Hierarchical database conversion with conditional write

In a computer system having a memory and storage device, an improved method for transitioning an input hierarchical database serving as a system input to obtain an output hierarchical database, the method including the steps of

• generating and storing in the memory:
• (i) an input dictionary defining the contents of the input database;
• (ii) an output dictionary defining the contents of the output database, the contents including records composed of segments;
• and (iii) a map table having entries defining the correspondence between the input database contents and selected memory locations,
• identifying, with reference to the input dictionary and the map table, the contents of the input database selected for transitioning, extracting the selected contents from the input database, and storing the extracted contents in the device in hierarchical sequence as identifier-data pairs, and
• sequentially processing the identifier-data pairs with reference to the input dictionary, the output dictionary and the map table, and storing data associated with each identifier as associated data in the memory,
• wherein the improvement to the method comprises the steps of
• before the step of processing, generating and storing derivation table entries in the memory, each of said entries specifying computer instructions to generate the final contents of the output database from the associated data, wherein a first of said instructions unconditionally writes to the device a subgroup of the associated data needed to complete a corresponding subgroup of the output database, and wherein a second of said instructions:
• supplies comparison information expressed in terms of the associated data;
• and conditionally writes to the device a subset of the associated data needed to complete a corresponding subset of the output database, said conditional write executable whenever a comparison between said comparison information and an identifier corresponding to said subset is satisfied, and wherein a third of said instructions executes a data movement from target memory locations to destination memory locations defined by said third instruction, said destination locations storing a part of the output database,
• before the step of processing, generating and storing in the memory a temporary storage dictionary defining the format of data stored in predetermined ones of the selected memory locations,
• before the step of processing, augmenting predetermined map table entries with preselected ones of said derivation table entries callable during the step of processing,
• upon a call to said unconditional write during the step of processing, executing said unconditional write to generate said subgroup of the associated data and then storing said subgroup of the associated data in the device,
• upon a call to said conditional write during the step of processing, performing said comparison and, when satisfied, executing said conditional write to generate said subset of the associated data and then storing said subset of the associated data in the device, and
• upon a call to said data movement during the step of processing, identifying said target memory locations with corresponding ones of said selected memory locations and moving data in said identified target memory locations to corresponding ones of said destination memory locations,
• whereby the improvement effects the transitioning of a large input database by a computer system having insufficient memory to store data for all segments of an output database record until all transitioning operations are completed.