Ausdrucksmanager

Hinweis: Dieses Feature steht erst seit LimeSurvey 1.92 zur Verfügung.

Was ist der Ausdrucksmanager?

Übersicht

Um Umfragen auf die eigenen Bedürfnisse anzupassen benötigt man in der Regel folgende Möglichkeiten:

1. "Navigation/Verzweigungen" - verändert die Reihenfolge der Fragen z.B. auf Grundlage der Antworten auf vorangegangene Fragen
2. "Tailoring/Piping" - Anpassung des Fragetextes (in Bezug auf vorangegangene Frage oder die Anzahl oder das Geschlecht des Teilnehmers), oder von Berichten (Bewertungs-scores oder spezifische Empfehlungen).
3. "Validierung" - stellt sicher, daß die gegebene Anwort bestimmten Kriterien entspricht (z.B. einem Maximal- oder Minimalwert oder einem bestimmten Eingabemuster).

Mit Hilfe des Ausdrucksmanagers ("Expression Manager", EM) ist es möglich all dies in intuitiver Art und Weise umzusetzen. Nahezu alles, was man mit einer mathematischen Formel beschreiben kann, kann auch als Ausdruck dienen; sogar der Aufruf von Funktionen ist möglich. EM stellt augenblicklich >70 Funktionen bereit und kann mit relativ wenig Aufwand erweitert werden. Sämtliche Variablen aus der jeweiligen Umfrage stehen unter ihrem "menschen-lesbaren" Variablennamen zur Verfügung.

Die folgenden Abschnitte beschreiben wo der Ausdrucksmanager zu Einsatz kommt

Relevanz (für Navigation/Verzweigung)

Einige Umfrageapplikationen verwenden eine "Sprung-Logik", so dass, wenn Sie die Frage 1 mit der Option C beantworten, dann springe Sie zu Frage 5. Dieser Ansatz ist sehr begrenzt, da es schwer zu validieren ist, und leicht schief geht, wenn Sie Fragen neu ordnen. AM verwendet eine Boolesche Relevanz-Gleichung um zu spezifizieren unter welchen Bedingungen eine Frage gültig sein könnte. Wenn die Frage relevant ist, dann wird die Frage gestellt, ansonsten ist Sie Nicht Anwendbar, und der Wert NULL wird in der Datenbank gespeichert. Dies ist ähnlich zu dem, was über dem Bedingungseditor gemacht werden kann, aber mit EM können Sie einfacher viel komplexere und leistungsfähige Kriterien festlegen (und Sie können Variablennamen statt SGQA Namensgebung nutzen).

Dieses Bild zeigt einen Weg, um die Relevanz-Logik für eine Umfrage zu überprüfen. Es berechnet den Body-Mass-Index (BMI). Die Relevanz Gleichung wird in eckigen Klammern direkt nach dem Variablennamen (grün) gezeigt. So sind die Bedeutung von Gewicht (weight), weight_units, Größe (height) und height_units alle 1, was bedeutet, dass diese Fragen immer gestellt werden. Allerdings ist die Relevanz für BMI {! IS_EMPTY (height) und! IS_EMPTY (weight)}, was bedeutet, dass der BMI nur berechnet wird, wenn der Teilnehmer einen Wert für Höhe und Gewicht eingibt(wodurch das Risiko einer Division durch Null vermieden wird). Auch wird die Frage Bericht (Report) nur angezeigt, wenn der Teilnehmer Antworten auf vier Fragen (height, height_units, weight, weight_units) gibt.

Relevanz wird an folgenden Stellen gezeigt und ist bearbeitbar:

Betrachten / Bearbeiten der Relevanz auf Fragenebene

Diese Gleichung berechnet den Body-Mass-Index (BMI). Dies wird nur gefragt, wenn die Person vorher ihre Größe und Gewicht eingegeben hat.

Dies ist der Bearbeitungs-Bildschirm für die BMI Frage.

Beachten Sie, dass Sie geschweiften Klammern nicht nutzen dürfen, wenn Sie eine Relevanz Gleichung eingeben.

Betrachten / Bearbeiten Relevanz auf Gruppenebene

This is a sample census survey.  The first page asks how many people live with you and stores that in the "cohabs" variable.  This page is only shown if you have more than one cohabitant (so it is shown for the second person cohabitating with you), and also only shows if you specified how Person One is related to you (p1_rel).

As you can see, the group also has question-level relevance criteria, such that each question only appears once you have answered the question before it (e.g. {!is_empty(p1_sex)}).  EM combines the Group and Question-level relevance for you.  Questions in a group are only asked  if the group as a whole is relevant.  Then, only the subset of questions within the group that are relevant are asked.

Here is the screen for editing the group-level relevance for that question:

Beachten Sie, dass Sie geschweiften Klammern nicht nutzen dürfen, wenn Sie eine Relevanzgleichung eingeben.

Tailoring/Piping

EM lets you easily do simple and complex conditional tailoring of your questions.  Sometimes you just need simple substitution, like saying, "You said you purchased [Product].  What did you like best about it?".  Sometimes you need conditional substitution like "[Mr./Mrs.] [LastName], would you be willing to complete our survey?".  In this case,  you want to use Mr. or Mrs. based upon the person's gender.  Other times you need even more complex substitution (such as based upon a mathematical computation).  EM supports each of these types of tailoring/piping.

Bedingte Gleichungen

The Body Mass Index example shows the ability to compute a person's BMI, even while letting them enter their height in weight in metric or non-metric units.

Here weight_kg is {if(weight_units == 'kg', weight, weight * .453592)}.  This if() function means that if the subject entered the weight using kilograms, use that value, otherwise multiple the entered value (which was in pounds) by .453592 to convert it to kilograms.  The height_m variable uses a similar approach to compute the person's height in meters, even if he entered his height in inches.

BMI computes the weight formula as {weight_kg / (height_m * height_m)}.

Lastly, the report conditionally tailors the message for the subject, telling him what he entered. ("You said you are 2 meters tall and weight 70 kg.")

Although not well shown in the above image, weight_status uses nested if() statements to categorize the person as underweight to severely obese.  You can see its equation in the Show Logic View

From the edit window for this question, you can see two things:

1. Tailoring must surround expressions with Curly Braces
2. Expressions can span multiple lines if, as in this case, you want to make it easier to read the nested conditional logic.

Tailored Questions, Answers, and Reports

Note: Dynamic tailoring may not work if answer options are made available in select boxes on the same question page. This results from the fact that tailoring inserts a <span> tag which is not valid inside select options.

Dieses Beispiel zeigt den BMI-Bericht.

Hier ist das Bearbeitungs-Fenster für die gleiche Frage.

As you can see, anything in curly braces is treated as an expression, so is syntax-highlighted (color coded) in the prior image.  If you had any typos (such as misspelled or undefined variable names or functions), EM would show an error, such as this, showing that height_unit is an undefined variable name (it is actually height_units), and rnd() is an undefined function (the proper function name is round()).  In both cases, the errors are surrounded by a red box to make it easier to spot and fix them.

You can also see that you can quickly create complex reports, such as a table of entered values or tailored advice.

Please remember that all tailoring must surround expressions with Curly Braces, so that LimeSurvey knows which parts of the question are free text and which should be parsed through Expression Manager.

Validierung

EM controls how most of the advanced question options work.  These control aspects like min/max numbers of answers; min/max individual values; min/max sum values; and checking that entered values match specified string patterns.  You continue to enter those advanced question options as usual.  However, now any value in one of those fields is considered an expression, so you can have min/max criteria with complex conditional relationships to other questions.

In all of these cases, since the advanced question option is always considered an expression, you do not use curly braces when specifying it.

The Sample Surveys pages shows many working examples of using expressions for validations.

Einführung

LimeSurvey 1.92 and later uses the new Expression Manager (EM) module which will let LimeSurvey support more complex branching, assessments, validation, and tailoring.  It will replace how LimeSurvey manages Replacements, Conditions, and Assessments on the back-end.  It will also speed up processing considerably since it eliminates most run-time database reads.  EM was developed by Dr. Thomas White (TMSWhite).

This wiki page is the definitive reference for Expression Manager syntax and functionality.

