Because the construction of the DAS and DDS objects requires that an entire data set be scanned, it can become very inefficient to continually rebuild these objects. Because the DAS and DDS server programs use a text representation for transmission of this object from the server to the client, and because text is easily stored by computer systems, it is possible to store both the DAS and DDS objects once they have been created. Subsequent accesses to these objects can be accomplished by reading and transmitting the textual representation without, in the case of these two programs, actually building the binary data object.
When taking advantage of this optimization, it is important that the server check the date stamp of the DAS/DDS text objects and compare it to the latest modification date of the data set. For any data set to which new data is periodically added, the DAS/DDS text object must clearly be updated so that the cached text object matches exactly the object that would be created if the object were built by querying the data set.
The update of the DAS/DDS text object can itself be optimized significantly. It is not actually necessary to completely re-read the entire data set. Because the software used to build both the DAS and the DDS binary objects work incrementally, it is possible to read the DAS/DDS text object into memory (i.e., build the binary object from its text representation) and then read only the new parts of the data set. The binary object will be added to as needed. NB: The DAS/DDS software may not properly update changed data (data that was present in the previous incarnation of the data set, but is now different in the current version) nor is it straightforward to remove data which is no longer present in the data set.