old_contents: // Article schema
  
  var ArticleSchema = new Schema({
    title       : {type : String, default : '', trim : true},
    body        : {type : String, default : '', trim : true},
    created_at  : {type : Date, default : Date.now},
    updated_at  : {type : Date, default : Date.now}
  });
  
  ArticleSchema.path('title').validate(function (title) {
    return title.length > 0;
  }, 'Article title cannot be blank');
  
  ArticleSchema.path('body').validate(function (body) {
    return body.length > 0;
  }, 'Article body cannot be blank');
  
  
  mongoose.model('Article', ArticleSchema);
  
new_contents: // Article schema
  
  var ArticleSchema = new Schema({
      title       : {type : String, default : '', trim : true}
    , body        : {type : String, default : '', trim : true}
    , user        : {type : Schema.ObjectId, ref : 'User'}
    , created_at  : {type : Date, default : Date.now}
  })
  
  ArticleSchema.path('title').validate(function (title) {
    return title.length > 0
  }, 'Article title cannot be blank')
  
  ArticleSchema.path('body').validate(function (body) {
    return body.length > 0
  }, 'Article body cannot be blank')
  
  
  mongoose.model('Article', ArticleSchema)
  
subject: add user to articles