Data Management & PDM: Comparing CAD Files and Databases

Managing files in folders on a desktop is fine for family photos and videos, but for valuable intellectual property such as CAD files, you’ll need a safer and more robust data management strategy.

Files are easily lost, corrupted, and overwritten. Adding a Product Data Management (PDM) system on top adds a thin layer of security to file-based data storage, along with easier access from a central company server.

However, PDM systems eliminate efficient CAD collaboration. With a library-card-like procedure, only one engineer at a time can check a file in and out of the “digital lockbox.”

“Fileless” data management systems simply improve the interface of the PDM system without any real benefits to the designer.

Onshape’s cloud-native database is the only CAD data management architecture that can simultaneously deliver data security, real-time team collaboration, and seamless workflows – because it doesn’t hide files; it eliminates them entirely.

Why Engineers Shouldn’t Have to Think About Data Management

Even among very tech-savvy engineers, there is still a lot of confusion about what it means to store design information in a file versus a database.

In a LinkedIn discussion, the following question came up:

A better first question: Why should engineers need to know the intricate details of how their data is stored at all?

What engineers actually need to know is what they can and can’t do with their data, and what overhead the system creates for them every day. The more an engineer has to think about data management – saving, checking in, resolving conflicts, finding the right version – the more it negatively impacts their design processes, their deadlines, and their budgets.

Making a clear distinction between files and different types of database storage is indeed a complex issue. Some may dismiss this as semantics, but there are clear advantages to one particular method of data storage.

So let’s review the different ways that CAD data can be stored and how they impact your business.

The Four Ways CAD Data Can Be Stored

1. Data Storage in a File

This is the easiest one to explain. Anybody who has ever used a computer to create something – an image, a spreadsheet, or a CAD design – has saved their data into a discrete file on their local hard drive.

Each file type has its own unique data structure that records all the information in a format only the software that created it can understand. Therefore, anybody with the same version of the same software as you can open and edit your file. Proprietary file structures can also be easily reverse-engineered to extract the necessary information (the DWG file format being the prime example).

Most experts would agree that computer files are an extremely insecure method of storing data. Files are easily mislaid, corrupted, or overwritten. Files get copied and emailed everywhere, and nobody knows who has what or which copy is the latest version.

That’s why every CAD vendor has its own bolt-on PDM software that they can charge extra for.

2. Data Storage in a PDM Database

This statement is misleading. Your data is not stored in a PDM database, but is still stored in files on a file server with all the inherent issues mentioned above.

What is stored in the PDM database is data about your data, otherwise known as “metadata.” It’s like keeping a Rolodex or library card system to keep track of where files are kept and a brief summary of what each file contains. To find a file, you consult your index card to find where the file is stored and then copy it to your local hard drive, known as “checking out” the file (just like a library book).

All PDM databases use what is called a relational database. These databases store metadata in fixed tables with rigid schemas and pointers linking multiple tables together. This enables data to be structured and categorized so that it can be indexed, searched, and easily manipulated using Structured Query Language (SQL) transactions.

For a CAD file, a table may state what type of file it is, where it is stored, list all of its custom properties, and have links to the assembly or project that it belongs to. A simple SQL query is able to extract all the information about a file and its relational hierarchy to all the other files in your database.

This means that finding files is fast, but in order to work on them, you must check them out and have them copied locally to your hard drive. Keeping with the library book analogy, once a copy of the file is checked out, it is no longer available to others who wish to access it. You can still see the library card data and a view-only representation of the file, but the file itself can’t be copied or edited.

In practice, this system of checking CAD files in and out of a digital lockbox further exacerbates PDM system issues, interferes with workflow, and reduces product-to-market speed. The bigger the team and the more agile the design process, the bigger this problem becomes.

Once CAD files are checked out of a PDM system, they are uncontrolled. They can be copied and emailed at will, posing another huge security threat and the possibility of a supplier manufacturing the wrong version of a part.

