Let us suppose, for the heck of it, that at one time or another you went for the purchase or were delegated with the responsibility to make a purchase of a dress or shirt for a loved one; you would also love to see this relative in a smashingly hot dress.

There is all kinds of us: the massif, skinny and others still wearing a size somewhere within the upper and lower bounds of the size spread. You also happen to know your loved one's taste.

You go to a sophisticated store to execute this purchase. By sophisticated, I mean one with a large selection of similar items of different sizes, design and color.

So now you've found the spot where what you are looking for is likely be. Eventually, you find just what you want; one that will be precisely your loved one's fitting.

You are an engineer. 1st you conceive a beautiful thought - buying or being delegated with the responsibility to buy a nice dress for a loved one; but until you see a great selection of the item, you cannot narrow your choice to the precise fitting of your loved one. As the selection is made, it is fine tuned to meet your loved one's needs, size, color and style.

The DID is the rough look into what is to be designed in accordance with the customer's input.

The DSD is being precise with the customer's input based on the company's engineering capabilities.

Advantages and disadvantages of DSD and DID may not be compared as they are made to serve different company operational needs.

Well one is necessary for the other. I don't know if I would talk about them in terms of pros and cons. One document is necessary for the other. Let's stick with the door knob example. You need a basic understanding of what is wanted. That's what the DID document is for. An understanding of what is needed is formulated in this document. If you get down to the details, like in the DSD, you may constrain yourself too much too quickly. Knowing the generic needs allow for easy change later. You can work off the DID. If you start with the DSD, and then you need to make a change, you don't know what aspect of the DSD was required. Then you have to go back and waste time checking what would be in the DID.

Advantages of the DID document would be to have a general understanding of what the product is going to look like. This is basically a mental picture of what you and the department will believe the design is going to be. With a DSD, this will be more specifically what the idea will become. With design specifications, you can decide what kind of red you want the knob to be and what size is best for the product. The disadvantages of a DID would be that it’s not specific enough so when one person thinks of the general idea, it could mean something else is someone else’s eyes. The disadvantages of a DSD would be that with specific descriptions, it can become more difficult to make the product. I believe they go hand in hand, where you have a general idea and you make it happen with specific features. Both these documents will provide different needs for the product and are both beneficial at different stages of the product.

I agree with the DID as being a rough blueprint to the customers input as @amd29 had stated. The example I disagree with because it does not compare to medical devices since their tends to be more regulations and scientific attributes associated with the field. The example is more for an interior designer then a engineer.
To answer more on the DSD it’s the engineers job to take what management gives them and to put it into the language of the engineer which is more technical and analytical. I find it challenging to filter what people want based off minimal exposure to the customer. That’s why I believe engineers should also speak with customers not just marketing.

I believe they are both necessary because they help you take action. These documents basically tell you what you will be building. With these documents technically anyone should be able to build your product. They both work off each other as was stated the DID is just a broad description so they are not any numbers or specifications. The DSD has all the numbers and the specifications. But you cannot have a DSD without a DID. They are both really helpful because as I stated the words in these documents will lead you to the actions you need to make the product. For example “red knob, 3-cm in diameter, dyed with Red #5 from Vendor X or Vendor Y” this statement from a DSD tells you the exact color and size of the knob and it also tells you where it will be going. With these words you can take action and being to build your product.

Advantages of DID is that serves as an overall/general description of the product it also states the design input as clear and objective without numerical specifications. The major disadvantage with DID is that it's too broad. Meanwhile, DSD captures numerical specifications that will serve as the foundation for the user requirement document. A disadvantage of DSD is that it can take a while to develop because it must ensure that specifications are appropriate and that they address the intended use of the device or product. However, both of them are important because they state all functional, performance, safety, and regulatory requirements.

I think the need or the advantage of the DID and DSD is that they serve two different audience. DID, which contains the broad specifications, is great for the customers, the ones who are actually interested in buying the product. It is also good for project managers, to review the market needs and the importance of such a product. This audience doesn't need to see or know the exact specifics of dimension, color, etc. Just the overall purpose and design of the product.

The DSD on the other hand, contains the highly detailed specifications, this is needed for the internal team of research and engineers. It helps them design the product well, having every aspect specified. It also helps during testing and risk management. The DID can't be used for such significant development and testing.

