A workflow is a collection of blocks that executes a set of commands to collect, process and display data.  All workflows are composed of at least one container block, with at least one other block placed within it.  

The animation below shows how a workflow can be created from snapping blocks together.

Building a Basic Workflow

TABLE OF CONTENTS

• Connecting blocks together to form a workflow
• Step 1: Start with a container block
• Step 2: Select your area of interest (AOI)
• Step 3: Select a time period
• Step 4: Collate your data into time periods
• Step 5: Finally, add an output block
• Step 6: Check for errors
• Step 7: Run the workflow
• Step 8: View the output on the map

Connecting blocks together to form a workflow

• As described in the Toolbox article, the most basic workflow requires at least one container block and one or more standard blocks that sit within the container.
• Drag and drop these blocks from the Toolbox into the Workspace.
• Drag one block close to another so that the notches meet.
• Once they connect you will hear a "click" (if your volume is up), and the block will be highlighted.
• If the blocks will not connect, or it is automatically moved out of the way, then these blocks are unable to be connected.
• The following steps describe how to connect some blocks together to create a basic workflow.  

Step 1: Start with a Use this dataset container block

• Within the INPUT> Dataset section of the Toolbox you will find a container block called Use This Dataset. Drag it into the workspace. 
• Click on the Search Datasets window to open the data catalogue and then choose a dataset to work with. 
• For this example, choose the Sentinel 2 dataset. 
• Notice that there is a Run button at the bottom of this container block.  That will allow you to run just this workflow and nothing else within the workspace.
• If you leave the Add Recommended Blocks checkbox checked, the following blocks will be added for you.

Step 2: Select your area of interest (AOI)

• If you unchecked the Add Recommended Blocks option on the data, you will have to add these blocks by hand. 
• Within the INPUT>Areas  section of the Toolbox, you will find a block called Select Area of Interest. Drag it into the workspace.
• Now drag that block to the container block and align the notches, then drop the block in place.
• You will hear a "click", and the block will be highlighted, once they connect.
• Note that you will see the space highlighted when it is time to drop the block in place.
• If you have already followed the instructions about choosing an area of interest on the map then this will appear in the drop-down menu.
• If there are no areas to select from, then quickly draw a rectangle on the map by selecting the drawing tool at the top of the map.  It will automatically be assigned as Area 1 and appear in the AOI block. 

Step 3: Select a time period

• Within the INPUT> Time section of the Toolbox, you will find a block called Select Time Period. Drag it into the workspace.
• Now drag that block to the container block and align the notches below the Select Area of Interest block, then drop the block in place.
• You will hear a "click", and the block will be highlighted, once they connect.
• Note that these two blocks are interchangeable -- they do not need to be in this order.
• Use the date picker to select a start and end time.  For this example, choose a period of a few months. 
• Note that these dates default to the range over which the data selected is available.  For example, if you choose Sentinel 2, it starts on 28th March 2017.  Whereas, if you choose Sentinel 1 it switches to 3rd October 2014.

Step 4: Collate your data into time periods

• Within the INPUT>Combine section of the Toolbox, you will find a block called Aggregate Images in Time.  Drag it into the workspace.
• Now drag that block to the container block and align the notches below the other internal blocks and drop the block in place just as you did with the other blocks. 
• This is a unique block that stitches all the parts of the dataset together and groups them in time.  You will find a detailed description of how to use this block in the How to Combine Your Data Effectively article.
• For now, just select, Over the entire time period, and Median.

Step 5: Finally, add an output block

• You will find a block called Add to Map within the OUTPUT>Map Layer section of the Toolbox.  Drag it into the workspace.
• Now drag that block to the container block and align the notches below the Combine Images in Time block and drop the block in place.
• The block will show dropdown menus for three colour bands: R, G, and B. These are the output colour channels to display the image and as default for Sentinel 2 will be set to the red, green and blue channels of the Sentinel 2 instrument.
• If you leave these default options for RGB you will get a real colour image, since it assigns red to R, green to G, and blue to B.  If you change these to R:nir, G:red and B:green, you will get a false colour image that highlights healthy vegetation as red in the image.
• By selecting the options icon you will be able to adjust how the data appears.

Step 6: Check for errors

• If a red triangle appears,  you are not yet ready to run the workflow.

• Click on the red triangle and a text bubble will appear telling you what you are missing. This may be that the dates are incompatible with the data selection, or you still need to add a necessary block to make the workflow run. 
• Follow the guidance in the text bubble.

Step 7: Run the workflow

• Click on the RUN WORKFLOW button to run the workflow.

• You can press the red stop button if you want to halt the process before it has finished running. 

Step 8: View the output on the map

• Now you need to look at the output on the map. 

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