Android - What does question mark signify in searchable.xml?
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I'm debugging **SearchableDictionary sample on android 4.0**. In searchable.xml, what does question mark signify in this attribute, `android:searchSuggestSelection=" ?"`? 

Here is the snippet : 

    <searchable xmlns:android="http://schemas.android.com/apk/res/android"
        android:label="@string/search_label"
        android:hint="@string/search_hint"
        android:searchSettingsDescription="@string/settings_description"
        android:searchSuggestAuthority="com.example.android.searchabledict.DictionaryProvider"
        android:searchSuggestIntentAction="android.intent.action.VIEW"
        android:searchSuggestIntentData="content://com.example.android.searchabledict.DictionaryProvider/dictionary"
        android:searchSuggestSelection=" ?"   
        android:searchSuggestThreshold="1"
        android:includeInGlobalSearch="true"
        >
 </searchable>

Thanks.