# Skip Logic {#skip-logic} Skip Logic controls **whether a question is shown**. A question with skip logic only appears when its conditions are met. This is different from [Validation](/user-manual/validation.md), which controls whether an *entered answer* is acceptable — a question hidden by skip logic is simply not presented at all. In the underlying survey schema, skip logic is stored as the **`relevant`** field. In the designer, you configure it through **Skip Logic**. --- ## Where to configure it {#where-to-configure-it} 1. Open your survey in the **Survey Designer**. 2. Select the question in the canvas. 3. In the right-hand **Properties** panel, scroll to the **Advanced** section. 4. Click **Skip Logic**. The **Skip Logic Builder** opens with two tabs: - **Visual Builder** — add conditions ("when `age` is greater than or equal to 18"), combine them with **AND** / **OR**, and nest groups of conditions. - **Raw Expression** — type the expression directly in a client-friendly format (see below). The generated XPath expression is shown as you build, and it is validated against the server when you save. Questions with no conditions are always shown. > **Scope rule:** A question inside a group can only reference questions in its > **same group** plus **top-level** questions. A top-level question cannot > reference a question inside a group. This keeps skip logic predictable. --- ## The two expression formats {#the-two-expression-formats} ### Raw expression (what you type) {#raw-expression-what-you-type} The Raw Expression tab uses a compact, client-friendly format: ```text age >= 18 & has_children = Yes ``` - `&` means **AND** - `|` means **OR** - Values with spaces do not need quotes - Use parentheses for grouping: `facility_type=Primary Health Centre&(region=North|region=South)` ### Internal format (what is stored) {#internal-format-what-is-stored} The builder converts what you type into the internal XPath format that is stored with the question and evaluated at runtime: ```text ${age} >= 18 and ${has_children} = 'Yes' ``` You will see the internal format in the **Generated Expression** preview. If you paste an existing XLSForm expression (the internal format), the builder parses it back into the visual builder automatically. --- ## Simple equality {#simple-equality} Show pregnancy questions only when the respondent's sex is female: ```text ${sex} = 'female' ``` In the raw tab, the same rule reads `sex = female`. ## Multiple conditions {#multiple-conditions} ### AND — all conditions must be true {#and--all-conditions-must-be-true} Show questions only when the respondent is female **and** of age: ```text ${sex} = 'female' and ${age} >= 18 ``` ### OR — any condition may be true {#or--any-condition-may-be-true} Show a section when either condition holds: ```text ${district} = 'Mumbai' or ${district} = 'Pune' ``` ### Mixed AND / OR with parentheses {#mixed-and--or-with-parentheses} ```text (${sex} = 'female' or ${sex} = 'trans_female') and ${age} >= 18 ``` ## Numeric conditions {#numeric-conditions} Show adult employment questions when age is 18 or older: ```text ${age} >= 18 ``` All comparison operators are available: `=`, `!=`, `<`, `<=`, `>`, `>=`. ## Select-one questions {#select-one-questions} Show a "Specify other" question when **Other** is selected: ```text ${employer_type} = 'other' ``` For a select-one, a simple equality works because exactly one option is chosen. ## Select-multiple questions {#select-multiple-questions} For multi-select questions, use `selected()` to test a single option: ```text selected(${symptoms}, 'fever') ``` and `count-selected()` for the number of selected options: ```text count-selected(${symptoms}) >= 2 ``` > Note: `selected()` requires the option value (the variable name of the > choice), not the displayed label. ## Nested skip logic {#nested-skip-logic} Skip logic chains naturally. Question C can depend on Question B, which depends on Question A: ```text # Question A (no skip logic) — always shown # Question B shown only when: ${consent} = 'yes' # Question C shown only when BOTH: ${consent} = 'yes' and ${married} = 'yes' ``` When the answer that Question C depends on (e.g. consent) changes, MQUAD re-evaluates C's visibility immediately. Hiding a question does **not** erase an answer already entered for it — the value is retained (and re-shown if the question becomes visible again). If you need a hidden value to be cleared, add validation on the hidden question, or clear it by hand before submission. ## Date-based skip logic {#date-based-skip-logic} Calculations and date functions are valid inside relevance expressions: ```text date-diff('days', ${registration_date}, ${visit_date}) >= 30 ``` Show the follow-up section when at least 30 days have passed since registration. See [Date and Time Reference](/user-manual/date-time-reference.md) for the exact rules of `date-diff`. ## Calculated-value-driven skip logic {#calculated-value-driven-skip-logic} Skip logic can depend on a **calculated** value: ```text ${age} >= 18 ``` where `age` is itself a calculated question: ```text age(${dob}, ${interview_date}) ``` MQUAD's dependency graph re-evaluates calculations first, then re-evaluates relevance expressions that depend on them, so the section appears as soon as the age computation updates. See [Auto-Populate and Calculations](/user-manual/calculation-expressions.md). --- ## Common mistakes {#common-mistakes} - **Using the label instead of the variable name** — `sex = 'female'` uses the variable name, not the displayed question text. - **Missing quotes on string values** — `district = Mumbai` may parse but won't match; use `district = Mumbai` in the raw tab (unquoted is accepted there) or `'Mumbai'` in the internal format. - **Testing a multi-select with `=`** — a multi-select value can contain many options, so `symptoms = 'fever'` only matches when *fever is the only* selection. Use `selected(${symptoms}, 'fever')` instead. - **Referencing a sibling-group question** — questions inside a group can only reference same-group and top-level questions. Move the referenced question to the top level if needed.