Key Definitions

1. Expression:  Anything surrounded by curly braces
   • As long as there is no white space immediately after the opening brace or before the closing curly brace
   • The contents of Expressions are evaluted by EM, so they can contain mathematical formulas, functions, and complex string and date processing.
2. Tailoring: Sometimes called "piping", this is the process of conditionally modifying text
   • You have access to all 'replacement fields', TOKENs, and INSERTANS values
   • You also have easier access to questions, answers, and their properties.
3. Relevance Equation:  A new question attribute controlling question visiblity
   • If there is a relevance equation, then the question is only shown if the relevance evaluates to true.
   • Internally, all array_filter and array_filter_exclude commands become subquestion-level relevance
4. Equation Question Type:  A new question type that saves calculations or reports to the database
   • It is like a Boilerplate question, but its contents are saved to the database even if you set "Always Hide this Question"
5. SGQA:  This is how variables are named in LimeSurvey <= 1.91+
   • Stands for Survey-Group-Question-Answer
   • SGQA variable names look like 123X5X382X971, and may have subquestion suffixes.
   • These variable names are specific to the underlying S/Q/G/A database codes, so often need to be changed
6. Question Code:  This is the preferred variable name for EM
   • This can be a descriptive name indicating the purpose of the question, making it easier to read complex logic
   • Although not required to be unique in <= 1.91+, it must be unique if you want to use EM
   • Valid question codes should NOT start with a number, so when using the question code to number your questions, simply use "q1", or "q1a" or "g1q2".
   • This is what currently becomes the variable name if you export data to SPSS or R, so if you do statistical analysis, you probably already made this unique.

Muss ich den AM benutzen?

Die kurze Antwort ist Nein (aber auch Ja).

EM is fully backwards-compatible with existing surveys.  So, if you are happy to use Conditions and Assessments in the style that LimeSurvey used in versions <= 1.91+, you can continue to do so.

However, EM completely replaces how LimeSurvey internally deals with Conditions.  Although you can still use the Conditions Editor to create and manage conditions, LimeSurvey 1.92 will convert those to the equivalent Relevance Equations.  As part of the upgrade, LimeSurvey 1.92 will auto-convert all existing Conditions to Relevance Equations.

This should give you the best of both worlds - you can continue using LimeSurvey as you are used to, but will see the Relevance Equation equivalent so you can gradually migrate to Relevance Equations directly whenever you see fit.

Kann ich eine Mischung aus Bedingungen und Relevanz nutzen?

Yes. You can use the Conditions editor for some questions and the Relevance editor for others.  Conditions are auto-converted to Relevance when you save the question.

Note, we assume that if you are using the Conditions editor, that you want those Conditions to over-write any manually entered Relevance equation.  So, if you have existing Conditions and want to manually edit the Relevance, please delete the Conditions for that question first.  Specifically, copy the generated relevance equation to a text editor, use the Conditions menu to delete all of the conditions for that question (which will also delete the relevance), then edit the question and paste the generated relevance equation from the text editor back into the relevance field for that question (and save the question).  If there is enough demand for deleting conditions without deleting the generated relevance equation, we could add a bulk conversion process.

How should I choose between Conditions and Relevance?

Here is a list of pros and cons of each style:

Style	Pros	Cons
Conditions	1. Nice GUI for creating simple conditions 2. GUI well documented and understood by support team	1. Only supports simple comparisons and does not AND/OR conditions well 2. Cascading conditions work erratically 3. Slow - database intensive, so can slow down long surveys 4. Some reported problems with re-loading conditions 5. GUI doesn't scale well when there are dozens, hundreds, or thousands of questions 6. May be slow to convert paper-based surveys since must use SGQA names 7. Often need a programmer to custom-code logic needed for complex branching
Relevance	1. Supports very complex logic, including 80+ functions and math/string operators 2. Perfect support for cascading logic 3. Fast - no extra database calls, so supports 1000+ question surveys 4. No problems with re-loading logic since does not require SGQA codes 5. Syntax-highlighting scales to 1000+ question surveys 6. Easy and fast to use for groups wanting to computerize existing paper-based suveys.   7. Easily supports semi-structured interviews and epidemiological surveys without needing a programmers	1. No GUI for simple conditions - use syntax-highlighting instead 2. New, so support teams have not mastered EM yet.

The bottom is that if you are happy with how LimeSurvey 1.91+ works, there is no reason to change what you do.

Was sind andere Vorteile der Verwendung von AM?

Here are some of the other reasons you might want to use EM.

1. Calculations - you can create any calculation you can think of:
   • You have access to all common mathematical operators and functions
   • You have access to 70+ mathematical, date, and string processing functions
   • It is fairly easy for developers to add new functions if users need them
2. Storing Calculations to Database
   • You can now compute simple and complex calculations and/or scale scores AND have them stored in the database without needing JavaScript.
   • You use the Equation question type to accomplish this.
3. Assessments
   • You can now create assessments or scale scores from any question type, not just the subset that used to be supported
   • You can use Tailoring to show running or total assessment scores anywhere needed - even on the same page
   • You have more control over the reports generated based upon those assessment scores
   • You can store assessment scores in the database without needing JavaScript
   • You can hide assessment scores without needing JavaScript or CSS
4. Replacement Fields
   • Instead of using {INSERTANS:SGQA}, you can just use the Question Code - this makes it easier to read and validate.
   • This also avoids the common need to edit questions to change the SGQA code to make everything work.
5. Tailoring - you can conditionally display text based upon other values
   • Use the appropriate title for a subject, like (e.g. "Hello [Mr./Mrs.] Smith")
   • Output gramatically correct sentences based when singular/plural matter:  (e.g. "You have 1 child" vs. "You have 2 children")
   • Appropriately conjugate verbs and decline nouns based upon subject's gender and plurality.
6. New Variable Attributes - you can access the following to do your tailoring:
   • (no suffix) -  an alias for qcode.code
   • .code - the selected response code for the question if it is relevant (otherwise blank), or the text value if it is not a coded question
   • .NAOK - same as .code, but can be part of calculations or lists even if irrelevant
   • .value - the assessment value for the question if it is relevant (otherwise blank), or the text value if it is not a coded question
   • .valueNAOK - same as .value, but can be part of calculations or lists even if irrelevant
   • .shown - the answer as displayed to the user (this is what {INSERTANS:xxx}  does)
   • .qid - the question ID
   • .gid - the group ID
   • .sgqa - the SGQA value for the question
   • .jsName - the correct javascript variable name for the question, regardless whether defined on this page or another
   • .qseq - the question sequence (starting from 0)
   • .gseq - the group sequence (starting from 0)
   • .mandatory - whether the question is mandatory (Y/N)
   • .question - the text of the question
   • .relevance - the relevance equation for the question
   • .grelevance - the relevance equation for the group
   • .relevanceStatus - whether or not the question is currently relevant (1 if true, 0 if false)
   • .type - the question type (the one character code)
7. Dynamic On-Page Changes
   • All Relevance, Calculation, and Tailoring works dynamically on a page - so changes in values instantly update the page
   • So, you have questions dynamically appear/disappear based upon whether they are relevant
   • Questions are also dynamically tailored based upon responses on the page, so you can see running totals, tailored sentences and customized reports.
8. New Data Entry Screen
   • In addition to using the current data-entry system, you can just use Survey-All-In-One.
   • This supports the on-page relevance and tailoring, so data entry clerks can quickly tab through and they will only have to enter the relevant responses
   • This can be critical if your data entry person needs to see the tailoring, which is also dynamic.
9. Eliminates the need for most custom JavaScript
   • EM easily supports complicated computations, scoring, tailoring and conditional logic.
   • Some things will still need JavaScript (like custom layouts and conditionally hiding question sub-elements), but your JavaScript can use the EM functions so that you can access questions by their Qcode instead of SGQA, and access any of the question properties listed above.

What are some other helpful new features enabled by EM?

