C++: Implementing Design by Contract to reduce bugs

Grok Headline matches for C++: Implementing Design by Contract to reduce bugs

Reduce Redundancy: Decrease Duplicated
Design Decisions

Reduce Redundancy: Decrease Duplicated
Design Decisions 06/12/2002 09:17 AM
User interface complexity increases when a single feature or hypertext link is presented in multiple ways. Users rarely understand duplicates as such, and often waste time repeating efforts or visiting the same page twice by mistake. -- Jakob Nielsen

"zeldman.juanita"

Former FDA Regional Director Joins
Medical Device Contract Design Company

Former FDA Regional Director Joins
Medical Device Contract Design Company 04/18/2005 02:42 AM
Summa Design, a contract design and development company focused on the medical device industry, announced today that Dudley Harris, a former Regional Director for the FDA, has joined Summa Design as Director of Regulatory Affairs and Quality Systems. [PRWEB Apr 18, 2005]

Tender: Small Business Service offers
internet creative design contract

Tender: Small Business Service offers
internet creative design contract 07/12/2004 02:32 AM
PublicTechnology.net Jul 12 2004 7:16AM GMT

Re: (IE/SCOB) Switching Software Because
of Bugs: Some Facts About Software and
Security bugs

Re: (IE/SCOB) Switching Software Because
of Bugs: Some Facts About Software and
Security bugs 07/07/2004 02:41 PM
Thomas C. Greene (Jul 06 2004)

(IE/SCOB) Switching Software Because of
Bugs: Some Facts About Software and
Security bugs

(IE/SCOB) Switching Software Because of
Bugs: Some Facts About Software and
Security bugs 07/01/2004 10:30 AM
Drew Copley (Jun 30 2004)

Jacob Cane Design – Website Design and
Graphic Design services ...

Jacob Cane Design – Website Design and
Graphic Design services ... 03/06/2004 02:00 AM
Feb 26, 2004(PRWEB) February 26, 2004--Web Development: We use the best combination of all the tools available for web design, including Flash, JavaScript, PHP/MySQL, CSS ...

Implementing CSS (Part 1)

Implementing CSS (Part 1) 06/05/2005 11:17 PM

One of the most interesting problems (to me at least) in browser layout engines is how to implement a style system that can determine the style information for elements on a page efficiently. I worked on this extensively in the Gecko layout engine during my time at AOL and I've also done a lot of work on it for WebCore at Apple. My ideal implementation would actually be a hybrid of the two systems, since some of the optimizations I've done exist only in one engine or the other.

When dealing with style information like font size or text color, you have both the concept of back end information, what was specified in the style rule, and the concept of front end information, the computed result that you'll actually use when rendering. The interesting problem is how to compute this front end information for a given element efficiently.

Back end information can be specified in two different ways. It can either be specified using CSS syntax, whether in a stylesheet or in an inline style attribute on the element itself, or it is implicitly present because another attribute on the element specified presentational information. An example of such an attribute would be the color attribute on the font tag. Both WebCore and Gecko use the term mapped attribute to describe an attribute whose value (or even mere presence) maps to some implicit style declaration.

A rule in CSS consists of two pieces. There is the selector, that bit of information that says under what conditions the rule should match a given element, and there is the declaration, a list of property/value pairs that should be applied to the element should the selector be matched.

All back end information can ultimately be thought of as supplying a declaration. A normal rule in a stylesheet that is matched has the declaration specified as part of the rule. An inline style attribute on an element has no selector and is simply a declaration that always applies to that element. Similarly each individual mapped attribute (like the color and face attributes on the font tag) can be thought of as supplying a declaration as well.

Therefore the process of computing the style information for an element can be broken down into two phases. The first phase is to determine what set of declarations apply to an element. Once that back end information has been determined, the second phase is to take that back end information and quickly determine the information that should be used when rendering.

WebCore (in upcoming Safari releases) has a really cool optimization that I came up with to avoid even having to compute the set of declarations that apply to an element. This optimization in practice results in not even having to match style for about 60% of the elements on your page.

The idea behind the optimization is to recognize when two elements in a page are going to have the same style through DOM (and other state) inspection and to simply share the front end style information between those two elements whenever possible.

