### THL Persistency Layer

#### Easily integrate relational data with your VisualAge for Smalltalk applications

THL Persistency Layer is a framework for mapping an object model to relational databases. As a layer between the VisualAge Database Parts and your object model it shields the developer from the api-level of accessing a database.

#### Features

- Visual editor for mapping classes to tables You use an editor similar to VA's public interface editor to define the mapping of attributes to columns and/or referenced classes
- Support for 1:1 and 1:n relationships and inheritence Don't care about foreign keys and this stuff. Simply define the mapping once and forget about relational restrictions. THL Persistency Layer keeps track of all these things.A referenced table/class is simply an attribute in your object model, inheritence is fully transparent.
- Consinstency checking THL Persistency Layer can check the consistency of relational data in the object model. You can define attributes as primary key or simple NOT NULL columns. THL Persistency Layer checks these conditions before everey write-access to the DB.
- Object Identity and Caching THL Persistency Layer keeps track of all loaded objects in your image. There will not be a copy of an object in the same image.
- Type transformation allows you to store an attribute's value in any form you want. You might, for example, want to store a Boolean as a VARCHAR value ("true","false") or as a SMALLINT (0 , 1). Just define a piece of Smalltalk code to manage the conversions at read/write time.

#### Benefits

- Protection of your investments THL Persistency Layer allows you to use legacy data in up-to-date, object oriented applications
- Improved productivity Don't invent the wheel every time you need a Database, but reuse the strengths of a reliable framework.

#### Requirements

THL Persistency Layer was written for VisualAge for Smalltalk 4.0. Earlier Versions are supported on request. Using only the database parts of VisualAge for Smalltalk, it is operating system-independent and supports all relational databases supported by VisualAge for Smalltalk.

#### Availability and Pricing

A framework is something alive. It grows with every project. So it is never really finished. The current Version 1.1 of THL Persistency Layer is shipped with complete documentation in HTML. The price is DEM 500,- plus VAT and pp (approx. US $280) per developer seat. Please ask for volume discounts and services.

#### The company

Founded 1995 in southern Germany, THL EDV-Systeme has specialized on object-oriented application development and component technology. In various customer projects we implemented controlling and project management solutions for the software/consulting, trade and finance industry.

| THL EDV-Systeme Joachim Tuchel, Thomas Harich, Nenad Latinovic GbR Haeslenweg 28 D-71642 Ludwigsburg phone: +49 7141 25 75 80
fax: +49 7141 92 19 30
email: jtuchel@t-online.de
Web: http://www.thl-edv.com (under construction)

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