Hierarchical modularity

Abstract

To cope with the complexity of very large systems, it is not sufficient to divide them into simple pieces because the pieces themselves will either be too numerous or too large. A hierarchical modular structure is the natural solution. In this article we explain how that approach can be applied to software. Our compilation manager provides a language for specifying where individual modules fit into a hierarchy and how they are related semantically. We pay particular attention to the structure of the global name space of program identifiers that are used for module linkage because any potential for name clashes between otherwise unrelated parts of a program can negatively affect modularity. We discuss the theoretical issues in building software hierarchically, and we describe our implementation of CM, the compilation manager for Standard ML of New Jersey.

A variability-aware module system

“…Our module system offers a clean solution to decompose a product line into smaller subproduct lines, including a suitable decomposition of the variability model, enforcing information hiding with variable interfaces. In this context, it is useful to adopt the notion of hierarchical modularity [11] and provide a richer composition language as outlined in Section 3.4. Supporting composition in hierarchical form allows resolving possible composition conflicts locally, at lower levels of the hierarchy.…”

A Separate Compilation Extension to Standard ML (Revised and Expanded)

“…Formally, the rules satisfy the following property. 4 If L 1 = sdecs 1 → sbnds : sdecs and decs L 1 ok and decs, sdecs 1 , sdecs L 2 ok, and…”

Lightweight prevention of architectural erosion

“…To be achieved, the implementation language must support both the hierarchical structuring of the components and the definition of inter-component relationships. Unfortunately, most modern languages don't have such facilities [2]. What can be relied on, however, is the availability of a hierarchical (tree-oriented) file store.…”

“…In this example, AnApplication has a public method 'getDA()' that returns a ADataAccess class. This is then added to the list of dependencies (2). It is then determined whether or not there are any publicly accessible methods or attributes on the ADataAccess class, which in this case there are not, as ADataAccess's dependencies on ADataStore are not exposed outside the implementation of this class.…”

“…Many of the features and benefits of MILs have been incorporated into modern programming languages. However, not all of these features were carried over [2], and it is the deficiencies that the ArchAngel system addresses. Essentially, ArchAngel takes the syntactic and semantic knowledge in an implementation language's static structure and adds rules to this base that are to be checked.…”