1. A method for integrating oilfield data in a plurality of formats, the method comprising: storing the oilfield data associated with a plurality of oilfield entities in a first data repository; obtaining, using a computer, a first target metamodel comprising a first structural description of a first plurality of data entities of the first data repository, wherein the first structural description describes database rows and columns of the first data repository; obtaining, using the computer, a domain metamodel interleaved with a first mapping specification, the domain metamodel comprising a second structural description of a domain model, defining a plurality of domain objects within a hierarchy of an oilfield domain, for representing the plurality of oilfield entities in an application programming interface (API); associating, using the computer, the first plurality of data entities of the first target metamodel with the plurality of domain objects of the domain metamodel using the first mapping specification; forming, using the computer, the API based on the domain metamodel, the first target metamodel, and the first mapping specification; generating a domain model source code based on the domain metamodel, the first target metamodel, and the first mapping specification using an automatic code generator; compiling the domain model source code to implement the API; generating a plurality of domain object instances corresponding to the plurality of oilfield entities, wherein at least one of the plurality of domain object instances is instantiated from a domain object of the plurality of domain objects compiled from the domain model source code; and identifying an association between the plurality of oilfield entities with the first plurality of data entities based on the at least one of the plurality of domain object instances; receiving, by the API, a database operation for the domain metamodel, wherein the database operation comprises a plurality of elements that generate a result using data in the domain metamodel; determining that one element of the plurality of elements in the database operation for the domain metamodel is needed to generate the result in a form required by the database operation; executing the database operation after a status of the one element in the database operation is changed from optional to mandatory, and generating the result in the form required by the database operation.
1. A method for integrating oilfield data in a plurality of formats, the method comprising: storing the oilfield data associated with a plurality of oilfield entities in a first data repository; obtaining, using a computer, a first target metamodel comprising a first structural description of a first plurality of data entities of the first data repository, wherein the first structural description describes database rows and columns of the first data repository; obtaining, using the computer, a domain metamodel interleaved with a first mapping specification, the domain metamodel comprising a second structural description of a domain model, defining a plurality of domain objects within a hierarchy of an oilfield domain, for representing the plurality of oilfield entities in an application programming interface (API); associating, using the computer, the first plurality of data entities of the first target metamodel with the plurality of domain objects of the domain metamodel using the first mapping specification; forming, using the computer, the API based on the domain metamodel, the first target metamodel, and the first mapping specification; generating a domain model source code based on the domain metamodel, the first target metamodel, and the first mapping specification using an automatic code generator; compiling the domain model source code to implement the API; generating a plurality of domain object instances corresponding to the plurality of oilfield entities, wherein at least one of the plurality of domain object instances is instantiated from a domain object of the plurality of domain objects compiled from the domain model source code; and identifying an association between the plurality of oilfield entities with the first plurality of data entities based on the at least one of the plurality of domain object instances; receiving, by the API, a database operation for the domain metamodel, wherein the database operation comprises a plurality of elements that generate a result using data in the domain metamodel; determining that one element of the plurality of elements in the database operation for the domain metamodel is needed to generate the result in a form required by the database operation; executing the database operation after a status of the one element in the database operation is changed from optional to mandatory, and generating the result in the form required by the database operation. 5. The method of claim 1 , further comprising: storing the oilfield data associated with the plurality of oilfield entities in a second data repository; obtaining a second target metamodel comprising a third structural description of a second plurality of data entities of the second data repository; obtaining a second mapping specification associating the second target metamodel with the domain metamodel; and further forming the API based on the second target metamodel and the second mapping specification.