Regardless of whether you continue to use the Conditions Editor or manually compose Relevance Equations, you get these additional benefits:

1. You can create more complex validation criteria
   • All of the advanced question attribute (like max_answers, min_num_value_n, max_num_value) can use Expressions.  So, you min/max criteria can be easily adjusted based upon prior responses, even if they are on the same page.
   • EM also handles all regular-expression-based validation, so you can robustly combine preg and equation-based question attributes.
2. Easy Re-ordering (or deleting) of Questions and Groups
   • Prior to version 1.92, you could not re-order questions or groups if LimeSurvey thought that such-re-ordering could break conditions in which they were used.  Similarly, you could not delete questions if any other questions depended upon them.
   • With EM's syntax highlighting, it is easy to see and validate whether you try to use questions before they are declared.  So, we now let you re-order or delete questions and groups whenever you like.  EM will update all of the syntax highlighting to show you potential errors.
   • The re-order questions view has been enhanced to help with such review.  It now shows the question's relevance equation and tailoring, so you can immediately see whether any variables become pink (meaning they are used before being declared).
3. The Question/Group Navigation Index is always available and accurate
   • Prior to version 1.92, these indexes were not available if there were complex conditions
   • With EM, we can guarantee that they are accurate.
   • Subjects can even jump back, to a prior question, change the answer, then jump forward (or submit)
     • When jumping forwards, EM will re-validate all of the intervening questions/groups.
     • If any questions become irrelevant, they will be NULLed in the database so that your data is internally consistent
     • If any questions become relevant or newly fail mandatory or validation rules, EM will stop on that page and force the user to answer those questions before jumping to their final destination.
4. Auto-conversion of Conditions to Relevance
   • When you upgrade your database, all existing surveys that have conditions will have relevance equations generated for them
   • Whenever you import a survey, relevance equations will be created as needed
   • Whenever you add, delete, or modify conditions, EM will generate the appropriate relevance equation.
5. Convenient Syntax Highlighting
   • When EM shows the relevance equation, it will show the Qcode, even if you entered an SGQA code, as we assume this will be easier to read.
   • All variables are color coded to show whether they were declared before or after the current question (or before or after the current group).  This lets you quickly detect and fix cases where you try to use variables for relevance (including array_filter), tailoring, or validation equations prior to declaring them.
   • In addition, if you hover your mouse over the color-coded variable, you will see the most important metadata about that question.   This includes the Group Sequence #, Question Sequence #, Qcode, Text of the question, and all available answer choices (if it is a question type with enumerated answer choices).
     • The list of answer choices uses this syntax:  'answers':{key:val, ... }.
     • key has the syntax 'scale~code' where scale is the answer scale (e.g. for dual scale), and code is the answer code.
     • val has the syntax 'value~shown' where value is the assessment value (if using assessments, otherwise code)(e.g. Qcode.value), and shown is the display value as seen by the subject (e.g. Qcode.shown)
     • This means that many surveys can use calculations without needing assessment mode.  If you have enumerated answer options  that are unique, non-decimal, and non-negative, you can simply do calculations on the Qcode.code values.
6. Easy review of entire survey logic and content
   • There is a new Show Survey Logic feature that lets you see everything about the survey (or group or question) on a single page.
   • It shows the Group, Question, Sub-Question, and Answer-level details for the selected scope (survey vs. group vs. question)
   • It also shows the relevance, subquestion-level relevance (for array_filter and array_filter_exclude), and generated validation equation (for preg and any validation rules like min/max sum/number of values), and all non-blank question attributes.
   • Everything is syntax-highlighted so that you can see potential syntax errors (like unbalanced parentheses or use of variables before they were declared)
   • The syntax-highligting supports rapid navigation and editing of the survey.
     • If you click on a variable name, it opens a browser window (or tab) that shows you that question and lets you edit it.
     • If you click on a group name, it opens a browser window (or tab) showing the group-reorder view so that you can easily move questions around.
     • All of the question attributes are also syntax highlighted.  This lets you set and see expressions within advanced question options (like basing the max/min number/sum of values on an expression)
   • The EM author used similar view (a little cleaner) to let his collaborating Epidemiologists and Institutional Review Board validate and authorize surveys with thousands of questions in highly branched and tailored structured interviews

Wie rückwärtskompatibel ist der AM mit 1.91+?

LimeSurvey 1.92 is fully backwards-compatible with 1.91+ with one exception/caveat:  1.92 handles less-than / greater-than comparisons against empty values differently than 1.91+.

Der Ausdrucksmanager ist ein Kernmodul welches LimeSurvey ermöglicht, komplexere Verzweigungen, Beurteilungen, Validierungen und Zuschnitte zu unterstützen. Außerdem wird es nicht nur neue Funtionen unterstützen, sondern die Art und Weise, mit der LimeSurvey Ersetzungen, Bedingungen und Beurteilungen verwaltet, am Backend ersetzen. Außerdem werden die Bearbeitungen viel schneller ablaufen, da auf die meisten Datenbankzugriffe während der Laufzeit verzichtet werden kann. Der Ausdrucksmanager wurde von Dr. Tom White (TMSWhite) entwickelt.

Auf dieser Wiki-Seite befindet sich eine Anleitung für die Syntax und Funktionalität des ExpressionManagers.

Erste Schritte

The best way to get started with EM is to:

• Install the latest stable version from http://www.limesurvey.org/en/download
• Import and explore the sample surveys.
• Explore the use cases and HowTos and step-by-step examples.
• Explore the EM documentation (this page)
• Examine the built-in EM test suite
  • From any survey, under tools, select the EM option
  • Available Functions lists the 70+ functions and syntax
  • Unit Tests of Isolated Expressions
    • shows examples of using all EM functions and operators, and the PHP and JavaScript results
    • note there are few functions that generate different results in the PHP and JavaScript versions, so this page lets you plan your EM logic accordingly.

Welche Funktionalität erweitert/ersetzt der Ausdrucksmanager? (LimeSurvey <= 1.91+)

Bewertungen => Gleichungen und Micro-Tailoring

Mit Bewertungen konnten Benutzer Punktzahlen aus einer Sammlung von Fragen erstellen. Jedoch passten sie sich nicht dynamisch an die aktuelle Seite an und die Werte waren nicht in der Datenbank abgespeichert. Man musste außerdem die LimeSurvey Datenbanken anpassen.

Ersatz => Micro-Tailoring

Benutzer konnten einige Nachrichten und Fragen anhand der vorherigen Antworten anpassen. Eine Frage könnte zum Beispiel {TOKEN:VORNAME}, und Sie sagten noch, dass {INSERTANS:111X3X4} Ihre Lieblingssportart wäre sein. Jedoch konnte man nicht bedingt anpassen, Verben konjugieren oder Nomen deklinieren ohne JavaScript zu benutzen.

Replacements => Micro-Tailoring

Users could tailor some messages and questions based  upon prior responses.  For example, a question might be, {TOKEN:FIRSTNAME}, you said {INSERTANS:111X3X4} was your favorite sport.  However, it was not possible to do conditional tailoring (like say "Mr." or "Mrs." depending upon the person's gender), or conjugate verbs or decline nouns without fancy JavaScript.  Authors could implement surveys that seemed to tailor questions, but it required separate questions for each permutation, and complex conditions to decide which questions to display.

Validierung

Fragen konnten mit regulären Ausdrücken, oder mit Minimal- oder Maximalwerten validiert werden. Außerdem konnte man eine SGQA Antwort als Mindest- oder Höchstbetrag nehmen. Jedoch konnten Berechnungen von anderen Variablen ohne JavaScript nicht für die Überprüfungen verwendet werden.

Gleichungen

Gleichungen wurden ohne JavaScript nicht unterstützt.

Gleichungs-Fragetyp

Gleichungen konnten ohne JavaScript nicht in der Datenbank abgespeichert werden (zum Beispiel die Endpunktzahl für eine Beurteilung).

Wie wird der Ausdrucksmanager diese Funktion ersetzen oder erweitern?

Der Ausdrucksmanager ist ein neues Modul in LimeSurvey, es stark vereinfacht komplexe Funktionen zu unterstützen für die früher angepasstes JavaScript verwendet werden musste. Er ersetzt auch die Art und Weise mit der LimeSurvey Bedingungen und Beurteilungen verwaltet.

