Managing sets of entities

Abstract

Methods and apparatus, including computer systems and program products, that implement a description language and a parser for a description language. A method includes receiving input including a specification of base items, a specification of contexts, and a specification of a selected context from the contexts. The method further includes generating an output set of items by evaluating the selected context. In that method, each item in the output set of items includes core attributes of a corresponding base item and can include attributes from a context. Generating an output set of items can include generating a specific bill of materials.

1 . A machine implemented method of generating enriched sets of items, the method comprising: 
 receiving input comprising: 
 a specification of base items, each of the base items comprising one or more core attributes and a value assigned to each core attribute;  
 a specification of a plurality of contexts, one or more of the contexts comprising: 
 a definition selecting a set of items from the base items, one or more contexts, or both; and  
 a definition selecting one or more additional attributes for one or more of the items in the set of items, and a value assigned to each additional attribute; and  
 
 a specification of a selected context from the contexts; and  
   generating an output set of items by evaluating the selected context, wherein evaluating the selected context comprises: 
 evaluating a definition selecting a set of items for the selected context in order to generate the output set of items, and  
 evaluating a definition selecting additional attributes for the selected context in order to determine which additional attributes and values of additional attributes are to be included in each item in the output set of items.  
   
   
   
       2 . The method of  claim 1 , wherein at least one of the contexts in the plurality of contexts comprises a definition of a specific bill of materials for a product and the selected context comprises the definition of a specific bill of materials, wherein generating an output set of items comprises generating a specific bill of materials from the definition of a specific bill of materials.  
   
   
       3 . The method of  claim 2  further comprising: 
 generating the product comprising materials matching the output set of items according to attributes of the output set of items.    
   
   
       4 . The method of  claim 4 , wherein the definition selecting a set of items from the base items, one or more contexts, or both comprises selection criteria that further defines the set of items to include or exclude one or more items from the base items, one or more contexts, or both.  
   
   
       5 . The method of  claim 1 , wherein the definition selecting a set of items from the base items, one or more contexts, or both comprises set operations to be used in combining sets of items from two or more contexts from the plurality of contexts.  
   
   
       6 . The method of  claim 1 , wherein the definition selecting a set of items from the base items, one or more contexts, or both comprises selection operations to be used in selecting items from the plurality of contexts.  
   
   
       7 . The method of  claim 1 , wherein the definition selecting one or more additional attributes defines a type of each of the additional attributes.  
   
   
       8 . The method of  claim 7 , wherein the type of each of the additional attributes is either a default type or an override type, wherein a default type additional attribute is overridden by a core attribute having a matching name, and an override type additional attribute overrides a core attribute having a matching name.  
   
   
       9 . The method of  claim 1 , wherein one of the plurality of contexts essentially consists of a first definition selecting a set of items from the base items, one or more contexts, or both.  
   
   
       10 . The method of  claim 1 , wherein at least one of the base items comprises one of a strong core attribute, one of a weak core attribute, or both; strong core attributes maintaining their assigned value regardless of a context in which a base item resides and weak core attributes being overridden by other attributes having a matching name and being inherited from a context.  
   
   
       11 . A computer program product, stored on a machine-readable medium, the computer program product comprising instructions operable to cause data processing apparatus to: 
 receive input comprising: 
 a specification of base items, each of the base items comprising one or more core attributes and a value assigned to each core attribute;  
 a specification of a plurality of contexts, one or more of the contexts comprising: 
 a definition selecting a set of items from the base items, one or more contexts, or both; and  
 a definition selecting one or more additional attributes for one or more of the items in the set of items, and a value assigned to each additional attribute; and  
 
 a specification of a selected context from the contexts; and  
   generate an output set of items by evaluating the selected context, wherein evaluating the selected context comprises: 
 evaluating a definition selecting a set of items for the selected context in order to generate the output set of items, and  
 evaluating a definition selecting additional attributes for the selected context in order to determine which additional attributes and values of additional attributes are to be included in each item in the output set of items.  
   
   
   
       12 . The computer program product of  claim 11 , wherein at least one context of the plurality of contexts comprises a definition of a specific bill of materials for a software product and the selected context comprises the definition of a specific bill of materials, wherein the instructions operable to generate an output set of items comprises instructions operable to generate a specific bill of materials from the definition of a specific bill of materials.  
   
   
       13 . The computer program product of  claim 12  further comprising instructions operable to: 
 generate the software product including the materials listed in the specific bill of materials.    
   
   
       14 . The computer program product of  claim 11 , wherein the definition selecting one or more additional attributes defines a type of each of the additional attributes.  
   
   
       15 . The computer program product of  claim 14 , wherein the type for each of the additional attributes is either a default type or an override type, wherein a default type additional attribute is overridden by a core attribute having a matching name, and an override type additional attribute overrides a core attribute having a matching name.  
   
   
       16 . A parser to perform tasks comprising: 
 receiving input comprising 
 a specification of base items comprising core attributes and values assigned to the core attributes;  
 a specification of multiple contexts, at least one of the contexts comprising a definition selecting a set of items from the base items, one or more contexts, or both; and a definition selecting additional attributes for one or more of the items in the set of items; and  
 a specification of a selected context to evaluate; and  
   generating a list of enriched items by evaluating the selected context, wherein generating the list of enriched items comprises: 
 for the selected context, evaluating a definition of a set of items in order to generate the list of enriched items, and  
 evaluating a definition of additional attributes of the selected context in order to determine which additional attributes and values of additional attributes are to be included in each of the enriched items, wherein core attributes of an item are included in a corresponding enriched item, and some of the core attributes of an enriched item are assigned values from the additional attributes of the selected context.  
   
   
   
       17 . The parser of  claim 16 , wherein the selected context references one or more additional contexts and generating a list of enriched items comprises evaluating the additional contexts referenced in the selected context.  
   
   
       18 . The parser of  claim 16 , wherein additional attributes are either of a type default or of a type override.  
   
   
       19 . The parser of  claim 17 , wherein a value of an additional attribute defined for the selected set of items is not included in the context if there is a core attribute that has a matching name and the attribute of the context is a default type attribute.  
   
   
       20 . The parser of  claim 17 , wherein a value of an additional attribute defined for the selected set of items is included in the context if there is a core attribute that has a matching name and the attribute of the context is an override type attribute.