several places, including the Scribe app using the
"Templates" tab, and the Automate app when editing template (*.xsl) and
pipeline (*.xpl) files.
Related topics and links
Automate app a no-code editor for task pipelines and content generation
Scribe app a no-code editor specifically designed for rich text content
generation
Data setup Data setup files and no-code editor
Expressions are incredibly useful. They are used to calculate values,
make decisions, generate content and more. Expressions are based on
XPath, which is a W3C-backed open standard that is widely used.
To make it easy to work with expressions, Tag offers three different
point and click editing panels. These are described below along with a
raw syntax panel.
When most logic instructions are inserted or edited, an expression
editor dialog is opened. You can move between editing panels using
radios buttons at the top.
Sometimes, moving to a different panel may cause part of an expression
to be lost. When that happens Tag prevents you from selecting the other
panel. You need to delete the existing expression before selecting an
incompatible editing panel.
Quick values panel
The Quick values panel displays all visible data fields in a
tree. You select the field you want, optionally choose a format, and
click Insert . This creates a simple expression that copies a
data value.
If the data type supports formatting, additional branches are added to
the tree to select common formats. This is shown above under the Date
of birth branch.
If variables are visible to the logic or pipeline instruction being
edited (i.e., the instruction which stores an expression like xsl:if ,
or p:if ), they will be included in the quick values tree. This
is true for xsl:param and p:option instructions as
well.
Basic panel
The Basic panel is ideal for creating true/false expressions
used to control if and choose/when instructions. It
creates conditions, which have left and right parts joined by a
comparison. An expression in this panel consists of one or more
conditions (joined by and/or).
Each of the words shown above are touch-sensitive and will display a
popup menu when clicked.
The left and right words represent data fields or literal (manually
entered) values. The center word displays a list of comparisons that are
appropriate for the type of data being compared.
true/false - equals, does not equal
numeric - equals, does not equal, <, <=, >, >=
characters - equals, does not equal, contains, starts-with,
ends-with, matches-pattern
This is how two conditions look. If you click on the 'and ' you
can change it to 'or '.
The above example shows data fields using names that contain a colon
(e.g., assessInfo:program ). The part before the colon is
called a namespace prefix, and usually corresponds to a data setup file
where the prefix matches the base file name (e.g., assessInfo:program
refers to the program data field defined in the assessInfo.rng
data setup file). Using prefixes makes it possible to use multiple data
setup files together in one report.
Advanced panel
The Advanced panel is similar to the basic
panel , but with much more functionality. It is a full-featured
touch-sensitive expression editing panel that can handle most XPath
syntax.
Each part of the expression in the advanced expression editing panel is
clickable and presents a popup menu with available options. Expression
parts can be nested and grouped within brackets.
Literal values are manually-entered strings, numbers or
true/false values. Named values and Source data
contain parts of the quick values tree.
The Path menu lets you refer to the context item or insert a
path step. The Compare / combine menu handles >, <, =,
>>, <<, and/or and similar expression operators. The Math
menu handles add, subtract, multiply and divide for number values.
The Function... menu item opens a dialog with dozens of
functions to choose from. This is described further in the next
section .
The Sequence / collection menu supports sequences, ranges,
arrays and maps. The Logic menu handles compound expression
parts like if , for , let , every
and some expressions. The Type utility supports castable
as , cast as , treat as and instance of
expressions.
Finally, the Add filter menu item lets you add one or more
predicates (filters) to narrow the currently selected sequence of
values.
Functions
The functions dialog displays a tree of all available functions. Most
are defined by the open XPath standard. These are supplemented with 1-2
dozen that are only supported in Tag.
Each function accepts zero or more arguments. In the advanced panel,
each argument is edited using its own specific popup menu. Links to more
information about each XPath function are provided in the functions
dialog.
The following screenshot shows how a format-date function
looks in the advanced panel.
Raw syntax panel
The Raw syntax panel is a text area that accepts raw XPath
syntax. In rare cases where the advanced panel
does not support what you need, this panel can handle 100% of XPath
syntax.
If errors are detected, a message is displayed beneath the text area to
describe the issue.