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17.2.9 CASE Tools

MOVIE Server is a large C program and it requires appropriate software engineering tools for its development.

Commercial software systems are usually developed in terms of sophisticated commercial CASE tools. In the academic environment, one rarely builds large production systems and one usually uses simpler, lower level tools based on dialects of the UNIX shell, most typically the C shell which forms now the standard text-mode UNIX interface on most workstations. The C-shell-based environment is most natural in the research working mode where the code is usually of small or moderate size, its typical lifetime is short, and it undergoes a series of major changes during the development cycle. These changes are often of unpredictable character and hence difficult to parametrize a priori in the form of some high-level CASE tools.

MOVIE project aims at the large, commercial quality production system, and yet it is created in the academic environment and contains substantial research components in the domain of HPDC. We therefore decided to select a compromise strategy and to start the MOVIE Server development process in terms of simple, custom-made, C-shell-based CASE tools. More explicitly, the current generation of CASE tools for MOVIE is structured as the interpreter of a very simple high level object-oriented language called MetaShell, designed as a superset of the C-shell. In this way, we assure the compatibility with the standard academic environment and, at the same time, we provide somewhat more powerful software development tools than those offered by the plain text-mode UNIX environment.

A more functional language model for the CASE tools in MOVIE would be provided by the MovieScript itself due to its high-level features and the built-in GUI support but we need a consistent bootstrap scheme in such a process. A natural approach is to use C shell to build MOVIE 1.0, then use its MovieScript to build MOVIE 2.0, and so on. Alternatively, we can consider the task of building high-quality visual ``intelligent'' CASE tools as one of the MOVIE 1.0-based application projects. We discuss these future plans is Section 17.2.10 and here we present the current MetaShell model from the MOVIE developer's point of view. The detailed technical documentation of the MetaShell tools can be found in [Furmanski:92c].

Figure: Sample Elements of the $MOVIEHOME Directory Tree. Dark blobs represent system nodes/names, shaded blobs represent user-provided nodes/names within the M-tree model. For example, each new type, such as Dict, automatically generates its subtree containing the following directories: Fcn (low-level object functions, used for implementing other object components), Act (object-dependent methods for polymorphic operators), Msg (methods implementing object messages), Const (predefined default instances of a given type), Lib, and (C libraries of object functions).

The entire code volume associated with MOVIE is stored in the directory $MOVIEHOME, shown in Figure 17.8 installed as the UNIX environment variable and used as the base pathname for the MetaShell addressing modes. The most relevant nodes in this directory are: bin, sys, and M. The bin directory, to be included in the developer's path, contains the external binaries such as the main MetaShell script and the MOVIE Server binary. The sys directory contains diverse system-level support tools-for example, the C and C-shell code implementing the MetaShell model. The server code starts in the subdirectory M and we will refer to the associated directory tree, starting at M, as the M-tree.

M branches into a set of base software categories such as, for example: Op (C or MovieScript source files implementing methods for the MovieScript operators), Lib (C language libraries), Err (MovieScript error operators), Key (system name objects), Type ( MovieScript types), Shell (MovieScript shell objects) and so on.

Some of these nodes are simple, that is, they contain only a set of regular files (e.g., M/Op); some are composite, that is, they branch further into subdirectories (e.g., M/Lib which branches into system libraries). In the current implementation, the maximal branching level is five (e.g., directory M/Type/String/Lib/regex, which contains the string type library functions for handling regular expressions). Many structural aspects of the system can be presented in the form of some suitable M-tree mappings, listed below:

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Next: MetaDictionary Up: 17.2 System Overview Previous: 17.2.8 ``In Large'' Extensibility

Guy Robinson
Wed Mar 1 10:19:35 EST 1995