In this example, we will create a new domain entity called Student Transportation. This entity will be exposed in Ed-Fi ODS / API through a new API resource called studentTransportations. 

Before you begin:

• This example uses MetaEd to generate extended artifacts and documentation. MetaEd is a free tool developed by the Ed-Fi Alliance, and is the recommended way to add new fields to the Ed-Fi ODS / API. You should download and install MetaEd before beginning. This example goes step-by-step, so it's okay if you've never used MetaEd before. If you prefer to generate extended artifacts manually instead of using MetaEd, steps are listed in Appendix A of this page.
• This example assumes that the Ed-Fi ODS / API has been successfully downloaded and is running in a local development environment per the instructions in the Getting Started documentation.
• Back up any existing code or scripts, either in source control or on your file system. This is important if you or your team have performed these steps before. The MetaEd deployment feature replaces existing files, some of which may contain hand-crafted customizations (e.g., to define an authorization strategy).

The steps can be summarized as:

Each step is outlined in detail, below. 

Step 1. Design Your Extension

In a real project, you would take the preliminary step of designing your extension. We'll propose a design.

This example will create a new Student Transportation entity. The ODS / API data model has elements related to transportation (such as a School entity and a Student entity), but there is no means to store student bus assignments, or the distance from a student's home to school. We'll add those in our new entity, and relate our new entity to existing parts of the data model.

The following is a diagram is a sketch showing the new Student Transportation entity (on the left), along with its properties. Our new entity relates to School and Student, entities which are already present in the ODS / API data model. These existing entities are shown in gray (on the right).This example is simple, but illustrates most of the essential concepts required to extend the Ed-Fi ODS / API. Let's continue with the mechanics.

Step 2. Author Your Extension Using MetaEd

In this step, we'll create a new project in MetaEd, and author our new entity. It's easy — but you do need to download and install MetaEd to do this step. Do that now if you haven't already.

Step 2a. Set or Confirm MetaEd Target Version

MetaEd allows you to target different versions of the Ed-Fi technology stack and data model. Confirm that your MetaEd IDE is targeting v6.1 by following the instructions in the Version Targeting documentation for the MetaEd IDE.

The desired model for the latest ODS / API is "ed-fi-model-4.0a".

Step 2b. Create a New Extension Project

Create a new extension by following the steps in MetaEd IDE - Creating and Maintaining Your Extension. For this example, place your extension in a folder called "StudentTransportation".

Step 2c. Update the package.json File

Open the package.json file by double-clicking on the file in the tree view to the left and provide an appropriate name for your project. In this case we will call it "SampleStudentTransportation".

Click File > Save (Ctrl + S) to save your changes.

Step 2d. Add a Domain Entity File to Your Project

We're going to add a Domain Entity source file to the project we just created. Note that MetaEd files are required to be organized into subfolders. Folders are generally named after their entity type. When you followed the steps in MetaEd IDE - Creating and Maintaining Your Extension one of the folders you created was called "DomainEntity". We will now add a MetaEd source file to that folder. 

Right-click on the folder DomainEntity, and select New File.

Name the new file StudentTransportation.metaed to match the name of the new entity to be created.

Note the new file appears in the tree view to the left. Double-click on the file in the tree view to open it. 

Step 2e. Author and Save Your Extension

Type or copy and paste the code listing below into your MetaEd file:

    
Domain Entity StudentTransportation
documentation "StudentTransportation"
domain entity EdFi.School
    documentation "The school to and from which the student is being transported."
    is part of identity
domain entity EdFi.Student
    documentation "The student being transported."
    is part of identity
string AMBusNumber
    documentation "The bus that delivers the student to the school in the morning."
    is part of identity
    max length 6
string PMBusNumber
    documentation "The bus that delivers the student home in the afternoon."
    is part of identity
    max length 6
decimal EstimatedMilesFromSchool
    documentation "The estimated distance, in miles, the student lives from the school."
    is required
    total digits 5
    decimal places 2

If you want to bulk load this extension, you need to create an interchange file. Right-click on the Interchange folder, select New File. Name your file StudentTransportation.metaed. Replace the template text in your new Interchange source file with the following code:

Interchange StudentTransportation
    documentation "StudentTransportation"
    extended documentation "StudentTransportation"
    use case documentation "StudentTransportation"
    domain entity StudentTransportation

Click File > Save (Ctrl + S) to save your changes.

