XML is a true double-edged sword in the data analytics world, with both advantages and disadvantages not unlike relational databases or NoSQL. The global advantages and disadvantages inherent in XML are just as applicable in the healthcare field. For example, consider the flexibility of user-created tags on the fly—something that is both an advantage (for ease of use, compatibility, expandability, et cetera) and disadvantage (lack of standardization, potential incompatibility with user interfaces, et cetera) in the global sphere. These are equally applicable in healthcare settings. Considering an electronic health record (EHR), different providers and points of care may add to the EHR without having to conform to the standards of other providers; that is, data from a rheumatologist may be added to the patient record in with the same ease as a general practitioner or psychologist. The portability of the XML format means that the record can be exchanged amongst providers or networks as long as the recipient can read XML. However, this versatility comes at a price, as the lack of standardization means that all tags and fields in any given record must be known prior to query and can be quite a time-consuming process.
Considering an analogy to a different industry, think of a consumer packaged goods (CPG) manufacturer. The CPG has its own internal master data schemas in relational databases and reserves XML for its reseller data interface, so that the different wholesalers and retail network can share sales data back to the CPG in a common format. While all participants use a handful of core attributes (e.g., manufacturer SKU and long description), each wholesaler and retailer has its own set of attributes that are proprietary. XML allows the different participants to feed data back to the CPG without conforming to a schema imposed across the entire retail network and allows the CPG to glean the requisite data shared amongst all participants. However, the process requires setting up the known tags for each new participant so that the CPG knows ahead of time what specific tags are relevant to each participant.
Brewton, J., Yuan, X., & Akowuah, F. (2012). XML in health information systems. Paper presented at the World Congress in Computer Science, Computer Engineering, and Applied Computing, Las Vegas, NV.
Jumaa, H., Rubel, P., & Fayn, J. (2010, 1-3 July 2010). An XML-based framework for automating data exchange in healthcare. Paper presented at the The 12th IEEE International Conference on e-Health Networking, Applications and Services.
Stockemer, M. (2007). How Do HL7 and XML Co-Exist in Clinical Interfacing? Retrieved from https://healthstandards.com/blog/2007/08/10/how-do-hl7-and-xml-coexist-in-clinical-Most content also appears on my LinkedIn page.