4 Mar 1998

by Duncan Dwelle

Skip to the Bottom Line

ERwin 3.0, with modest remodeling and several new features, still calls to mind the familiar brown UPS truck - it turns no heads by sleekness but shows up every day in almost every business. Perhaps the next version of ERwin, due shortly, will remind us more of FedEx.

Scope

Although the details of these additional products are outside the scope of this review, it is important for you to know that ERwin exists within a larger framework of integrated and related products.

What's New

Separation of logical and physical models is fundamental in ERwin 3.0. But the actual benefits are limited so far.

While there is still no way to perform selective denormalization, the new "logical only" property on entities, attributes, and relationships allows substantial differentiation of logical and physical models.

Views are provided, albeit incompletely, in an attractive and simple approach.

The primary editor interfaces have been refreshed and simplified.

We'll expand on these issues and others below.

Logical vs. Physical Models

For example, many-to-many relationships now appear immediately in the physical model as associative tables when you select Physical Model from the menu drop-down list.

An associative table can have columns added which will not be represented in the logical many-to-many relationship (a very questionable practice in our opinion).

You can also choose in the logical model to permanently convert the relationship into an associative entity, which is the path we strongly recommend.

The biggest benefit of the separation of logical and physical diagrams is probably how the various editors are simplified. Since there are fewer properties to be shown (i.e., either logical or physical, but not both), the new editor formats are less cluttered.

However, this separation makes no provision for meaningful denormalization, which is the only real reason for having separate diagram forms. Columns cannot be moved or replicated in the physical with any link to their source attributes in the logical model. Furthermore, since both logical and physical models work from the same underlying metadata, you cannot propagate one logical into multiple physical models (for different database products, configurations, or trial versions) without a crude "save as" or copy. Either of those, of course, will break the links of the new model from its origin.

In the foreseeable future this architecture may lead to more useful capabilities if Logic Works can add specific denormalization transformations. Meanwhile, with these limitations we find ERwin's separation of logical and physical models to be more a workaround for poor interface design than a real modeling benefit.

Logical Only / Physical Only Properties

These setting options may seem trivial but they provide several valuable capabilities. One can mark objects as Logical Only if they are in process and not yet ready for exposure to the real world. On the physical side, Physical Only provides a poor man's denormalization if you want to manually represent column moves and replications without forcing the same form in the logical model. This is also useful to model technical columns and tables from the physical side without cluttering up the logical (although we would pursue other means).

While we'd like to see true normalization controls in the tool, this classification ability is very useful in its own right and is a fine addition to ERwin.

Views

Unfortunately, several of the most important elements in a view are not provided. The where clause is left to the user to code. There is no provision for group by, having, or order by, all of which are fundamental to any SQL query. PowerDesigner 6.0 does a much better job here, filling in the join portion of the where clause automatically and offering tabs for the other definition components.

Usability

Nonetheless, we think that ERwin is still neither pretty nor friendly once you dive into the dreaded editors. You can navigate from the attributes of an entity to the descriptive properties of that entity but not the other way around. Adding an attribute in the editor imposes another dialog box on top of the one you're in, rather than accepting entry into a grid or list. The multiple Display levels and Editor styles remain ERwin's most confusing aspects.

As noted in our last review, every window is organized differently. Many options, even important concepts, only appear as obscure buttons nested several windows deep. Some are now only available from the right mouse menu. There is no apparent design pattern or template from which new features are added or old ones enhanced.

We find it inappropriate that the tool which claims to be the leader in database design cannot do a better of interface design. As we said before, if you want to learn ERwin, you're going to do it the hard way - by banging your fingers on keys and your head against the wall

On the other hand, ERwin's manuals and help are generally excellent - well organized, well written, and providing extensive discussions of concepts with examples. Feature creep has gotten ahead of the indexing (both printed and on-line) so it is often a goose chase to look up a specific feature. But when you find it, the explanation will probably be clear and complete.

On balance, we continue to rate ERwin as clumsy and ugly but entirely usable.

The Bottom Line

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Contact

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