Embedded real-time systems are deployed in a wide range of application domains including transportation systems, automated manufacturing, process control, defense, aerospace, and telecommunications. These systems must satisfy not only logical functional requirements but also para-functional properties such as timeliness, Quality of Service (QoS) and reliability. The cross-cutting behaviors imposed by these para-functional properties and dependencies on operational characteristics (e.g. hardware, OS and middleware platforms used) have traditionally led to hard-to-code, hard-to-understand and hard-to-change software. The net result is that productivity improvements in embedded software development have been miniscule compared to improvements in computing and network technologies. Time Weaver provides a model-based framework that can lead to high degrees of cost-effective reuse of embedded software components. Our framework separates para-functional properties into semantic dimensions (e.g. timing, event flow, concurrency, fault-tolerance, deployment) that can be modified independent of one another. The impact of changes in one dimension on the realization of other dimensions are automatically projected and managed. Platform dependencies are also captured separately, enabling a code-generation subsystem to re-use the same components across a wide range of heterogeneous platforms and applications. System components can be recursively composed or decomposed. An analyzable software structure is enforced such that the end-to-end timing behavior of the resulting system can be verified.