3. Data Storage in a “Fileless” CAD Database

This statement is also misleading. Some CAD systems have introduced a “new” type of file storage system – the so-called “fileless,” “no file” or “zero file” database. The end user only ever interacts with the PDM interface and never sees the actual CAD files.

However, the files are downloaded in the background when a user wishes to work on them. If you know where to look, you’ll find them hidden in an obscure area of your hard drive. While these files can be technically referred to as a cache, they still contain the editable CAD data and each file must first be downloaded before the CAD system can open it.

There are advantages to fileless CAD data storage. First, there is a central file store so that anybody can get the data they need without having to worry about where any of the files are located (the same as regular PDM, really). Second, the cached files are sufficiently hidden and obfuscated so that they can only be opened by the installed CAD system and therefore can’t be emailed.

The downside to this method is that it doesn’t really offer any real benefits in comparison to a traditional PDM system. When a part needs to be edited, it is downloaded locally on the user’s hard drive and locked so that nobody else can edit it.

Sound familiar? This is akin to checking out the data from a file-based PDM system. Once an edit is complete, the part file is committed back to the database (a.k.a., save, upload, and check-in), which, for a large file, can take some time while the file is copied back to the server over the network or the internet.

I can see why people are confused and struggle to understand the differences.

Since this type of database is based on SQL with rigid schemas that can’t be easily changed, just like regular PDM, this type of system requires periodic maintenance downtime to install service packs and upgrades.

These are old technologies with a new lick of paint.

4. Data Management in Onshape’s Database

The final type of database structure is the one that, in CAD terms, is unique to Onshape.

Onshape uses a document-oriented database model that supports various forms of data and completely flexible schemas. It is a highly performant and distributed non-relational database that is used in big data applications and other processing jobs involving data that doesn't fit well in a rigid relational model. Instead of using tables and rows like relational databases, a non-relational database architecture is made up of collections and documents.

“So what?” I hear you say.

This fundamental difference is what enables real-time CAD collaboration, simultaneous editing, instant and secure sharing, version control, and release management. No other product development platform comes close. There are definitely NO files here.

What Database Architecture Makes Possible

Onshape’s Data Management Advantage

In plain terms, CAD collaboration in Onshape allows entire design teams to work on the same project, same assembly, same part, and even the same sketch if need be, at the same time.

Nothing is locked. All design activities are carried out in parallel. As changes are made, every action is recorded in the database and instantly updated wherever it’s used. There is no save button, no check-in / check-out, no accidental overwrites, and no waiting around for someone else to finish their work before you can start yours.

This enables teams to co-design complex parts and assemblies without having to be physically in the same location. Since every design change is recorded, conflicts are easily resolved. Your team can experiment as much as they like, either in the same workspace or in their own branch, confident in the fact that any errors or bad decisions can always be undone. In short, Onshape gives you unlimited undo/redo.

With dedicated servers, data encryption, and third-party security testing, Onshape protects your CAD data when sharing with colleagues, suppliers, or customers. Just like Google Docs, all you need to do is enter a person’s email address, set view or edit permissions, and press “Share.”

Clicking on the email link will open your design in a web browser or a mobile device. No software or downloads are required. This enables design teams to work together from anywhere and to carry out design reviews in real time on any device. Everybody works on the exact same document, not different copies of the data. Access is just as easily revoked.

These are just some of the powerful, time-saving benefits that Onshape’s unique CAD database architecture delivers. And I haven’t even mentioned Onshape’s CAD features.

Are You Storing CAD Data in Files or a Database?

To revisit the LinkedIn question: The confusion is understandable, because most CAD vendors use the word “database” to describe systems that are, at their core, still file-based. The honest answer is:

The more an engineer has to think about CAD file management, the more time they’re spending on infrastructure instead of design. The goal of any good CAD data management system should be to make itself invisible.

(This blog was originally published March 24, 2019.)