Neue Bezeichnungsweisen des Ausdrucksmanagers

Der Ausdrucksmanager "denkt" über seine Funktionalität folgend:

• Relevanzbasierte Verzweigung - ist eine Frage relevant, stelle sie, ansonsten nicht (z.B. mach sie unsichtbar)
• Anpassung - Sobald du weißt, welche Fragen gestellt werden sollten, wird durch das Micro-Tailoring angegeben wie die Fragen zu stellen sind. Dadurch können sie nicht nur einfache Dinge austauschen (wie z.B. {TOKEN:VORNAME}), sondern auch die Konjungation von Verben und Deklination von Substantiven basierend auf dem Geschlecht und der Anzahl der Subjekte durchführen. Es erlaubt dir auch die Antwort danach zu verändern, ob die anderen Fragen (oder wie die anderen Fragen) beantwortet wurden.
• Gleichung - Der Ausdrucksmanager fügt auch einen neuen Fragetypen namens Gleichungen hinzu, der die Ergebnisse der Ausdrücke speichert. Der eine Zeichentyp für Gleichungen ist das Asterixzeichen "*".

Relevanz und Kaskadierende Relevanz

Every question type now has a Relevance option which controls whether the question is displayed.  EM processes each of the Relevance Equations in the order they should appear in the survey.  If the expression is true (or missing - to support legacy surveys), the question will be displayed. If it is not relevant, then the question will be hidden, and the value will be NULLed in the database.  If there are no relevant questions in a group, the entire group will be skipped.

Moreover, if any of the variables within an expression is irrelevant, then the expression always evaluates to false.  This enables Cascading Relevance so that you do not have to write very long Relevance equations for each question.

Sagen wir mal, dass es 5 Fragen, Q1-Q5 gibt. Du willst aber nur, dass Q2 angezeigt wird, wenn Q1 beantwortet wurde, und Q3 wenn Q2 beantwortet wurde und so weiter. Die notwendigen Gleichungen wären dann:

Frage-Nummer	Relevanz	Frage
Q1	1	Wie heißen Sie?
Q2	Q1	{Q1}, wie alt sind Sie?
Q3	Q2	Also, Sie sind {Q2} Jahre alt. Sind Sie verheiratet?
Q4	Q3 == "Y"	{Q1}, wie lange sind Sie schon verheiratet?
Q5	Q4	Wie viele Kinder haben Sie, {Q1}?

Diese Berechnungen werden auch von JavaScript unterstützt - also können Sie die Fragen auf einer Seite platzieren und alles funktioniert weiterhin.

As long as you are on the same page, any data you entered will still be there, just hidden.  So, if you enter some information, then choose an option that makes them irrelevant, then make them relevant again, your answers will still be available.  However, as soon as you move to a different page, all irrelevant responses will be lost to integrity of the dataset.

Group-Level Relevance

Expression Manager also supports group-level relevance.  This makes it easier to implement looping.   Say you want to collect information about up to 10 entities (such a products or people in a household), where you first determine how many entities need follow-up (such as by asking how many people live in a household, or having people check which products they like from a long list).  After knowning how many entities need follow-up, you can use Group-level relevance like {count >= 1}, {count >=2}, ... {count >= 10} for each of the 10 groups of follow-up questions.  Within each group, you can have question-level conditional logic (e.g. gender or age-specific follow-up questions for each subject).  The question and group-level relevance equations are ANDed together to determine which should be shown.

Tailoring / Piping

Alles innerhalb von geschweiften Klammern wird nun als Ausdruck behandelt (mit einer Ausnahme, die unten beschrieben wird). Ausdrücke haben zugang zu allen LimeReplacement-Feldern, zu allen Variablen (über verschiedene Aliase), allen typischen Gleichungsoperatoren (mathematisch, logisch und Vergleich) und dutzenden Funktionen (die sogar dynamisch auf Client-Seite funktionieren).

Durch die Benutzung dieser Gleichungen, kannst du z.B. solche Dinge machen:

1. Den Befragten maßgeschneiderte Nachrichten abhängig von früheren Antworten zeigen
2. Beurteilungen erstellen und die Beurteilungsergebnisse (oder bedingte Verzweigungen oder Nachrichten) basierend auf diesen Ergebnissen anzeigen lassen. Alles ohne das Beurteilungsmodul selber zu benutzen.
3. Verben konjugieren und Nomen deklinieren
4. Sich Zusammenfassungen der Antworten vor der "Antworten anzeigen" Seite am Ende der Umfrage anzeigen lassen

Gleichungen

Es gibt einen neuen Fragetyp namens Gleichung. Er ist wie eine Boilerplate-Frage, bis darauf, dass er den gezeigten Wert in der Datenbank speichert. Also wenn der Gleichungs-Frage-Text eine Beurteilungs-Berechnung enthält, dann würde dieser Wert in der Datenbank in einer Variable, die in öffentlichen oder begrenzten Statistiken angezeigt werden kann, gespeichert werden.

Dies löst ein häufiges Featurerequest Beurteilungs-Wertungen in der Datenbank speichern zu können.

Syntax

Alles innerhalb von geschweiften Klammern wird jetzt als Ausdruck angesehen (mit einer Ausnahme: es darf keine führenden oder nachfolgenden Leerzeichen geben - dies ist notwendig, damit der Ausdrucksmanager nicht versucht eingebettetes JavaScript auszuführen).

Note, it is OK for expressions to span multiple lines, as long as there is no whitespace after the opening  curly brace or before the closing curly brace.  This is especially helpful for nested if() statements like this:

{if(is_empty(PFTotals),
 '',
 if(PFTotals >= -5 && PFTotals <= -4,
   'Very Soft',
   if(PFTotals >= -3 && PFTotals <= -2,
     'Soft',
     if(PFTotals == -1,
       'Somewhat Soft',
       if(PFTotals == 0,
         'Moderate',
         if(PFTotals == 1,
           'Somewhat Hard',
           if(PFTotals >= 2 && PFTotals <= 3,
             'Hard',
             if(PFTotals >= 4 && PFTotals <= 5,
               'Very Hard',
               ''
             )
           )
         )
       )
     )
   )
 )
)}

Der Ausdrucksmanager unterstützt folgenden Syntax:

• Alle Standardmatheoperationen (e.g. +,-,*,/,!)
• Alle Standardvergleichsoperationen (e.g. <,<=,==,!=,>,>=, sowie diese Äquivalenten:  lt,le,eq,ne,gt,ge)
• Klammern (Sodass Unter-Ausdrücke gruppiert werden können)
• Bedingungsoperatoren (e.g. &&,| | und diese Äquivalente: and,or)
• Zeichenketten mit einfachen oder doppelten Anführungszeichen (die jeweils Zeichenketten mit dem anderen Anführungszeichen einbetten können)
• Kommaoperatoren (Sodass Sie eine Liste von Ausdrücken haben können und nur das endgültige Ergebnis zurückgeben)
• Zuordnungsoperatoren (=,+=,-=,*=,/=)
• Vordefinierte Variablen (um sich auf Fragen und Antworten zu beziehen).
• Vordefinierte Funktionen (mit der Möglichkeit weitere hinzuzufügen)

Operators

EM syntax follows normal operator precedence:

Level	Operator(s)	Description
1	()	parentheses for grouping or calling functions
2	! - +	unary operators: not, negation, unary-plus
3	* /	times, divide
4	+ -	plus, minus
5	< <= > >= lt le gt ge	relative comparisons
6	== != eq ne	equality comparisons
7	and	logical AND
8	or	logical OR
9	=	assignment operator
10	,	comma operator

Note, for consistency between JavaScript and PHP, the plus operator (+) does addition if both operands are numeric, but does concatenation if both parts are non-numeric strings.  However, we recommend using the join() function for concatenation, as that makes your intent more clear, and avoids unexpected results if you were expecting strings but got numbers instead (or vice versa).

Caution about using Assignment Operator (=)

Note, you should avoid using the assignment operators unless absolutely necessary, since they may cause unexpected side-effects.  For example, if you change the value of a previous response, the cascading relevance and validation logic between that question and the current question is not re-computed, so you could end up with internally inconsistent data (e.g. questions that stay answered but should have been NULLed, or questions that are skipped but should have been answered).  In general, if you want to assign a value to a variable, you sould create an Equation question type, and use an expression to set its value.  However, there are some rare times that people really need this operator, so we made it available.

