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DeepWeaver-1 is a tool supporting cross-cutting program analysis and transformation components, called "weaves". Like an aspect, a DeepWeaver weave consists of a query part, and a part which may modify code. DeepWeaver's query language is based on Prolog, and provides access to data-flow and control-flow reachability analyses. DeepWeaver provides a declarative way to access the internal structure of methods, and supports cross-cutting weaves which operate on code blocks from different parts of the codebase simultaneously. Deep-Weaver operates at the level of bytecode, but offers predicates to extract structured control flow constructs. This paper motivates the design, and demonstrates some of its power, using a sequence of examples including performance profiling and domain-specific performance optimisations for database access and remote method invocation. Introduction. Aspect-oriented programming tools, such as AspectJ [12], can be used to implement performance optimizations. However, tools like AspectJ are too weak, both to perform interesting optimizing transformations, and to capture the conditions for their validity. Similar problems arise when using AspectJ for static program analysis, e.g. to check usage rules for library code, or to detect software defects. For many, this is a consequence of deliberate simplicity in the aspect language design. This paper presents a prototype system which is powerful enough to express complex analyses (and transformations)-yet, like an aspect weaver, retains a declarative style by which some simplicity can be retained. The tool is motivated and illustrated using a series of examples, including intramethod performance profiling, and domain-specific optimizations for database access and remote method invocation. Example. We begin with a very simple motivating example, a domain-specific performance optimisation for Java code that uses the JDBC (Java Database Connectivity) library. Consider this Java fragment: ResultSet staff = statement.executeQuery("SELECT * FROM employees"); ResultSet clients = statement.executeQuery("SELECT * FROM customers"); ... complex and messy code that uses clients but not staff ...

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