Application-sol interaction: an APL2 approach

ABSTRACT

This paper describes an APL2 application programmer tool which simplifies the development and implementation of APL2 applications which interact with SQL. The described tool consists of a suite of APL2 functions which provide a high level, easy-to-use, application-SQL interface. The interface extends the SQL concepts of tables and operations on tables into the APL2 workspace, providing a simple method of interaction between APL2 applications and SQL. This approach also provides a great deal of isolation between the APL2 code and the SQL code required for manipulating the application's data. Besides simplifying the usage of SQL within APL2 applications, the tool provides a convenient means for “tuning” an application's use of SQL, particularly the SQL SELECT statements used by the application. It also provides a framework for exploring extensions to SQL statements and syntax. While still somewhat experimental, the described tool has been effectively used by inexperienced APL2 programmers with virtually no knowledge of SQL.

REFERENCES

• 1: The programmer tool described here has been under development for several years, evolving with each successive implementation. Initial development efforts were carried out by the author in 1904 while at Decimus Corporation, with programming assistance from Grace LaTorra. This initial version suffered from serious deficiencies in several areas, and did not prove successful in what limited use it received. In the fall of 1985, a complete redesign and implementation was undertaken by the author while at IBM in a consulting capacity; after limited use, it underwent further design modifications to improve the structure of the arguments passed to the table modification functions. Subsequent implementations have concentrated on modeling extensions to SQL and controlling resource consumption resulting from the retrieval of large numbers of table rows. Credit for suggesting that APL2 transaction development could be facilitated by extending the relational database concepts of relations and operations on relations into the active workspace in the manner described here belongs to Gary Beaver.
• 2: SQL/DS (IBM Program Number 5748-XXJ), and DB2 (IBM Program Number 5740-XYR). Although initially developed under a VM environment to interact with SQL/DS, all subsequent work has been carried out using DB2 in an MVS environment.
• 3: Auxiliary Processor 127 is the IBM supplied interface between the APL2 workspace and either SQL/DS (VM environment) or DB2 (MVS environment). For detailed information on AP 127, see "APL2 Programming: Using Structured Query Language (SQL)," (IBM Corporation, IBM Form No. SB20-9217).
• 4: The tool described here is not meant to be a replacement for the functions supplied in the 2 SQL workspace supplied with APL2.
• 5: See "APL2 Programming: Using Structured Query Language (SQL)," Chapter 2, for further details and an additional example.
• 6: 'SQL/Data System Planning and Administration for VM/System Product," (IBM Corporation, IBM Form No. SH24-5043). Chapter 7 discusses logical database design issues for SQL/DS databases.
• 7: "IBM Database 2 Database Planning and Administration Guide," (IBM Corporation, IBM Form No. X26-4077). Chapter 2 discusses logical database design issues for DB2 based databases. It is interesting that both the SQL/DS literature and the DB2 literature recommend that all tables possess a primary key, although neither DBMS requires it.
• 8: C. J. Date, An introduction to database systems: vol. I (4th ed.), Addison-Wesley Longman Publishing Co., Inc., Boston, MA, 1986
• 9: Limited experimentation with permitting updates on APL2-SQL tables based on two underlying SQL tables has been carried out (the key columns from both underlying tables are placed in the APL2-SQL table), but this has not been made available as part of the package. A host of problems arise from this, most involving corruption of the conceptual data model embodied in the SQL tables. It is also not clear that permitting updates on such composite tables is desirable from a programming perspective.
• 10: This approach was chosen since it has a precedent in current SQL, namely, the "SELECT DISTINCT" form of the SELECT statement.
• 11: ORACLE HDMS. For an overview of ORACLE's extensions to SQL, see "ORACLE Overview and Introduction to SQL," (Oracle Corporation, Oracle Part No. 3801).
• 12: Stephen Deerhake, Application screen management: an APL2 approach, ACM SIGAPL APL Quote Quad, v.17 n.4, p.94-102, May 1987

INDEX TERMS

Primary Classification:
  D. Software
  D.3 PROGRAMMING LANGUAGES
      D.3.2 Language Classifications

          Nouns: APL

Additional Classification:
  D. Software
  D.2 SOFTWARE ENGINEERING
      D.2.2 Design Tools and Techniques
          Subjects: Modules and interfaces

  H. Information Systems
  H.2 DATABASE MANAGEMENT
      H.2.3 Languages

          Nouns: SQL

General Terms:
Design, Languages