Enhancing Event-Based Semantics in the Ontology of Picture Books 2 Karen Ang De La Salle University 2401 Taft Avenue, 1004 Manila, Philippines [email protected]Ethel Ong De La Salle University 2401 Taft Avenue, 1004 Manila, Philippines [email protected]ABSTRACT Picture Books 2 generates fable-like stories for children age 6 to 8 years old based on an input picture comprising of three scenes. Currently the system is able to generate stories that show transitions and movement of characters and objects across the adjacent scenes of the input picture. However some of the stories produced are illogical. This study explores an approach to enhancing the ontology structure and the reasoning engine of the system to produce stories that follow a logical flow. Keywords Picture Books 2, Story Generation, Ontology, Reasoning Engine, World State 1. INTRODUCTION 1.1 Storytelling for Children Many people use storytelling for various reasons, such as sharing their beliefs, culture, and experiences. Also, storytelling has been widely recognized to develop a child’s language and literary skills. It plays a vital role in shaping a child's creativity skills. Children get a chance to practice their imaginations and also relate the stories to their daily lives. During the early years of children, they use drawings to share their stories. Storybooks which contain pictures or picture books are usually the first contact of a child with the world. The combination of art and words is a powerful experience for them. This triggers their imagination and introduces concepts for their cognitive and language development [6]. This idea led to the development of a story generation system, Picture Books [7]. 1.2 Motivation Picture Books 1 [7] takes a single picture as input and generates a story based on the elements (background, characters and objects) in the picture story. However, a single picture may not capture the intended story that has been conceptualized by the child when he/she drew the picture. This motivated the development of Picture Books 2 [1], which takes an input picture containing a sequence of multiple scenes. The system generates fable-like stories that also feature common animals possessing traits as the main characters of the generated story. These character traits comprise the main factor in determining the theme for the story. Furthermore, the system relies on the causal chain of events that may occur in the given scenes to generate a story. The chain of events is defined in the storytelling ontology which was manually populated with activities and concepts that are familiar to the target age group. Validation made by linguists and storytellers on the resulting stories have led to the conclusion that the design of the ontology is insufficient to support the reasoning engine of the story planner. It lacks certain attributes which can contribute to the logical correlation of events to produce a coherent story. Although the ontology design is inadequate, it can still be used to causally connect events. Hence, in this study, the proposed design of the ontology will still utilize the previous structure adapted from ConceptNet [8] while appending other attributes, specifically conditions and parameters needed for an action or event to happen in the story world. 1.3 World State Picture Books 2 reasons through the ontology by retrieving the causal chain of events between the initial state (e.g., the main character arrives at the camp) and the target goal of the story (e.g., the character learns to be brave). Due to solely relying on a causal chain of events, the scoring function used to select an event from a set of candidate events is random. This simplistic approach in story planning combined with a set of binary relations defining events in the ontology did not consistently produce a chain of events that will lead to a coherent story to be generated. Oftentimes, it is necessary to consider the world state to constrain the possible events to be included in the story flow. Tracking the world state as actions and events occur in the story is currently not supported in Picture Books 2. A world state contains knowledge about the state of the different characters and objects in the story and are updated every time a character executes an action that may change not only his/her state, but that of the other characters and objects present in the story world. In [9], this represents the first level of story representation - the semantic networks for story world knowledge. The first level relies on the general ontology of semantic network describing the knowledge about the concepts and possible relations that exist between them. World states or story world description [9] is an instantiation of some concepts in the general ontology which is concerned with the current properties and relationships of a concept in a certain point of time. Although the ontology of Picture Books 2 includes properties and relationships between concepts, no world state has been utilized and updated as the story progresses. Instead it assumed static states, states that do not change over time. Because of this, the scoring function purely relied on a random selection of 81 Proceedings of the 8th National Natural Language Processing Research Symposium, pages 81-84 De La Salle University, Manila, 24-25 November 2011
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Enhancing Event-Based Semantics in the Ontology of Picture ... · Enhancing Event-Based Semantics in the . Ontology of Picture Books 2 . ... which is defined as a chronological sequence
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