Step 3. Generate Extended Technical Artifacts Using MetaEd

In this step, we'll build our new MetaEd project. This is fairly straightforward.

Step 3a. Build Your Project

Click Build in the VSCode Editor to generate artifacts.

Artifacts build successfully. Note that you may have to refresh the Explorer tree to see the MetaEd Output

Step 3b. View MetaEd Output

You can expand the project in the tree view and click "MetaEdOutput" to explore generated artifacts. The artifacts include technical output such as SQL scripts, API metadata, and XSD used by the code generation, but also updated documentation such as data dictionaries that add your extension definitions to the ODS / API documentation.

We'll look at how to use this MetaEd output in your code below. First, we'll need to set up our extension project in Visual Studio.

Step 4. Create Extension Project in ODS / API Solution

This step will create the C# Extension files necessary to build your extended solution. This step assumes you've successfully downloaded and can run the ODS / API in a local development environment per the instructions in the Getting Started documentation. Do that now if you haven't already.

Step 4a. Set Up the C# Project Template

Visual Studio Project Templates can be installed by following steps in Project Templates Installation section of this documentation.

Step 4b. Create new Extension Project

4b.1. To add a project to your Ed-Fi-Ods Visual Studio Solution, right-click on the Ed-Fi Extensions Folder. Select Add > New Project.

4b.2. Search and select the Ed-Fi API Extensions Project Template option and click Next. 

In the Project Name field enter EdFi.Ods.Extensions.SampleStudentTransportation and click Create.

Step 4c. Rename the "Marker" Interface file

4c.1. Right-click on the EdFi.Ods.Extensions.ExtensionName.nuspec file in newly created EdFi.Ods.Extensions.SampleStudentTransportation project and Rename the file to EdFi.Ods.Extensions.SampleStudentTransportation.nuspec.

Right-click on the Marker_EdFi_Ods_Extensions_ExtensionName.cs file and Rename the file to Marker_EdFi_Ods_Extensions_SampleStudentTransportation.cs.

4c.2. When prompted choose to rename all references to the code element Marker_EdFi_Ods_Extensions_ExtensionName.

Step 4d. Integrate Extension into the Solution

In this step, we'll integrate the extension into the solution.

4d.1. Locate the EdFi.Ods.WebApi project, within the "Entry Points" folder. Right-click, select Add > Project Reference..., then select the EdFi.Ods.Extensions.SampleStudentTransportation project.

4d.2. Locate any profile projects in the solution. Right-click, select Add > Project Reference..., then select the EdFi.Ods.Extensions.SampleStudentTransportation project. This step is needed only if any of the Profile resources in the Profiles.xml document are extended, or extension entities are being constrained by a particular Profile. 

Step 5. Deploy your Extended Artifacts to the ODS / API Solution

In this step, we'll use the MetaEd "Deploy" feature and integrate the files you've generated with the ODS / API Solution. The MetaEd IDE can deploy the generated artifacts necessary for an ODS / API build of an extension project. These include the generated SQL, generated XSD, and other material.

You can easily configure the MetaEd IDE to copy the generated files to the correct locations for the ODS / API project.

Step 5a. Confirm MetaEd Deployment Settings

Ensure that your Ed-Fi ODS / API source directory is set properly in the MetaEd Extension settings. In VS Code open Settings Ctrl+, and switch to the Workspace tab, find the MetaEd extension and update the "Ods Api Deployment Directory" to point to the folder that contains the Ed-Fi-ODS and Ed-Fi-ODS-Implementation folders.

Step 5b. Deploy Your Extended Artifacts

Deploy by clicking Deploy on the VSCode menu

This will run a new build of all artifacts, and the artifacts required for your Extended ODS / API project will be copied over to the correct locations. For instructions on how to perform the steps manually, see Appendix A, below.

Step 6. Configure Security

The Ed-Fi ODS / API is secure by default. One implication of this design principle is that new entities and elements may not be accessed until an authorization strategy is applied. This prevents accidental release of confidential information, but does require active steps on the part of system developers to enable access to Extensions.

Create a security SQL script called 0001-StudentTransportation_ResourceClaims.sql and place it in the Ed-Fi-ODS-Implementation/Application/ EdFi.Ods.Extensions.SampleStudentTransportation/Artifacts/MsSql/Data/Security folder (Create 'Security' folder if it does not exist). Copy the contents of the following SQL DML script into the newly created file and save.