There are a number of conditions that must be met in order for this sharing to be possible:
(1) The elements must be in the same mouse state (e.g., one can't be in :hover while the other isn't)
(2) Neither element should have an id
(3) The tag names should match
(4) The class attributes should match
(5) The set of mapped attributes must be identical
(6) The link states must match
(7) The focus states must match
(8) Neither element should be affected by attribute selectors, where affected is defined as having any selector match that uses an attribute selector in any position within the selector at all
(9) There must be no inline style attribute on the elements
(10) There must be no sibling selectors in use at all. WebCore simply throws a global switch when any sibling selector is encountered and disables style sharing for the entire document when they are present. This includes the + selector and selectors like :first-child and :last-child.

The algorithm to locate a shared style then goes something like this. You walk through your previous siblings and for each one see if the above 10 conditions are met. If you find a match, then simply share your style information with the other element. Such a system obviously assumes a reference counting model for your front end style information.

Where this optimization kicks into high gear, however, is that it doesn't have to give up if no siblings can be located. Because the detection of identical style contexts is essentially O(1), nothing more than a straight pointer comparison, you can easily look for cousins of your element and still share style with those elements.

The way this works is that if you can't locate a sibling, you can go up to a parent element and attempt to find a sibling or cousin of the parent element that has the same style pointer. If you find such an element, you can then drill back down into its children and attempt to find a match.

This means that for HTML like the following:

<table>
<tr class='row'>
<td class='cell' width=300 nowrap>Cell One</td>
</tr>
<tr class='row'>
<td class='cell' width=300 nowrap>Cell Two</td>
</tr>

In the above example, not only do the two rows share the same style information, but the two cells do as well. This optimization works extremely well for both old-school HTML (in which many deprecated presentational tags are used) and newer HTML (in which class attributes might figure more prominently).

Once the engine determines that a style can't be shared, i.e., that no pre-existing front end style pointer is available, then it's time to figure out the set of declarations that match a given element. It is obvious that for inline style attributes and mapped attributes that you can find the corresponding declaration quickly. The inline style declaration can be owned by the element, and the mapped attributes can be kept in a document-level hash. WebCore has a bit of an edge over Gecko here in that it treats each individual mapped attribute on an element as a separate declaration, whereas Gecko hashes all of the mapped attributes on an element as a single "rule." This means that Gecko will not be able to share the mapped attribute declaration for the following two elements:

<img width=300 border=0>
<img width=500 border=0>

WebCore creates three unique declarations and hashes them, one for a width of 300, one for a width of 500, and one for a border of 0. Gecko creates two different "rules," one for (width=300,border=0) and another for (width=500,border=0). As you can see in such a system, you will frequently not be able to treat the identical border attributes as the same.

Aside from this difference in mapped attribute handling, the two engines employ a similar optimization for quickly determining matching stylesheet rules called rule filtering. All rules that are potentially matchable by any element (i.e., that have the correct media type) are hashed based on the contents of the rightmost simple selector in the rule.

A selector in CSS can be either simple (meaning that all of the contents of that selector apply only to a single element) or compound (meaning that you may examine multiple elements like parents or siblings of that element). A compound selector is essentially a chain of simple selectors, so the following rule:

tr > td { color: blue }

has two simple selectors, tr and td. The rightmost simple selector in the rule is the one that we will use for the rule filtering optimization.

The rightmost simple selector falls into four categories.

(1) The selector uses an ID. (Example: #foo)
(2) The selector doesn't have an ID but uses a class. (Example: .foo)
(3) The selector has no class or ID but specifies a tag name. (Example: div)
(4) The selector specifies none of these things. (Example: *[disabled])

The rule is placed into one of four hashtables depending on which category it falls into. The idea behind these categorizations is to always filter out more specific information first. For example, if an element has a specific ID, then obviously any rules whose rightmost selector uses a different ID cannot match. Technically the last category can just be a list and not a hashtable, since those rules must always be examined by all elements.

Each hashtable, therefore, consists of a mapping from a given atomic string to a set of rules that match. The class attribute is exceptional in that you must put the rule into the hashtable multiple times if multiple class attributes are used.

When determining the set of rules that match a given element, you only examine rules that correspond to the correct hash entry based off your ID, classes and tag name. This optimization basically eliminates 95+% of the rules up front so that they need not even be considered during the matching process.

Each rule is then examined in detail, with all selectors being checked, to determine if it is a match, and the set of matches is collected. The set of matches can then be sorted by priority and specificity such that all the declarations are in the proper application order.