The DID document is a very rough sketch. When anyone looks at it, they should be able to tell what it is even though there aren't many details. This sort of document is great for customers who don't really understand the specifics of everything that can goes on. The DSD is the Mona Lisa of the document. You add in all the details and those that can read and understand what is going on should be able to picture exactly what it will look like and should be able to recreate it themselves and have it be an exact copy of the product. This is meant more for the team that is producing the product so they know exactly what it is the customer wants for the product and are able to meet the customers needs and make any necessary changes much more easily.

I agree with all of you guys on the difference you mentioned about DID and DSD. we can consider it a high and low block diagrams. One present the idea in a simple way that any audience can understand the main concept of the product like the DID and the other one should all the technical details for the same project in a very engineering detailed oriented document like the DSD. Also, it's not only in product management document also in production. it is very similar to the difference between SOP and BOM list, SOP has less information about the product VS the BOM list has all the detail for each component in the product.

The DID and DSD are both necessary in their own right as they can be meant for different audiences and purposes. DID's basically outline the high level overview of what the product is going to be like: red, can make sounds, light enough to hold, etc. For those levels of people involved with products who only have time/bandwidth to care about the high level details such as management, this is the document that they see, or at least some form of it (whether or not it is processed into even higher level form is another story). However, a document like this is not specific enough for it to manifest as a product. It does not answer the facets of how: how much, how little, how accurate, etc. That is where the DSD comes in, providing the most technical detail of the product. If it is considered in the design, it must be spelled out in the DSD. This is more useful to those manufacturing and designing the project, as their scope is much deeper within this product. If you were to hand each document to the other party, (DID to engineer, DSD to management) then there would be an uproar: management does not need such a technical document (and may not have the deep technical expertise/product knowledge to know how to decipher the document) in order to make calls on it. Engineers cannot design or manufacture a product without details; with such nebulous understanding of the details, a consistent product outcome is not able to be achieved. So each document is necessary in order to speak to the different people involved with the project.

I must agree with most of the discussion points mentioned above, but I would like to point out that for an engineer, the DSD would be a must-read document, as we don’t rely on broad descriptions. For example, an engineer will not only tell a certain device works with a 110-volts or 220-volts, but rather would tell you the polarity and amperage. Similarly, a computer engineer would check the compatibility of a piece of hardware before connecting it to the machine. While the DID would be a quick general label that would inform the user about the device, the user would need more explanation regarding the product. Which is why the DSD is very important as it might contain drawings or sketches that would inform the user of all common possibilities that arise when the device is used. It might also contain some suggestions on troubleshooting steps to be taken if a certain problem occurs. It might also demonstrate to the user how a certain calibration process can be performed. Clearly, a good designer must include crystal clear DID and DSD. In a way, the DID and the DSD complement each other, as every point mentioned in the DID must be discussed and explained in details in the DSD. In addition, all of the specifications in the DSD must be verified through carefully conducted experiments.

DID and DSD are both important documents because they provide the customer intended design and the design feature specification. The DID document gives an insight to what the customer wants, the document shows what the product will look like. It will not show what the dimensions of the feature used in creating the design, this where DSD help. DSD document shows the schematics, which helps the manufacture group in creating the design. Without these document the customer will not know if design discrpition is met, the customer must see if it is the end product they want, and must have the dimension in order to be created.

The Design Input Document (DID) and Design Specification Document (DSD) are very similar, but I think they belong to distinctly different steps in the product development life cycle. The DID is meant to be just the big picture type of document where the marketing department goes out and does research to find a market gap or surveys medical professionals and determines the basic customer needs for a new product. These are general requirements and are sort of just like a brainstorming session where you get all of your ideas on the table. The DSD is where the engineering department comes in and determines what is actually possible given current technology and resources, and designs the detailed specification for the product. The information in the documents is the same, but it is prepared by two totally different departments of vastly different expertise. Both are useful in visualizing the product, but one is a means to create the other.

Both documents are necessary because they are used to describe the product in the two major ways you can describe anything: qualitatively and quantitatively. The DID is the document in which the writer can briefly describe the essential features of the product so that the reader can have a more intuitive way of understanding the device. In this document, you can describe how the product looks to you as the viewer and what the main features and capabilities are. The DSD describes the product using quantitative information. In other words, you use numbers to describe your product by reporting measurements and any accompanying errors concerning the medical device. The main advantage to using a DSD is that it gives numerical data on essential features of the product such as the dimensions so you can imagine what the product looks like and how it performs. A DID document will not report on how well the product performs but it gives the reader a different perspective because you can describe what the product does without giving a dry description as well as the aesthetics of the product.