DECLARE @ApplicationId INT

SELECT @ApplicationId = ApplicationId
FROM [dbo].[Applications]
WHERE ApplicationName = 'Ed-Fi ODS API'
 
DECLARE @ParentResourceClaimId INT
SELECT @ParentResourceClaimId = ResourceClaimId
FROM [dbo].[ResourceClaims]
WHERE ResourceName = 'relationshipBasedData'

INSERT INTO [dbo].[ResourceClaims] ( [DisplayName]
                                     ,[ResourceName]
                                     ,[ClaimName]      
                                     ,[ParentResourceClaimId]
                                     ,[Application_ApplicationId]
                                     )
VALUES ('studentTransportation'
        ,'studentTransportation'
        ,'http://ed-fi.org/ods/identity/claims/sample-student-transportation/studentTransportation'
        ,@ParentResourceClaimId
        ,@ApplicationId
        )

Preventing Resource Name Conflicts

With MetaEd 2+, it is possible to create extension resources that use the same name as an Ed-Fi standard resource. The authorization metadata supports this through a change in behavior so it no longer uses just the resource name to identify the resource, but instead uses the ClaimName. To prevent possible naming conflicts, the claim name's URI value should include the schema representation, using the following format:

http://ed-fi.org/ods/identity/claims/{schema}/{resourceName}

The URI representation of the schema name should be derived by splitting the terms in the name of the extension, inserting hyphens and converting to lower case. For example, "SampleStudentTransportation" would be separated into "Sample", "Student" and "Transportation" and then combined with hyphens and converted to lower case as "sample-student-transportation".

The resource name should be the camel-cased (also known as "medial capitals"), singularized name of the resource (e.g., "studentTransportation" not "StudentTransportation" or "studentTransportations").

Note that in 0001-StudentTransportation_ResourceClaims.sql script above, the resulting ClaimName value is "http://ed-fi.org/ods/identity/claims/sample-student-transportation/studentTransportation".

Step 7. Run Code Generation and Verify Changes 

Save all modified files, close Ed-Fi-ODS.sln, and re-run the code generation steps outlined in the Getting Started Guide (i.e., from a PowerShell prompt run Initialize-PowershellForDevelopment.ps script, followed by the initdev command). Then, run the application and view the Ed-Fi ODS / API in the Swagger UI. The following new API resource should be visible:

Next Steps & Further Information

Congratulations, you've successfully extended an instance of the Ed-Fi ODS / API. The Ed-Fi Extension in this example is fairly simple. It's a good place to start, but most enterprise users have more complicated needs. The following links are useful for developing more complex extensions and getting the development work into production.

• Student Transcript Extension Example. Working through this example is a great next step if you want to move on to more complicated extension scenarios.
• The MetaEd Cookbook. This documentation provides excellent examples of common scenarios, from the simple to very complex.

Appendix A: Adding Manually Created Extensions

Step 1. Set Up the C# Project Template

Visual Studio Project Templates can be installed by following steps in Project Templates Installation section of this documentation.

Step 2. Create new Extension Project

2.1. To add a project to your Ed-Fi-Ods Visual Studio Solution, right-click on the Ed-Fi Extensions Folder. Select Add > New Project.

2.2. Search and select the Ed-Fi API Extensions Project Template option and click Next. 

In the Project Name field, enter EdFi.Ods.Extensions.SampleStudentTransportation and click Create.

Step 3. Rename the "Marker" Interface File

3.1.  Right-click on the EdFi.Ods.Extensions.ExtensionName.nuspec file in newly created EdFi.Ods.Extensions.SampleStudentTransportation project and Rename the file to EdFi.Ods.Extensions.SampleStudentTransportation.nuspec.

Right-click on the Marker_EdFi_Ods_Extensions_ExtensionName.cs file and Rename the file to Marker_EdFi_Ods_Extensions_SampleStudentTransportation.cs.

3.2. When prompted choose to rename all references to the code element Marker_EdFi_Ods_Extensions_SampleStudentTransportation.

Step 4. Integrate Extension into the Solution

In this step, we'll integrate the extension into the solution.

