# Maisqual Metrics

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 Revision as of 11:29, 6 March 2014 (view source) (→Availability of metrics)← Older edit Revision as of 11:37, 6 March 2014 (view source) (→Availability of metrics)Newer edit → Line 56: Line 56: |- |- | style="text-align:left" | Effective lines of code || ELOC || X  || X || X | style="text-align:left" | Effective lines of code || ELOC || X  || X || X - |} + |- + | style="text-align:left" | Source lines of code || SLOC || X  || X || X + |- + | style="text-align:left" | Line Count || LC || X  || X || X + |- + | style="text-align:left" | Mixed lines of code || MLOC || X  || X || X + |- + | style="text-align:left" | Comment lines of code || CLOC || X  || X || X + |- style="background-color: #CCCCFF" + | style="text-align:left" | Miscellaneous || Mnemo || Appli. || File || Func. + |- + | style="text-align:left" | Non conformities count || NCC || X || X || X + |- + | style="text-align:left" | Comment rate || COMR || X || X || X + |- + | style="text-align:left" | Number of statements || STAT || X || X || X + + |- style="background-color: #CCCCFF" + | style="text-align:left" | Control flow complexity metrics || Mnemo || Appli. || File || Func. + |- + | style="text-align:left" | Non conformities count || NCC || X || X || X + |- + | style="text-align:left" | Comment rate || COMR || X || X || X + |- + | style="text-align:left" | Number of statements || STAT || X || X || X + |- style="background-color: #CCCCFF" + | style="text-align:left" | Miscellaneous || Mnemo || Appli. || File || Func. + |- + | style="text-align:left" | Maximum nesting level || NEST || || || X + |- + | style="text-align:left" | Number of Paths || NPAT || || || X + |- + | style="text-align:left" | Cyclomatic number || VG || X || X || X + |- + | style="text-align:left" | Control flow tokens || CFT || X || X || X + |- style="background-color: #CCCCFF" + | style="text-align:left" | Halstead metrics || Mnemo || Appli. || File || Func. + |- + | style="text-align:left" | Total number of operators || TOPT || || || X + |- + | style="text-align:left" | Number of distinct operators || DOPT || || || X + |- + | style="text-align:left" | Total number of operand || TOPD || || || X + |- + | style="text-align:left" | Number of distinct operands || DOPD || || || X + |}

## Revision as of 11:37, 6 March 2014

This page lists the metrics retrieved for the different analyses performed on projects.

# Availability of metrics

The set of available metrics depends on the type of artefact (e.g. application, file, function) and data set (weekly, releases, version), and on the characteristics of the project (e.g. object-oriented).

 Source Code SCM COM Common OO Diff. Total Time Time Java Evolution X X X X X X Java Releases X X X X Java Versions X X X C Evolution X X X X X C Releases X X X C Versions X X

Some metrics are only available for specific contexts, like the number of classes for object-oriented programming. Metrics available for each type of data set are described in the table above. Object-Oriented metrics are CLAS (number of classes defined in the artefact) and DITM (Depth of Inheritance Tree). Diff metrics are LADD, LMOD, LREM (Number of lines added, modified and removed since the last analysis). Time metrics for SCM are SCM_*_1W, SCM_*_1M, AND SCM_*_3M. Total metrics for SCM are SCM_COMMITS_TOTAL, SCM_COMMITTERS_TOTAL, SCM_COMMITS_FILES_TOTAL and scm_fixes_total. Time metrics for Communication are COM_*_1W, COM_*_1M, and COM_*_3M.

Metrics defined on a lower level (e.g. function) can be aggregated to upper level in a smart manner: as an example, the cyclomatic number at the file level is the overall sum of its function’s cyclomatic numbers. The meaning of the upper-level metric shall be interpreted with this fact in mind, since it may introduce a bias (also known as the Ecological fallacy[1]). When needed, the smart manner used to aggregate information at upper levels is described hereafter.

 Artefact Counting metrics Mnemo Appli. File Func. Number of files FILE X Number of functions FUNC X X Line Counting metrics Mnemo Appli. File Func. Lines of braces BRAC X X X Blank lines BLAN X X X Effective lines of code ELOC X X X Source lines of code SLOC X X X Line Count LC X X X Mixed lines of code MLOC X X X Comment lines of code CLOC X X X Miscellaneous Mnemo Appli. File Func. Non conformities count NCC X X X Comment rate COMR X X X Number of statements STAT X X X Control flow complexity metrics Mnemo Appli. File Func. Non conformities count NCC X X X Comment rate COMR X X X Number of statements STAT X X X Miscellaneous Mnemo Appli. File Func. Maximum nesting level NEST X Number of Paths NPAT X Cyclomatic number VG X X X Control flow tokens CFT X X X Halstead metrics Mnemo Appli. File Func. Total number of operators TOPT X Number of distinct operators DOPT X Total number of operand TOPD X Number of distinct operands DOPD X

All data sets are structured in three files, corresponding to the different artefact types that were investigated: application, file and function.

# Source code metrics

These metrics are computed on the source code of projects by the SQuORE analyser. Releases data sets are extracted from the compressed source tarbals directly downloaded from the official location on the project web site. All other types of data sets are extracted from software configuration management repositories (either CVS, Subversion or Git).

Artefact counting metrics

Artefact counting metrics include the number of files and number of functions.

• The number of files (FILE) counts the number of source files in the project, i.e. which have an extension corresponding to the defined language (.java for Java or .c and .h files for C).
• The number of functions (FUNC) sums up the number of methods or functions recursively defined in the artefact.

