It defines a simple service (searchProductsByGoodIdentificationValue) with verb POST that can be accessed via a REST URL.

<service name="searchProductsByGoodIdentificationValue" engine="java" transaction-timeout="7200" verb="post" export="true"
             location="org.apache.ofbiz.api.demo.RestDemoServices" invoke="searchProductsByGoodIdentificationValue" auth="true">
       <description>Search Products by Good Identification Value</description>
       <attribute name="idFragment" type="String"  mode="IN" optional="false"></attribute>
       <attribute name="products" type="java.util.ArrayList" mode="OUT" optional="true"/>
</service>

In Order to Call this service via REST :

POST https://localhost:8443/rest/services/searchProductsByGoodIdentificationValue
Content-Type: application/json
Authorization: Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzUxMiJ9.eyJpc3MiOiJBcGFjaGVPRkJpeiIsImlhdCI6MTU0NzczOTM0OCwiZXhwIjoxNjc5Mjc1MzQ4LCJhdWQiOiJ3d3cuZXhhbXBsZS5jb20iLCJzdWIiOiJqcm9ja2V0QGV4YW1wbGUuY29tIiwiR2l2ZW5OYW1lIjoiSm9obm55IiwiU3VybmFtZSI6IlJvY2tldCIsIkVtYWlsIjoianJvY2tldEBleGFtcGxlLmNvbSIsInVzZXJMb2dpbklkIjoiYWRtaW4iLCJSb2xlIjpbIk1hbmFnZXIiLCJQcm9qZWN0IEFkbWluaXN0cmF0b3IiXX0.fwafgrgpodBJcXxNTQdZknKeWKb3sDOsQrcR2vcRw97FznD6mkE79p10Tu7cqpUx7LiXuROUAnXEgqDice-BSg
{
    "idFragment": "2644"
}

Response

{
  "statusCode" : 200,
  "statusDescription" : "OK",
  "data" : {
    "products" : [ {
      "internalName" : "Round Gizmo",
      "productId" : "GZ-2644",
      "primaryProductCategoryId" : "101",
      "isVariant" : "N",
      "goodIdentificationTypeId" : "INVOICE_EXPORT",
      "idValue" : "GZ-2644-replaced",
      "isVirtual" : "N"
    } ]
  }
}