4.1. Locate the EdFi.Ods.WebApi project, within the "Entry Points" folder. Right-click, select Add > Project Reference..., then select the EdFi.Ods.Extensions.SampleStudentTransportation project.

4.2. Locate any profile projects in the solution. Right-click, select Add > Project Reference..., then select the EdFi.Ods.Extensions.SampleStudentTransportation project. This step is needed only if any of the Profile resources in the Profiles.xml document are extended, or extension entities are being constrained by a particular Profile. 

Step 5. Add Extension Metadata

The code listings in this section use the sample extension material from Ed-Fi-ODS/Samples/Extensions/StudentTransportation.

5.1. Map Artifacts

• Copy the metadata files to the implementation project.

xcopy /y "Ed-Fi-ODS\Samples\Extensions\StudentTransportation\StudentTransportationMetaEd\MetaEdOutput\samplestudenttransportation\Database\SQLServer\ODS\Structure" "Ed-Fi-ODS-Implementation\Application\EdFi.Ods.Extensions.SampleStudentTransportation\Artifacts\MsSql\Structure\Ods\*"
  
xcopy /y "Ed-Fi-ODS\Samples\Extensions\StudentTransportation\StudentTransportationMetaEd\MetaEdOutput\samplestudenttransportation\Database\PostgreSQL\ODS\Structure" "Ed-Fi-ODS-Implementation\Application\EdFi.Ods.Extensions.SampleStudentTransportation\Artifacts\PgSql\Structure\Ods\*"

xcopy /y "Ed-Fi-ODS\Samples\Extensions\StudentTransportation\StudentTransportationMetaEd\MetaEdOutput\samplestudenttransportation\ApiMetadata" "Ed-Fi-ODS-Implementation\Application\EdFi.Ods.Extensions.SampleStudentTransportation\Artifacts\Metadata\*"
  
xcopy /y "Ed-Fi-ODS\Samples\Extensions\StudentTransportation\StudentTransportationMetaEd\MetaEdOutput\samplestudenttransportation\XSD" "Ed-Fi-ODS-Implementation\Application\EdFi.Ods.Extensions.SampleStudentTransportation\Artifacts\Schemas\*"
  
xcopy /y "Ed-Fi-ODS\Samples\Extensions\StudentTransportation\StudentTransportationMetaEd\MetaEdOutput\samplestudenttransportation\Interchange" "Ed-Fi-ODS-Implementation\Application\EdFi.Ods.Extensions.SampleStudentTransportation\Artifacts\Schemas\*"

Step 6. Configure Security

The Ed-Fi ODS / API is secure by default. One implication of this design principle is that new entities and elements may not be accessed until an authorization strategy is applied. This prevents accidental release of confidential information, but does require active steps on the part of system developers to enable access to Extensions.

Create a security SQL script called 0001-StudentTransportation_ResourceClaims.sql and place it in the Ed-Fi-ODS-Implementation/Application/ EdFi.Ods.Extensions.SampleStudentTransportation/Artifacts/MsSql/Data/Security folder (Create 'Security' folder if it does not exist). Copy the contents of the following SQL DML script into the newly created file and save.

DECLARE @ApplicationId INT

SELECT @ApplicationId = ApplicationId
FROM [dbo].[Applications]
WHERE ApplicationName = 'Ed-Fi ODS API'
 
DECLARE @ParentResourceClaimId INT
SELECT @ParentResourceClaimId = ResourceClaimId
FROM [dbo].[ResourceClaims]
WHERE ResourceName = 'relationshipBasedData'

INSERT INTO [dbo].[ResourceClaims] ( [DisplayName]
                                     ,[ResourceName]
                                     ,[ClaimName]      
                                     ,[ParentResourceClaimId]
                                     ,[Application_ApplicationId]
                                     )
VALUES ('studentTransportation'
        ,'studentTransportation'
        ,'http://ed-fi.org/ods/identity/claims/sample-student-transportation/studentTransportation'
        ,@ParentResourceClaimId
        ,@ApplicationId
        )

Step 7. Run Initdev

Save all modified files, close Ed-Fi-ODS.sln, and re-run the code generation steps outlined in the Getting Started Guide (i.e., from a PowerShell prompt run Initialize-PowershellForDevelopment.ps script, followed by the initdev command). Then, run the application and view the Ed-Fi ODS / API in the Swagger UI. The following new API resource should be visible: