My usual not-very-useful answer is that HLD and LLD are whatever you say they are. You need to know who will read the design and what they need to learn from them. Sometimes nobody reads them ... all the value is in the mental process of making them. Then you can tailor the artifacts to the audience, or maybe decide not to do them at all.
One distinction some people use is a HLD that is language, OS, and perhaps even architcture-free. A LLD introduces those things. Look for the different models in Model Driven Architecture (MDA) for better definitions.
Is somebody asking you for two sets of design docs or something?
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi
Joined: Jan 12, 2002
Hi, Thanks for the reply.I have to create these two docs soon, so iam trying to get an idea abt these.
What do you have to create them for? If you provide us more context, we are more likely able to help you...
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus
Joined: Jan 29, 2003
This may get you some dirty looks, but can you challenge the people who want the docs to tell you what they use them for, what they need to do their jobs? It's a long and sad road to guess, get lots of complaints, guess again, get lots of complaints, etc. The best news is when you find somebody who'd be happier to have you come by and spend an hour talking at the white board and skip writing the doc altogether. He learns more and so do you!
I've given up on docs but I write tons of documentation in a web site (Wiki). A reader can follow a function through the architecture from end to end, browse many functions in the same level of abstraction, follow links up for an overview or down for details. A Word doc with a hierarchical table of contents is too hard for me any more.