I worked on a flex application 6-7 months back. We used flex 3.5 sdk.

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Asked: May 22, 20262026-05-22T11:30:37+00:00 2026-05-22T11:30:37+00:00

I worked on a flex application 6-7 months back. We used flex 3.5 sdk. Now we are upgrading our flex app with flex sdk 4/4.1

I am still new to flex development and I have a very basic question related to namespace.

I have seen three different namespaces in flex sample applications. What is the purpose of having three diff namespaces? When do I use each of them ?

xmlns:fx="http://ns.adobe.com/mxml/2009" 
xmlns:s="library://ns.adobe.com/flex/spark" 
xmlns:mx="library://ns.adobe.com/flex/mx"

Thanks

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Editorial Team · Answer 1 · 2026-05-22T11:30:37+00:00

Namespaces are a way of logically grouping code together. Here’s some more on that from Adobe.

In your particular example, these are XML Namespaces.

The particular namespaces listed above are listed as they are being used by your Flex application for:

fx – Contains the top-level ActionScript Language elements.

s – Include the Flex Spark components

mx – Contains all the components in the Flex mx.* packages, flex charting & data visualization components.

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