To help caution you about this operator, it is shown in red font within the syntax equations (so that you don't confuse it with "==")

Using Assignment Operator

The main reasons you may want to use assignment are:

• You need to set the default value for a question that does not accept defaults via equation (such as list radio, where the user interface lets you pick one of the answer options, but does not let you enter an equation).  However, be careful, as LimeSurvey will not be able to validate that your equation generates one of the allowable answers for that question.
• You need to forcibly change the response to a previous question based upon a later response
• etc...

You can use all expression manager system for this purpose. It's better to use an Equation question type to this purpose.

Some example:

• Set answer to a short text question in lowercase : {QCODE=strtolower(QCODE.NAOK)}
• Set an answer with condition : {QCODE=if(YesNo="Y","A1","")}

XSS security

With XSS enable, some expression manager system can not be used :

• starting a HTML tag in expression but ending in another expression
• use a complex expression in URL.

Example and workaround

• {if( 1 ,"<strong>","")}information{if( 1 ,"</strong>","")} is broken with XSS security, here you can use {if(1,"<strong>information</strong>","information")}
• <a href="/script.php?value={if(QCODE == "Y","yes","no")}">next</a>, here you can use an equation question because using a complete question code is OK : <a href="/script.php?value={EQUATION.NAOK}">next</a>

Zugang zu Variablen

Expression Manager provides read-only access to whichever variables we might need.  For backwards compatibility, it provides access to the following:

• TOKEN:xxx - the value of a TOKEN (e.g. TOKEN:FIRSTNAME, TOKEN:ATTRIBUTE_5) (Only for NOT anonymous survey).
• |INSERTANS:SGQA - the display value of an answer (e.g. "Yes"). For Expression Manager it's the same that using {QCODE.shown}.
• All {XXX} values used by templates
• In question text, you can use {QID} replaced by the question id and {SGQ} replaced by the SGQA of the question

Zusätzlich erlaubt dir der Ausdrucksmanager dich auf Variablen über die Frage-Nummer zu beziehen (auch als Titel in der Datenbank bezeichnet). Dies ist auch das Label der Variable, welches genutzt wird, wenn Sie Ihre Daten zu SPSS, R oder SAS exportieren. Zum Beispiel, wenn Sie Fragen zu dem Namen, Alter und Geschlecht haben, könnten sie ihre Variablen "name", "alter" und "geschlecht" nennen. Dies macht die Gleichungen jedem leichter Verständlich und macht es möglich die Fragen durch zu mischen ohne ein Auge auf die Gruppen und Fragennummern haben zu müssen.

Important: It is only safe to refer to variables that occur in preceding pages or questions.

Außerdem erlaubt der Ausdrucksmanager auf bestimmte Eigenschaften der Fragen zuzugreifen.

Syntax	Meaning	Example	Example Result
Qcode	an alias for Qcode.code	{implode(',',name,gender)}	'Tom','M'
Qcode.code	the selected response code for the question if it is relevant (otherwise blank), or the text value if it is not a coded question	{implode(',',name.code,gender.code)}	'Tom','M'
Qcode.NAOK	same as Qcode - see discussion of NAOK	{gender.NAOK}	'M'
Qcode.value	the assessment value for the question if it is relevant (otherwise blank), or the text value if it is not a coded question	{gender.value}	'1'
Qcode.valueNAOK	same as Qcode.value - see discussion about NAOK	{gender.valueNAOK}	'1'
Qcode.shown	the dispay value for the question	{implode(',',name.shown,gender.shown)}	'Tom','Male'
Qcode.question	the text of the question	{gender.question}	'What is your gender?'
Qcode.mandatory	whether the question is mandatory (Y/N)	{gender.mandatory}	'N'
Qcode.qid	the internal question number (not the sequential number)	{gender.qid}	337
Qcode.type	the question type	{gender.type}	'G'
Qcode.jsName	the correct javascript name for the question, regardless whether declared on or off this page	{gender.jsName}	'java1827X3X337'
Qcode.gid	the internal group number (not the sequential number)	{gender.gid}	3
Qcode.qseq	the sequential number of the question, starting from 0	{gender.qseq}	5
Qcode.gseq	the sequential number of the group, starting from 0	{gender.gseq}	1
Qcode.relevanceStatus	whether the question is currently relevant (0 or 1)	{gender.relevanceStatus}	1
Qcode.relevance	the question-level relevance equation	{gender.relevance}	'!is_empty(name)'
Qcode.grelevance	the  group-level relevance equation	{gender.grelevance}	'num_children >= 5'
Qcode.sgqa	the SGQA value for this question	{gender.sgqa}	'1827X3X337'

HTML editor issue

  This issue is fixed after 2.06 build 140803

If you use HTML editor, some characters are replaced by HTML entities.

• & by &amp;
• < by &lt;
• > by &gt;

If you use HTML editor you need to use :

• and for &
• lt for <
• le for <=
• gt for >
• ge for >=

Qcode Variable Naming

Hier sind die Details, wie ein Qcode konstruiert wird (und auf einige Eigenschaften zugegriffen wird), geordnet nach Fragetyp. Generell werden Qcodes wie folgt konstruiert:

 QuestionCode . '_' . SubQuestionID . '_' . ScaleId

For comment and other, question code are QuestionCode_comment and QuestionCode_other

Type	Description	Code	SubQs	Answer Options	Scales	Answer Code	Answer Shown	Relevance
5	5 Point Choice Radio-Buttons	Q1		1-5		{Q1}	{Q1.shown}	{Q1==3}
B	Array (10 Point Choice) Radio-Buttons	Q2	L1-L6	1-10		{Q2_L2}	{Q2_L2.shown}	{Q2_L2==7}
A	Array (5 Point Choice) Radio-Buttons	Q3	1-5	1-5		{Q3_1}	{Q3_1.shown}	{Q3_1>=3}
1	Array (Flexible Labels) Dual Scale	Q4	sq1-sq5	0:a1-a3	1:b1-b3	{Q4_sq1_0}	{Q4_sq1_1.shown}	{Q4_sq1_1=='b2'}
H	Array (Flexible) - Column Format	Q5	1-5	s,m,t		{Q5_1}	{Q5_1.shown}	{Q5_1=='s'}
F	Array (Flexible) - Row Format	Q6	F1-F5	1-5		{Q6_F3}	{Q6_F3.shown}	{Q6_F3==4}
E	Array (Increase/Same/Decrease) Radio-Buttons	Q7	1-7	I,S,D		{Q7_4}	{Q7_4.shown}	{Q7_4=='D'}
:	Array (Multi Flexi) 1 To 10	Q8	ls1,todo,ls2	min,max,avg		{Q8_ls1_max}	{Q8_ls2_avg.shown}	{Q8_ls2_min==7}
;	Array (Multi Flexi) Text	Q9	hp,st,sw	1st,2nd,3rd		{Q9_hp_3rd}	{Q9_hp_3rd.shown}	{Q9_hp_3rd=='Peter'}
C	Array (Yes/Uncertain/No) Radio-Buttons	Q10	1-5	Y,N,U		{Q10_1}	{Q10_1.shown}	{Q10_3=='Y'}
X	Boilerplate Question	Q11					{Q11.shown}
D	Date	Q12				{Q12}	{Q12.shown}
*	Equation	Q13				{Q13}	{Q13.shown}	{Q13>5}
~124~	File Upload (records number of files uploaded)	Q14				{Q14}		{Q14>0}
G	Gender Drop-Down List	Q15		M,F		{Q15}	{Q15.shown}	{Q15=='M'}
U	Huge Free Text	Q16				{Q16}	{Q16.shown}	{strlen(Q16)>100}
I	Language Question	Q17				{Q17}	{Q17.shown}	{Q17=='en'}
!	List - Dropdown	Q18		1-5		{Q18}	{Q18.shown}	{Q18==3}
L	List Drop-Down/Radio-Button List	Q19		A-Z		{Q19}	{Q19.shown}	{Q19=='X'}
O	List With Comment Drop-Down/Radio-Button List + Textarea	Q20		A-F		{Q20},{Q20comment}	{Q20.shown}	{Q20=='B'}
T	Long Free Text	Q21				{Q21}	{Q21.shown}	{strstr(Q21,'hello')>0}
M	Multiple Choice Checkbox	Q22	A-F			{Q22_E}	{Q22_E.shown}	{Q22_E=='Y'}
P	Multiple Choice With Comments Checkbox + Text	Q23	A-F			{Q23_D}, {Q23_Dcomment}	{Q23_D.shown}	{!is_empty(Q23)}
K	Multiple Numerical Question	Q24	self,mom,dad			{Q24_self}	{Q24_self.shown}	{Q24_self>30}
Q	Multiple Short Text	Q25	A-F			{Q25_B}	{Q25_B.shown}	{substr(Q25_B,1,1)=='Q'}
N	Numerical Question Type	Q26				{Q26}	{Q26.shown}	{Q26 > 30}
R	Ranking Style	Q27	1-4			{Q27_1}	{Q27_1.shown}	{Q27_1==3}
S	Short Free Text	Q28				{Q28}	{Q28.shown}	{Q28=='mine'}
Y	Yes/No Radio-Buttons	Q29				{Q29}	{Q29.shown}	{Q29=='Y'}