This brings us to the final phase of the style computation, which is taking the set of matches and quickly computing the appropriate front end style information. It is here that Gecko really shines. What I implemented in Gecko was a data structure called the rule tree for efficient storing of cached style information that can be shared *even when* two elements are not necessarily the same.

The idea behind the rule tree is as follows. You can think of the universe of possible rules in your document as an alphabet and the set of rules that are matched by an element as a given input word. For example, imagine that you had 26 rules in a stylesheet and you labeled them A-Z. One element might match three rules in the sheet, thus forming the input word "C-A-T" or another might form the input word "D-O-G."

There are several important observations one can make once you formulate the problem this way. The first is that words that are prefixes of a larger word will end up applying the same set of rules. All additional letters in the word do is result in the application of more declarations. Thus the rule tree is effectively a lexicographic tree of nodes, with each node in a tree being created lazily as you walk the tree spelling out a given word.

This system allows you to cache style information at each node in the tree. This means that once you've looked up the word "C-A-T-E-R-W-A-U-L", and cached information at all of the nodes, then looking up the word "C-A-T" becomes more efficient.

In order to make the caching efficient, properties can be grouped into categories, with the primary criterion for categorization being whether the property inherits by default. It's also important to group properties together that would logically be specified together, so that when a fault occurs and you have to make a copy of a given struct, you do so knowing that the other values in the struct were probably going to be different anyway.

Once you have the properties grouped into categories like the border struct or the background struct, then you can either store these structs in the rule tree or as part of a style tree that more or less matches the structure of the document. Inheritance has to apply down the style tree and tends to force a fault, whereas non-inherited properties can usually be cached in the rule tree for easy access.

WebCore doesn't contain a rule tree, but it is smart enough to refcount the structs and share them as long as no properties have been set in the struct. In practice this works pretty well but is not as ideal as the rule tree solution.

Implementing XHTML 2.0

Implementing XHTML 2.0 07/27/2004 08:02 PM
Well, I slept off most of my desire to blog about XHTML 2.0, but here's a post anyway. The thing is, I don't think implementing elements using behaviors is really a good idea, although I feel bad saying it while the W3C is linking to my test implementation. ?

Implementing An ADO Data Control With
VB6

Implementing An ADO Data Control With
VB6 06/18/2002 10:19 AM
The ADO data control can save Visual Basic developers hours of time. In this article Susan shows us exactly how to go about implementing an ADO control. 5 Free Bonuses!!! "Attention All Web Developers" Now includes 5 FREE eBooks to help you promote your ConMan website! "This is one of the best pieces of software that we have ever used. It's quick, streamlined, and allowed us to have a fully working site packed with articles in just 3 hours" Ever wanted to run your own content driven web site? Well now you can with ConMan: the fast, flexible and secure web site + admin suite. Try it for free!Click here. Get notified when we post new content: New Forum Threads 1. How do i do this? 2. C# editor of your choice? 3. Article Added Date 4. ASP Developer Seeking Employment 5. Hlp pls. - 1 record per page, refresh through records problem 6. your site was down :( 7. Can't get html editor to work properly 8. New website & advice 9. mysql tables 10. Article Type More Forum Threads... Other Recent Articles An Introduction To The Bulk Copy Utility // by Mitchell Harper - 12th Jun 2002

Implementing filesystems in Python

Implementing filesystems in Python 12/10/2003 06:35 PM

LUFS-Python provides a relatively simple API for implementing new Linux filesystems in pure Python. You install the package, write a class implementing methods for handling filesystem operations such as creating a directory, opening/reading/writing/closing a file, creating symlinks etc and finally mount your new filesystem with some special arguments to the mount command.

At first glance, this is a bit of a gimmick - why would you want to write your own filesystem in the first place? We've been talking about this at work and came up with a few ideas. How about a filesystem where HTML files saved in a certain directory were instantly run through HTMLTidy and converted in to valid XHTML ? Or a custom network filesystem that saves files on a remote server using GnuPG to encrypt them before transfer? How about a read-only filesystem that lets you browse the contents of a MySQL database? Just imagine being able to use tools such as grep and find to search your database. A module that maps someone elses public web server to your own filesystem, making mirroring as easy as running a recursive cp command. A filesystem that updates a swish-e full-text index every time a file is saved to it - years before Microsoft release Longhorn. The possibilities are endless.

