19. A computing system comprising: a data storage medium; and a data storage system to manage storage and access of data in the data storage medium, wherein data is stored as instances of data item types for specific types of data, which are defined in type schemas, and wherein the data storage system provides programmatic access to a system service to generate content index information for data items by (i) generating a schema file that includes a data item type definition for a data item type and content index definitions for the data item type defined in said schema file, wherein the content index definitions are defined using a type-definition language to declare a content index on properties of the data item type defined in said schema file, and (ii) installing the schema file to generate content index information for the data item.
19. A computing system comprising: a data storage medium; and a data storage system to manage storage and access of data in the data storage medium, wherein data is stored as instances of data item types for specific types of data, which are defined in type schemas, and wherein the data storage system provides programmatic access to a system service to generate content index information for data items by (i) generating a schema file that includes a data item type definition for a data item type and content index definitions for the data item type defined in said schema file, wherein the content index definitions are defined using a type-definition language to declare a content index on properties of the data item type defined in said schema file, and (ii) installing the schema file to generate content index information for the data item. 20. The system of claim 19 , wherein the data storage system provides programmatic access to the system service to generate content index information for data items by annotating type-properties declared in the schema file by marking said type-properties for content indexing using the type-definition language.