1. A system, comprising: one or more computing devices configured to implement a plurality of computing resources, wherein the plurality of computing resources comprise a data source; and one or more computing devices comprising at least one processor and at least one memory, wherein the at least one memory stores program instructions executable by the at least one processor to implement a query service, wherein the program instructions are executable by the at least one processor to: receive a description of the data source; generate a table definition for the data source based on the description of the data source, wherein the table definition maps the data source to one or more columns of an output table; select a parser for the data source, wherein the parser is selected from a set of predefined parsers based on the description of the data source, and wherein the parser comprises a serializer and a deserializer for the data source; receive, from a client, a query against the data source, wherein the query is expressed in a query language and describes one or more attributes of data to be obtained from the data source; retrieve, from the data source, one or more elements of data responsive to the query using the selected parser, wherein the one or more elements of data are selected from the data source based at least in part on the one or more attributes of data in the query; and transform the retrieved one or more elements into the output table based on the table definition.