Error in Model AppML

I'm trying to learn AppML, for prototyping and maybe use in production.

But I face the following error: Error in Model: task_model

I have a model_tarefas.js file in to date with the following content:

{
    "rowsperpage" : 10,
    "database" : {
        "connection" : "dbtarefas",
        "sql" : "SELECT id, descricao, finalizado, data_finalizado FROM tarefas",
        "orderby" : "id"
    }
}

The same is in agreement with the small existing documentation.

Inside the main section I have the code:

<section class="w3-container" appml-data="data/appml.php?model=model_tarefas">

When I use a local variable as a data source, it works fine, but when I call the database, it gives me a problem.