A computer-implemented method for implementing a defaulting framework for definition, selection and rendering of an image of a customized product, comprising the steps of: forming key-value expressions using attributes and attribute values associated with the attributes that define a custom product; wherein the attributes comprise a first attribute and a second attribute; matching the key-value expressions against default filters to identify a default filter; based on the default filter, selecting a first default value for the first attribute of the custom product; applying the first default value to the first attribute to define the custom product; rendering a first image of the custom product having at least the first attribute; further comprising receiving an updated first attribute value defining an attribute of the custom product; in response to receiving the first updated attribute value, determining a legal set of updated attribute values for the second attribute, wherein the legal set of updated attribute values identifies one or more attribute values of the second attribute of the custom product or an accessory product that are compatible with the updated first attribute value; forming an updated key-value expression using the updated first attribute value associated with the attributes that define a custom product; matching the updated key-value expression against default filters to identify an updated default filter; based on the updated default filter, selecting an updated first default value for the first attribute of the custom product; applying the updated first default value to the first attribute to define the custom product; selecting an updated second default attribute value of the updated second attribute of the custom product, wherein the selection is limited to selecting a second attribute value within the legal set of updated attribute values for the second attribute; at the time that a user is designing the customized product, querying a database of products or other information modeling element about what attributes and related products or accessories are valid or otherwise allowed; and rendering an updated image representative of the custom product having the updated first attribute value for the first attribute. forming key-value expressions using attributes and attribute values associated with the attributes that define a custom product; wherein the attributes comprise a first attribute and a second attribute; matching the key-value expressions against default filters to identify a default filter; based on the default filter, selecting a first default value for the first attribute of the custom product; applying the first default value to the first attribute to define the custom product; rendering a first image of the custom product having at least the first attribute; further comprising receiving an updated first attribute value defining an attribute of the custom product; in response to receiving the first updated attribute value, determining a legal set of updated attribute values for the second attribute, wherein the legal set of updated attribute values identifies one or more attribute values of the second attribute of the custom product or an accessory product that are compatible with the updated first attribute value; forming an updated key-value expression using the updated first attribute value associated with the attributes that define a custom product; matching the updated key-value expression against default filters to identify an updated default filter; based on the updated default filter, selecting an updated first default value for the first attribute of the custom product; applying the updated first default value to the first attribute to define the custom product; selecting an updated second default attribute value of the updated second attribute of the custom product, wherein the selection is limited to selecting a second attribute value within the legal set of updated attribute values for the second attribute; at the time that a user is designing the customized product, querying a database of products or other information modeling element about what attributes and related products or accessories are valid or otherwise allowed; and rendering an updated image representative of the custom product having the updated first attribute value for the first attribute.