## 2 Food Ontologies
### Food Product Ontology  
The Food Product Ontology [21] describes food products with common representation, vocabulary and language for the food product domain, to help manufacturers, retailers, governments and institutions to publish their data related to this domain in a way that maximizes the reuse of data. The food product ontology allows for better integration, sharing, and collaborative processing of food information among several stakeholders. It extends a widely used standardized ontology for product, price, store and company data, called GoodRelations [28], which is an ontology describing tangible goods and commodity services using structured data in RDF and microformats. The Food Product Ontology was initially built for MneMojno [29], a mobile application that provides users with additional information about a food product that cannot be found on the package, and can assist them in selecting better products.  
The food product ontology can be used to serve various parties as follows: On a retailer Web site, food products have only name, description, image and price. A manufacturer's Web site generally provides more information about their food products such as name, description, images, information about food nutritional value data, contents/ingredients, and other specifications, which are within the domain name space of the respective manufacturer. There may exist actual instances of this food product, or it may inherit its properties from the specifications of food products, which are produced by the same manufacturer. An institution's Web site such as the UK Food Standards Agency [30] publishes a list of approved additives that can be used in food manufacturing. Usually the list has a label and a brief description of the additives. The above three examples (retailer, manufacturer and institution) show possible relationship among these entities. To model this relationship, the Food Product Ontology extended the classes and properties of GoodRelations to include concepts from the food product domain such as Food and Ingredient, and properties such as energy per 100 grams and carbohydrates per 100 grams. GoodRelations has all the representations of a product and its specification, but usually does not provide a relation to a particular domain. The Food Product Ontology is needed to add a food product domain to describe the new classes and properties within that domain. For example, Food is expressed as a subclass of Product or Service class from the GoodRelations that represents any product. The name of a food product can be annotated with gr:name or rdfs:label properties. Ingredient is a subclass of Thing that is the parent class of any class in OWL language. The rdfs:label property is used to describe a label of an ingredient. Food and Ingredient classes are related to each other through the ingredient object property. \"Carbohydrates per 100 g\" is a data property that represents amount of carbohydrates (in grams) per 100 grams a food product has. Properties such as carbohydrates per 100 g, energy per 100 g, proteins per 100 g and fat per 100 g are added to the ontology to simplify a food product representation in RDF. Another addition to the Food Product Ontology is the categories of food products (e.g., eggs and egg products). The food product categories are similar to those defined by the CODEX Alimentarius [31]. The CODEX is an organization established by the World Health Organization and FAO. The category system consists of 16 top categories and more than 300 subcategories, with maximum depth equal to 4. An example of the Food Ontology Classes is shown in Figure 3.  
It is worth noting that [PERSON], one of the developers of the Food Product Ontology, is also working with others on a related FOODpedia, a DBpedia of Food Products [32, 33].