Here's a really fun idea: a filesystem that implements a dynamic website. Instead of using tools like mod_python to dynamically create pages, implement a filesystem that dynamically creates HTML files as they are requested and set up a stock Apache install with the dynamic filesystem as the document root. Then point ProFTPD at it so you can log in via FTP and mess with your content dynamically. We're thinking about bulding an FTP interface to our new database driven CMS, but we could just build a filesystem interface and point our FTP server straight at it.

I'm sure there are performance and stability issues that make most of the above more trouble than it's worth, but I think you'll agree it's a pretty exciting technology.

Implementing Flood Control

Implementing Flood Control 12/19/2004 03:27 PM
If the load of application relies on incoming events, you may eventually face the happy curse of popularity: too much work to do with your available resources. If you set a limit on how many events you can process within a time period, you can avoid the flood. Vladi Belperchinov-Shabanski explains the algorithm and demonstrates working code.

Implementing client-side code for SSL in
JDK 1.3

Implementing client-side code for SSL in
JDK 1.3 01/23/2003 02:47 AM
CNET Jan 23 2003 1:24AM ET

Implementing a relational database using
MySQL

Implementing a relational database using
MySQL 04/06/2005 12:17 PM
When properly implemented, a relational database can greatly enhance the availability of data and information for an enterprise's decision makers. However, deploying a relational database on almost any scale requires a thorough understanding of the fundamental concepts and rules that govern their behavior.

Poll Position: Implementing Identity

Poll Position: Implementing Identity 04/04/2005 06:03 AM
Q: How do you best build a brand?

Hands On: Implementing OS X 10.3
(Panther) Server

Hands On: Implementing OS X 10.3
(Panther) Server 02/10/2004 02:43 AM
I can tell you now that everything Apple promised is indeed in there -- and it works! By Yuval Kossovsky (Computerworld via MyAppleMenu)

Implementing Linux emulation on NetBSD

Implementing Linux emulation on NetBSD 05/13/2004 03:28 AM
NetBSD's Linux emulation doesn't run a Linux kernel on a virtual machine; it runs Linux binaries on a NetBSD kernel. Linux emulation let you run plenty of useful programs that won't run natively under NetBSD, such as Sun's 1.4 Java Runtime Environment and JDK.

ICANN To Begin Implementing IPv6

ICANN To Begin Implementing IPv6 07/22/2004 02:58 PM
WebProNews Jul 22 2004 6:18PM GMT

Gov't could raise P20B by implementing
IP law

Gov't could raise P20B by implementing
IP law 09/14/2004 04:18 PM
Sun Star Network Sep 14 2004 7:26PM GMT

Implementing XPath for wireless devices
(XML.org)

Implementing XPath for wireless devices
(XML.org) 06/07/2002 08:34 AM

Implementing XPath for Wireless Devices

Implementing XPath for Wireless Devices 06/06/2002 05:37 PM
In the first of a two-part series, we explore the implementation of XPath on wireless devices using the WAP family of standards.

Being User-Centered When Implementing a
UCD Process

Being User-Centered When Implementing a
UCD Process 09/09/2002 06:29 AM

"Code snippets for implementing tags
with SQL"

"Code snippets for implementing tags
with SQL" 04/11/2005 11:43 PM

Software Developer resist implementing
Atom

Software Developer resist implementing
Atom 05/24/2004 07:44 AM

Not all developers who are designing RSS applications are adding Atom support and I can't say that I blame them but it is interesting to see their comments. [miseldine.com]

Implementing successful shared services
in government

Implementing successful shared services
in government 02/17/2004 10:26 PM
Computer Weekly Feb 18 2004 2:09AM GMT

Scilly Isles looks at implementing
e-government across 5 islands

Scilly Isles looks at implementing
e-government across 5 islands 04/16/2005 02:13 AM
PublicTechnology.net Apr 16 2005 4:16AM GMT

Implementing XPath for Wireless Devices,
Part II

Implementing XPath for Wireless Devices,
Part II 07/17/2002 07:16 PM
In the second of a two-part series, we explore the implementation of XPath on wireless devices using the WAP family of standards.

