Method Schema 
The method schema is a flexible tool for combining various proposal methods (function modules) that make up the prerequisites for generating product proposals. The individual function modules determine products according to a range of criteria and combine these to make product proposals. All types of product proposal are covered: Cross-selling, up-selling, down-selling, top n product lists, accessories, and product proposals with campaign reference.
You can edit the method schema in Customizing for Customer Relationship Management under 
Customer Relationship Management 
Marketing Product Proposals Create Method Schema 
.
Integration
The method schema is the basis for generating product proposals in the Telesales and CRM Web Channel applications.
The accessories integrated into some method schemas originate from the product master data. The accessories for a specific product are maintained in product processing under Relationships.
Features
The following method schemas are delivered as defaults:
Cross-selling
Up-selling
Down-selling
Accessories
Top n list
Cross-selling/Up-selling/Accessories with target group reference
Cross-/Up-/Down-selling/Top n list/Accessories with target group reference
Offers with campaign reference
Cross-/Up-selling/Accessories for global rules as well as rules with target groups or profile reference
Cross-/Up-/Down-selling/Accessories for global rules as well as rules with target groups or profile reference
The customer can also use his or her own function modules and combine these to make individual method schemas. These function modules must have a standardized interface and must be added to the list of permitted function modules. They can then be included in the required method schema.
You can find more information in the IMG documentation under Customer Relationship Management Marketing Product Proposals Create Method Schema .