# Error defining relationships implementing interfaces in GraphQL Library

**URL:** <https://community.neo4j.com/t/error-defining-relationships-implementing-interfaces-in-graphql-library/60085>\
**Category:** Neo4j Graph Platform\
**Tags:** migrated\
**Created:** [July 18, 2022, 12:03pm UTC](https://community.neo4j.com/t/error-defining-relationships-implementing-interfaces-in-graphql-library/60085 "2022-07-18T12:03:12Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![AdrianSpear](https://avatars.discourse-cdn.com/v4/letter/a/3d9bf3/32.png) [@AdrianSpear](https://community.neo4j.com/u/AdrianSpear)\
**Post date:** [July 18, 2022, 12:03pm UTC](https://community.neo4j.com/t/error-defining-relationships-implementing-interfaces-in-graphql-library/60085/1 "2022-07-18T12:03:12Z")

</div>

Hi,

Using following definitions:

interface IGraphEdge @relationshipProperties {

```
created: DateTime! @timestamp(operations: \[CREATE\])  

modified: DateTime! @timestamp(operations: \[CREATE, UPDATE\])  

```

}

interface IPerson {

```
displayName: String!  

knows: \[IPerson!\]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")  

```

}

type Employee implements IPerson {

```
displayName: String!  

knows: \[IPerson!\]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")  

```

}

type Contractor implements IPerson {

```
displayName: String!  

knows: \[IPerson!\]! @relationship(type: "KNOWS", direction: OUT, properties: "IGraphEdge")  

```

}

Yields the following error:

Error: Input Object type IGraphEdgeCreateInput must define one or more fields.

Input Object type IGraphEdgeUpdateInput must define one or more fields.

Adding a field to the IGraphEdge resolves the issue but is not required - I only require the created and modified date times on my basic edges.

interface IGraphEdge @relationshipProperties {

```
created: DateTime! @timestamp(operations: \[CREATE\])  

modified: DateTime! @timestamp(operations: \[CREATE, UPDATE\])  

creator: String!  

modifier: String!  

```

}

What am I missing here?