The reserved 'this', 'self', and 'that' variables

Quite often, you want to evalute all parts of a question, such as counting how many subquestions have been answered, or summing the scores.  Other times, you want to process just certain rows or columns of a question (such as getting the row or column sums and storing them in the database).  These reserved variables make that process relatively painless.

The 'this' variable is used exclusively within the "Whole question validation equation" and "Sub-question validation equation" advanced question options.  It expands to the variable names of each of the cells within those questions.  So, if you want to make sure that each entry is greater than three, you would set the "Sub-question validation equation" to (this > 3).

The 'self' and 'that' variable are more powerful, and serve as macros which are expanded prior to processing equations.  The syntax choices are:

• self
• self.suffix
• self.sub-selector
• self.sub-selector.suffix

suffix is any of the normal qcode suffixes (e.g. NAOK, value, shown)

sub-selector is one of:

• comments - only subquestions that are comments (e.g. from multiple choice with comment and list with comment)
• nocomments - only subquestions that are not comments
• sq_X - where X is a row or column identifier.  Only subquestions matching pattern X are selected. Note that search is done on complete code identifier, then sq_X match and include subquestions nX, X, Xn (e.g. if you use sq_1, subquestions a1, 1a, 1, 11 or 001 was included). Put attention at dual scale question type where subquestions code are QCODE_SQCODE_1 and QCODE_SQCODE_1 and to ranking question type where subquestions code are QCODE_1,QCODE_2 ....

Examples:

• Has any part of a question been answered?  {count(self.NAOK)>0}
• What is the assessment score for this question?  {sum(self.value)}

You can also use these to get row and column totals.  Say you have a array of numbers with rows A-E and columns 1-5.

• What is the grand total?  {sum(self.NAOK)}
• What is the total of row B?  {sum(self.sq_B.NAOK)}
• What is the total of column 3? {sum(self.sq_3.NAOK)}

The 'that' variable is like the 'self' variable, but lets you refer to other questions.  Its syntax is:

• that.qname
• that.qname.suffix
• that.qname.sub-selector
• that.qname.sub-selector.suffix

qname is the question name without any subquestion extensions.  So, say you create a question 'q1', that is its qname

Examples:

• Has any part of question q1 been answered?  {count(that.q1.NAOK)>0}
• What is the assessment score for q2?  {sum(that.q2.NAOK)}
• What is the grand total of q3? {sum(that.q3.NAOK)}
• What is the total of row C in q4?  {sum(that.q4.sq_C.NAOK)}
• What is the total of column 2 in q4? {sum(that.q4.sq_2.NAOK)}

The 'self' and 'that' variables can be used in any relevance,  validation, or tailoring.

The one caveat is that when you use the Show Logic File feature, it will show you the expanded value of 'self' and 'that'.  This lets you see the actual equation that will be generated so that you (and Expression Manager) can validate that the variables exist.  This may seem confusing since you may see quite lenghty equations.  However, if you edit the question, you will see the original equation using 'self' and/or 'that'

Also note that you should not use these variables if (a) you want to explicitly name each variable used in an equation, or (b) use variables that do not have subquestions (e.g. single response questions).  In those cases, prefixing a variable with 'that' is overkill, and you run the risk of getting unexpected results.

Zugriff auf Funktionen

Der Ausdrucksmanager liefert Zugang zu mathematischen, zeichenketten und nutzerdefinierten Funktionen, wie folgend gezeigt. Er hat PHP und JavaScript Äquivalenten für diese Funktionen, sodass diese server- und clientsetig identisch arbeiten. Es ist einfach neue Funktionen hinzuzufügen.

Implementierte Funktionen

Die folgenden Funktionen sind momentan verfügbar:

Function	Meaning	Syntax
abs	Absolute value	number abs(number)
acos	Arc cosine	number acos(number)
addslashes	Quote string with slashes	string addslashes(string)
asin	Arc sine	number asin(number)
atan	Arc tangent	number atan(number)
atan2	Arc tangent of two variables	number atan2(number, number)
ceil	Round fractions up	number ceil(number)
checkdate	Returns true(1) if it is a valid date in gregorian calendar	bool checkdate(month,day,year)
convert_value	Convert a numerical value using a inputTable and outputTable of numerical values	number convert_value(fValue, iStrict, sTranslateFromList, sTranslateToList)
cos	Cosine	number cos(number)
count	count the number of answered (non-blank)questions in the list	number count(arg1, arg12, ..., argN)
countif	Count the number of answered questions in the list equal the first argument	number countif(matches, arg1, arg2, ... argN)
countifop	Count the number of answered questions in the list which pass the criteria (arg op value)	number countifop(op, value, arg1, arg2, ... argN)
date	Format a local date/time	string date(format [, timestamp=time()])
exp	Calculates the exponent of e	number exp(number)
fixnum	Display numbers with comma as radix separator, if needed	string fixnum(number)
floor	Round fractions down	number floor(number)
gmdate	Format a GMT date/time	string gmdate(format [, timestamp=time()])
html_entity_decode	Convert all HTML entities to their applicable characters (always uses ENT_QUOTES and UTF-8)	string html_entity_decode(string)
htmlentities	Convert all applicable characters to HTML entities (always uses ENT_QUOTES and UTF-8)	string htmlentities(string)
expr_mgr_htmlspecialchars	Convert special characters to HTML entities (always uses ENT_QUOTES and UTF-8)	string htmlspecialchars(string)
expr_mgr_htmlspecialchars_decode	Convert special HTML entities back to characters (always uses ENT_QUOTES and UTF-8)	string htmlspecialchars_decode(string)
idate	Format a local time/date as integer	string idate(string [, timestamp=time()])
if	Excel-style if(test,result_if_true,result_if_false)	if(test,result_if_true,result_if_false)
implode	Join array elements with a string	string implode(glue,arg1,arg2,...,argN)
intval	Get the integer value of a variable	int intval(number [, base=10])
is_empty	Determine whether a variable is considered to be empty	bool is_empty(var)
is_float	Finds whether the type of a variable is float	bool is_float(var)
is_int	Find whether the type of a variable is integer	bool is_int(var)
is_nan	Finds whether a value is not a number	bool is_nan(var)
is_null	Finds whether a variable is NULL	bool is_null(var)
is_numeric	Finds whether a variable is a number or a numeric string	bool is_numeric(var)
is_string	Find whether the type of a variable is string	bool is_string(var)
join (New in 2.0 build 130129)	Join elements as a new string	join(arg1, arg2, ... argN)
list	Return comma-separated list of non-blank values	string list(arg1, arg2, ... argN)
log	The logarithm of number to base, if given, or the natural logarithm.	number log(number,base=e)
ltrim	Strip whitespace (or other characters) from the beginning of a string	string ltrim(string [, charlist])
max	Find highest value	number max(arg1, arg2, ... argN)
min	Find lowest value	number min(arg1, arg2, ... argN)
mktime	Get UNIX timestamp for a date (each of the 6 arguments are optional)	number mktime([hour [, minute [, second [, month [, day [, year ]]]]]])
modulo-function	The modulo function is not supported yet. You can use the floor() function instead	floor(x/y)==(x/y)
nl2br	Inserts HTML line breaks before all newlines in a string	string nl2br(string)
number_format	Format a number with grouped thousands	string number_format(number)
pi	Get value of pi	number pi()
pow	Exponential expression	number pow(base, exp)
quoted_printable_decode	Convert a quoted-printable string to an 8 bit string	string quoted_printable_decode(string)
quoted_printable_encode	Convert a 8 bit string to a quoted-printable string	string quoted_printable_encode(string)
quotemeta	Quote meta characters	string quotemeta(string)
rand	Generate a random integer, see this example	int rand() OR int rand(min, max)
regexMatch	compare a string to a regular expression	bool regexMatch(pattern,input)
round	Rounds a number to an optional precision	number round(val [, precision])
rtrim	Strip whitespace (or other characters) from the end of a string	string rtrim(string [, charlist])
sin	Sine	number sin(arg)
sprintf	Return a formatted string	string sprintf(format, arg1, arg2, ... argN)
sqrt	Square root	number sqrt(arg)
stddev	Calculate the Sample Standard Deviation for the list of numbers	number stddev(arg1, arg2, ... argN)
str_pad	Pad a string to a certain length with another string	string str_pad(input, pad_length [, pad_string])
str_repeat	Repeat a string	string str_repeat(input, multiplier)
str_replace	Replace all occurrences of the search string with the replacement string	string str_replace(search, replace, subject)
strcasecmp	Binary safe case-insensitive string comparison	int strcasecmp(str1, str2)
strcmp	Binary safe string comparison	int strcmp(str1, str2)
strip_tags	Strip HTML and PHP tags from a string	string strip_tags(str, allowable_tags)
stripos	Find position of first occurrence of a case-insensitive string	int stripos(haystack, needle [, offset=0])
stripslashes	Un-quotes a quoted string	string stripslashes(string)
stristr	Case-insensitive strstr	string stristr(haystack, needle [, before_needle=false])
strlen	Get string length	int strlen(string)
strpos	Find position of first occurrence of a string	int strpos(haystack, needle [ offset=0])
strrev	Reverse a string	string strrev(string)
strstr	Find first occurrence of a string	string strstr(haystack, needle)
strtolower	Make a string lowercase	string strtolower(string)
strtotime	Parse about any English textual datetime description into a Unix timestamp	int strtotime(string)
strtoupper	Make a string uppercase	string strtoupper(string)
substr	Return part of a string	string substr(string, start [, length])
sum	Calculate the sum of values in an array	number sum(arg1, arg2, ... argN)
sumifop	Sum the values of answered questions in the list which pass the criteria (arg op value)	number sumifop(op, value, arg1, arg2, ... argN)
tan	Tangent	number tan(arg)
time	Return current UNIX timestamp	number time()
trim	Strip whitespace (or other characters) from the beginning and end of a string	string trim(string [, charlist])
ucwords	Uppercase the first character of each word in a string	string ucwords(string)
unique	Returns true if all non-empty responses are unique	boolean unique(arg1, ..., argN)

Geplante Funktionen (oder die zumindest in Betracht gezogen werden)

Andere Funktionen, die geplant (oder die zumindest in Betracht gezogen) sind, aber bis jetzt noch nicht enthalten sind, sind in der folgenden Liste aufgezählt. Einige von diesen sind für die Abwärtskompatibilität mit anderen Umfragetools.

Syntax	Meaning	Comments
e()	returns the value of e
formatDate(X,PAT)	return the string value of date X formatted according to Java data format pattern PAT
formatNumber(X,PAT)	return the string value of number X formatted according to Java number format pattern PAT
getAnsOption(X)	returns the text corresponding to the selected option for answer X	this is the same as X.shown
getAnsOption(X,Y)	returns the text corresponding to the option at index Y of node X
getRelevance(X)	returns the relevance equation for question X
getStartTime()	returns the date corresponding to the system time when the interview was started
getType(X)	returns the string name of the datatype - e.g. *NA* if isNA()
gotoFirst()	jumps to the first relevant set of questions - this violates the normal flow of the system
gotoNext()	jumps to the next set of relevant questions - this violates the normal flow of the system
gotoPrevious()	jumps to the previous set of relevant questions - this violates the normal flow of the system
isAsked(X)	returns true if the answer is neither *NA*, *INVALID*, nor *UNASKED*
isInvalid(X)	returns true if the answer is of type *INVALID*
isNA(X)	returns true if the answer is of type *NA*
isNotUnderstood(X)	returns true if the answer if of type *HUH*
isRefused(X)	returns true if the answer is of type *REFUSED*
isSpecial(X)	returns true if the answer is of type *UNASKED*, *NA*, *REFUSED*, *INVALID*, *UNKNOWN*, or *HUH*
isUnknown(X)	returns true if the answer is of type *UNKNOWN*
jumpTo(X)	jump to the group containing the named question -- this violates the normal flow of the system
jumpToFirstUnasked()	jump to the first unasked question thus bypassing previous answered questions this violates the normal flow of the system
lastIndexOf(X,Y)	returns the last index (base 0) of string Y in string X. Returns -1 if Y is not contained within X
list(X,...)	a string containing a comma separated list of the positive values with "and" separating the last two
mean(X,...)	returns the mean of a list of values
numAnsOptions(X)	returns the number of answer options that question X has
orlist(X,...)	a string containing a comma separated list of the positive values, with "or" separting the last two
parseDate(X,PAT)	returns the date value of string X parsed with Java date format pattern PAT
parseNumber(X,PAT)	returns the numerical value of string X parsed with Java number format pattern PAT
showAllResponsesExcept( questionList,attributeList,attributeTitleList)	questionList = pipe-delimited list of question identifiers; attributeList = pipe-delimited list of attributes (like question#, title, text, type - so you can decide what to show); attributeTitleList = pipe-delimited list of table headers, so can internationalize the report.
showTheseResponses( questionList,attributeList,attributeTitleList)	questionList = pipe-delimited list of question identifiers; attributeList = pipe-delimited list of attributes (like question#, title, text, type - so you can decide what to show); attributeTitleList = pipe-delimited list of table headers, so can internationalize the report.

Der Ausdrucksmanager weiß, welche Variablen lokal sind

Um ordnungsgemäß JavaScript für die Seite zu konstruieren muss der Ausdrucksmanager wissen, welche Variablen auf der Seite gesetzt sind und wie ihre ID ist (e.g. für document.getElementById(x)). Er muss auch wissen, welche Variablen auf anderen Seiten gesetzt sind (sodass sichergestellt werden kann, dass die benötigten <input type='hidden' value='x'> Felder präsent und ausgefüllt sind).

Kaskadierende Bedingungen

Um es genauer zu sagen, wenn eine der Variablen irrelevant ist, wird die gesamte Gleichung irrelevant (false). In der folgenden Tabelle bedeutet N/A zum Beispiel, dass eine der Variablen nicht relevant war.

Operator	Example	a	b	Result
+ (unary)	+a	N/A		false
!	!a	N/A		false
== (or eq)	a == b	N/A	5	false
== (or eq)	a == b	N/A	0	false
== (or eq)	a == b	N/A	N/A	false
!= (or ne)	a != b	N/A	5	false
!= (or ne)	a != b	N/A	N/A	false
!= (or ne)	a != b	N/A	0	false
> (or gt)	a > b	N/A	5	false
>= (or ge)	a >= b	N/A	5	false
< (or lt)	a < b	N/A	5	false
<= (or le)	a <= b	N/A	5	false
and	a and b	N/A	5	false
and	a and b	N/A	N/A	false
or	a or b	N/A	N/A	false
or	a or b	N/A	5	false
+	a + b	N/A	5	false
*	a * b	N/A	5	false
/	a / b	5	N/A	false
()	(a)	N/A		false
(exp)	(a && b)	N/A	5	false
(exp) op (exp)	(b + b) > (a && b)	N/A	5	false
function	sum(a,b,b)	N/A	5	false
function	max(a,b)	N/A	5	false
function	min(a,b)	N/A	5	false
function	implode(', ',a,b,a,b)	N/A	5	false
function	if(a,a,b)	N/A	5	false
function	is_empty(a)	N/A		false
function	is_empty(a)	0 (or blank)		true
function	!is_empty(a)	N/A		false

Überschreiben kaskadierender Bedingungen

Say you want to show a running total of all relevant answers.  You might try to use the equation {sum(q1,q2,q3,...,qN)}.  However, this gets translated internally to LEMif(LEManyNA('q1','q2','q3',...,'qN'),,sum(LEMval('q1'),LEMval('q2'),LEMval('q3'),...,LEMval('qN'))).  So, if any of the values q1-qN are irrelevant, the equation will always return false.  In this case, the sum() will show 0 until all questions are answered.