Implementing XPath for wireless devices,
part II (XML.com)

Implementing XPath for wireless devices,
part II (XML.com) 07/18/2002 07:34 PM

Guidelines for Implementing and
Maintaining Virtual Reference Services

Guidelines for Implementing and
Maintaining Virtual Reference Services 07/29/2004 06:48 AM
Guidelines for Implementing and Maintaining Virtual Reference Services
http://www.ala.org/ala/rusa/rusaprotools/referenceguide /virtrefguidelines.htm

The purpose of these guidelines is to assist libraries and consortia with implementing and maintaining virtual reference services. The guidelines are meant to provide direction, without being over- prescriptive. Variance among institutions will result in differences in the adherence to these guidelines, but the committee hopes to have cast the model broadly enough to provide a framework for virtual reference which can be widely adopted and which will endure through many changes in the ways in which libraries provide virtual reference services. Prepared by the MARS Digital Reference Guidelines Ad Hoc Committee, Reference and User Services Association, 2004. Approved by the RUSA Board of Directors June 2004.

Sakhr implementing solutions with
e-government project in Qatar

Sakhr implementing solutions with
e-government project in Qatar 03/27/2005 07:47 AM
AME Info Mar 27 2005 9:54AM GMT

Features: Implementing REST Web
Services: Best Practices and Guidelines

Features: Implementing REST Web
Services: Best Practices and Guidelines 08/11/2004 07:03 PM
Hao He offers guidelines and best practices for implementing REST web services.

Enterprise Java Beans - Part 2,
Implementing Your First EJBs

Enterprise Java Beans - Part 2,
Implementing Your First EJBs 11/14/2003 03:33 AM
WebmasterBase Nov 14 2003 2:36AM ET

TechRepublic: Building and Implementing
a Successful Information Security Policy

TechRepublic: Building and Implementing
a Successful Information Security Policy 12/09/2003 01:27 PM
ZDNet Dec 9 2003 12:53PM ET

AHEADOFMYTIME.COM and Right Brain Design
Group Form Website Design and
Development Alliance

AHEADOFMYTIME.COM and Right Brain Design
Group Form Website Design and
Development Alliance 08/10/2004 03:51 AM
AHEADOFMYTIME.COM and Right Brain Design Group, both long time Chicago based marketing agencies team up to provide innovative approach to web site design and internet marketing. [PRWEB Aug 10, 2004]

IBM, Intel Open BladeCenter Design
Specifications; Companies Simplify
Server Design

IBM, Intel Open BladeCenter Design
Specifications; Companies Simplify
Server Design 09/02/2004 03:45 PM
Linux Electrons Sep 2 2004 7:41PM GMT

The mid-sized 7E7, being tweaked and
simulated in Boeing design labs and
three-dimensional computer design ima

The mid-sized 7E7, being tweaked and
simulated in Boeing design labs and
three-dimensional computer design ima 05/23/2004 07:43 PM
MSNBC May 23 2004 10:15PM GMT

Designing for Real People: Additional
Lessons for Web Design from Mall and
Retail Design

Designing for Real People: Additional
Lessons for Web Design from Mall and
Retail Design 10/01/2002 09:17 AM

Introducing the Band of Gonzos Web
Design and SEO Forum: Website Design
Contest

Introducing the Band of Gonzos Web
Design and SEO Forum: Website Design
Contest 06/15/2004 02:12 AM
We invite entries for a basic website design with navigation for a hosting company website (OgreHosting.com). The winning design will incorporate the existing graphics/logos and the general theme of OgreHosting. [PRWEB Jun 15, 2004]

Design Intuition 1.3: 3-D CAD Software
Makes Woodworking And Design Projects
Easy

Design Intuition 1.3: 3-D CAD Software
Makes Woodworking And Design Projects
Easy 09/14/2004 10:45 AM
Design Intuition 1.3 is easy and fun, as well as a great value. I recommend it for woodworkers, cabinetmakers, and kitchen designers. By Greg Miller, Macworld (via MyAppleMenu)

Online School of Design, Sessions,
Announces Latest Design Competition for
Not-for-Profit Organizations

Online School of Design, Sessions,
Announces Latest Design Competition for
Not-for-Profit Organizations 06/06/2005 12:02 AM
NPower is the latest participant in online design school's innovative Design Competition Program in line with mission of “preparing design professionals”. [PRWEB Jun 3, 2005]
Grok Description matches for C++: Implementing Design by Contract to reduce bugs
GrokA matches for C++: Implementing Design by Contract to reduce bugs

C++: Implementing Design by Contract to reduce bugs

The following phrases have been identified by the grok system as matching this entry: