In relational database model, the schema of a relational database consists of all relation
schemas in database. While in the relational database, a relation schema is a list of the
attributes of a relation, including the domains of the attributes. Before we can store the
geometric data of various house components, we need to define all the relation schemas
for the house database. Since relation schema is used at conceptual level, it is possible
and reasonable to let the representation of relation schemas be independent of specific
data management systems. In this project, we defined a total of 24 relation schemas for
the house database. The data definition language (DDL) is the language used to define the
relation scheme of the database.