To get around this, each variable can have a ".NAOK" suffix (meaning that Not Applicable is OK) added to it.  In such cases, the following behavior occurs.  Say you have a variable q1.NAOK

1. q1 is not added to the LEManyNA() clause
2. LEMval('q1') will  continue to check whether the response is relevant, and will return '' if it is not (so individual irrelevant responses will be ignored, but they will not void the entire expression).

Somit ist die Lösung zu dem laufende-Summe-Problem, die Gleichung sum(q1.NAOK,q2.NAOK,q3.NAOK,...,qN.NAOK) zu benutzen.

Die Benutzung des .NAOK Suffixes lässt Autoren auch Umfragen gestalten, die verschiedene mögliche Pfade haben, aber dies kommt später. Zum Beispiel, sagen wir das Subjekt beantwortet die Umfrage in einem Umfang außerhalb des normalen Antwortbereiches. Der Autor könnte das Subjekt benachrichtigen, dass es möglicherweise keine richtigen Ergebnisse bekommen würde und dann fragen ob es so wirklich mit der Umfrage fortfahren wolle. Wenn es Ja sagt, wird der Rest der Fragen gezeigt. Die Bedingungen der restlichen Fragen würden validieren, ob die ersten Antworten in einem normalen Bereich beantwortet wurden, oder ob das Subjekt Ja zu der Frage gesagt hat, die nur dann relevant ist, wenn die anderen Antworten außerhalb des normalen Bereiches lagen.

Wie unterstützt der Ausdrucksmanager Bedingungs-Mikro-Anpassungen?

Hier ist ein Beispiel für Mikro-Anpassungen (der Frage-Typ=='expr' bedeutet Gleichung):

Frage-Nummer	Relevanz	Frage-Typ	Frage
name	1	text	Wie heißen Sie?
age	1	text	Wie alt sind Sie?
badage	age	expr	{(age<16) oder (age>80)}
agestop	badage	message	Sorry, {name}, Sie sind zu {if( (age<16),'jung',if( (age>80),'alt','middle-aged') ) } für diesen Test.
kids	!badage	yesno	Haben Sie Kinder?
parents	1	expr	{!badage && kids=='Y'}
numKids	parents	text	Wie viele Kinder haben Sie?
kid1	parents && numKids >= 1	text	Wie alt ist Ihr erstes Kind?
kid2	parents && numKids >= 2	text	Wie alt ist Ihr zweites Kind?
kid3	parents && numKids >= 3	text	Wie alt ist Ihr drittes Kind?
kid4	parents && numKids >= 4	text	Wie alt ist Ihr viertes Kind?
kid5	parents && numKids >= 5	text	Wie alt ist Ihr fünftes Kind?
sumage	1	expr	{sum(kid1.NAOK,kid2.NAOK,kid3.NAOK,kid4.NAOK,kid5.NAOK)}
report	parents	yesno	{name}, Sie haben behauptet Sie seien {age} und hätten {numKids}.  Die Summe der Alter ihrere ersten {min(numKids,5)} Kinder ist {sumage}

Alle diese Fragen können auf einer einzelnen Seite sein (e.g. in der gleichen Gruppe) und nur relevante Fragen werden angezeigt. Weiterhin, indem sie das Alter der Kinder eintragen wird der sum() Ausdruck in der letzten Frage dynamisch die Seite aktualisieren.

Der Ausdrucksmanager stellt diese Funktionalität zur Verfügung indem jeder Ausdruck mit einem benannten Element eingefasst wird. Jedes mal wenn sich ein Wert verändert, berechnet es den Ausdruck der in dem Element erscheinen sollte neu und aktualisiert die Anzeige. Sie können duzende oder sogar hunderte von solchen zugeschnittenen Elementen auf der gleichen Seite haben und die Seite wird diese wieder innerhalb einer einzigen Bildschirmaktualisierung anzeigen.

Abbildung von LimeSurvey 1.91+ zur Ausdrucksmanager Funktionalität

Old Feature	New Feature	Comments
Conditions	Relevance	You can use very complex conditional equations, and access a broader range of variables
Assessments	Equation	Any assessment scores can be re-structured into an Equation. This both ensures that the score is written to the database, and also lets you see dynamic changes to the score value on the current page
Replacements	Expression Manager	The core engine takes the input string and treats everything within curly braces as an Expression - so it handles all historical replacements types.  To avoid messing up embedded JavaScript, Expression Manager only processes content between curly braces as long as (a)  there is no leading or trailing whitespace within the curly braces - e.g. {expr} is an expression, but { expr}, {expr }, and { expr } are not expressions.  Furthermore, Expression Manager does not process content within its own strings (e.g. {list('hi','there {braces}')} generates "hi there {braces}").  It also ignores escaped curly braces (e.g. \{this is not an expression\})
Validation	Expression Manager	The plan is to take the current min/max Question Attributes and have Expression Manager process them.  That way the min/max values can be expressions themselves

Beziehung zu LimeSurvey Ideen / Feature-Requests

To help with entering and validating expressions, EM provides syntax highlighting with the following features:

Types and Meanings of Syntax Highlighting

Color	Sample	Meaning	Tooltip	Comments
tan background	Sample	the whole equation	none	Anything within curly braces that is recognized as an equation (e.g. there is no leading or trailing whitepace) will be color-coded with a tan background to help distinguish it from surrounding text
blue bold text	Sample	function name	meaning and allowable syntax	function names, or things that should be functions since they are followed by an opening parenthesis, are presented in bold blue text. Tooltips show the meaning and allowable syntax for the function.
grey text	Sample	string	none	single and double-quoted strings are shown in grey text
bold maroon text	Sample	variable set on the same page, but after the current question	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on the same page but after the current question is shown in bold maroon text. This color coding should alert authors to possible errors in question sequencing; but it is allowed since some authors may want this sequence of variables a page, especially for dynamic reports. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold cyan text	Sample	variable set on the same page, prior to the current question	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on the same page and prior to the current question is shown in bold cyan text. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold green text	Sample	variable set on a prior page	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on a prior page is shown in bold green text. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold pink text	Sample	variable set on a later page	[name or SGQA code]: question; value; answerList showing codes for each value	Any variable that is set on a prior page is shown in bold pink text. These are erorrs since the variable is being used before it is declareed. The tooltip shows its name (if you used INSERTANS:xxx) or SGQA code (if you used the new naming system), the actual question, and its current value (or blank if not set). If the question type expects responses from an enumerated value set, the mapping of the codes to display values is show.
bold tan text	Sample	a lime replacement value	the value	Lime Replacement Strings (like {TOKEN:xxx}, {PRIVACY_MESSAGE}) are shown in bold tan text.
red text	Sample	assignment operator	warning message	If you use one of the assignment operator (=) that operator will be displayed in red text. This is meant to help prevent accidental re-assignment of values when you really meant to check whether a == b instead of setting the value of a = b.
normal black text	Sample	punctuation	none	All other punctuation within the expression is shown as normal black text.
red-boxed text	a bold red line surrounds the error	syntax error	description of the error	Any detected syntax errors are shown by surrounding the error with a red box. The tooltip shows the error. Examples include unmatched parentheses, use of undefined functions, passing the wrong number of arguments to functions, poorly structured expressions (e.g. missing operators between variables), trying to assign a new value to a read-only variable, trying to assign values to non-variables, or using unsupported syntax. Note that the syntax error dectection system may only report one error in an expression even if there are multiple errors; however, if any errors are detected, at least one error will be shown.