Line counting metrics

Line counting metrics propose a variety of different means to grasp the size of code from different perspectives. It includes STAT, SLOC, ELOC, CLOC, MLOC, and BRAC.

• The number of statements (STAT) counts the total number of instructions. Examples of instructions include control-flow tokens, plus else, cases, and assignments.
• Source lines of code (SLOC) is the number of non-blank and non-comment lines in code.
• Effective lines of code (ELOC) also removes the number of lines that contain only braces.
• Comment lines of code (CLOC) counts the number of lines that include a comment in the artefact. If a line includes both code and comment, it will be counted in SLOC, CLOC and MLOC metrics.

Control flow complexity metrics

• The maximum nesting level (NEST) counts the highest number of imbricated code (including conditions and loops) in a function. Deeper nesting threatens understandability of code and induces more test cases to run the different branches. Practitioners usually consider that a function with three or more nested levels becomes significantly more difficult for the human mind to apprehend how it works.
• The number of execution paths (NPAT) is an estimate of the possible execution paths in a function. Higher values induce more test cases to test all possible ways the function can execute depending on its parameters. An infinite number of execution paths typically indicates that some combination of parameters may cause an infinite loop during execution.
• The cyclomatic number (VG), a measure borrowed from graph theory and introduced by McCabe[2] is the number of linearly independent paths that comprise the program. To have good testability and maintainability, McCabe recommends that no program modules (or functions as for Java) should exceed a cyclomatic number of 10. It is primarily defined at the function level and is summed up for higher levels of artefacts.
• The number of control-flow tokens (CFT) counts the number of control-flow oriented operators (e.g. if, while, for, switch, throw, return, ternary operators, blocks of execution). else and case are typically considered a part of respectively if and switch and are not counted.

The control flow graph of a function visually plots all paths available when executing it. Examples of control flow are provided in figure 6.1; figures 6.1a and 6.1b shows two Java examples on Ant (the code of these functions is reproduced in appendix D.1 page 267 for reference) and figure 6.1c shows a C example extracted from GCC. But control flows can be a lot more complex, as exemplified in figure 6.1d for an industrial application.

Halstead metrics

Halstead proposed in his Elements of Software Science[3] a set of metrics to estimate some important characteristics of a software. He starts by defining 4 base measures:

• the number of distinct operands (DOPD, or n2 ),
• the number of distinct operators (DOPT, or n1 ),
• the total number of operands (TOPD, or N2 ), and
• the total number of operators (TOPT, or N1 ).

Together they constitute the following higher-level derived metrics:

• program vocabulary: n = n1 + n2,
• program length: N = N1 + N2,
• program difficulty: $D = \frac{n_1}{2} \times \frac{N_2}{n_2}$
• program volume: V = Nlog 2(n),
• estimated effort needed for program comprehension: $E = D \times V$ ,
• estimated number of delivered bugs: $B = \frac{E^{2/3}}{3000}$

In the data sets, only the four base measures are retrieved: DOPD, DOPT, TOPD, and TOPT. Derived measures are not provided in the data sets since they can all be computed from the provided base measures.

Rules-oriented measures

• NCC is the number of non-conformities detected on an artefact. From the practices perspective, it sums the number of times all rules have been transgressed on the artefact (application, file or function).
• The rate of acquired practices (ROKR) is the number of respected rules (i.e. with no violation detected on the artefact) divided by the total number of rules defined for the run. It shows the number of acquired practices with regards to the full rule set.

Differential measures

Differential measures are only available for evolution and release data sets. They quantify the number of lines added (ladd), modified (lmod) or removed (lrem) since the last analysis, be it a week (for evolution data sets) or a random delay between two releases (which varies from one week to one year). They give an idea about the volume of changes (either bug fixes or new features) that occured between two releases. In the case of large refactoring, or between major releases, there may be a massive number of lines modified, whereas only small increments may be displayed for more agile-like, often-released projects (e.g. Jenkins).

Object-oriented measures

Three measures are only available for object-oriented code. They are the number of classes (CLAS), the maximum depth of inheritance tree (DITM), and the above-mentionned rate of acquired rules (ROKR).

• The number of classes (CLAS) sums up the number of classes defined in the artefact and its sub-defined artefacts. One file may include several classes, and in Java anonymous classes may be included in functions.
• The maximum depth of inheritance tree (DITM) of a class within the inheritance hierarchy is defined as the maximum length from the considered class to the root of the class hierarchy tree and is measured by the number of ancestor classes. In cases involving multiple inheritance, the ditm is the maximum length from the node to the root of the tree[4]. It is available solely at the application level. A deep inheritance tree makes the understanding of the object-oriented architecture difficult. Well structured OO systems have a forest of classes rather than one large inheritance lattice. The deeper the class is within the hierarchy, the greater the number of methods it is likely to inherit, making it more complex to predict its behavior and, therefore, more fault-prone[5]. However, the deeper a particular tree is in a class, the greater potential reuse of inherited methods[4].

The rate of acquired practices (ROKR, described in above section) is another measure specific to object-oriented code, since it is computed relatively to the full number of rules, including Java-related checks. In the case of C projects only the SQuORE rules are checked, so it loses its meaning and is not generated.

# Configuration Management metrics

## Application level

We retrieve the following metrics on application artefacts:

• SCM_COMMITS: number of commits.
• SCM_COMMITS_FILES: number of files associated to commits.
• SCM_COMMITTERS: number of distinct committers.
• SCM_FIXES: number of fix-related commits, i.e. commits that include either the fix, issue, problem or error keywords in their message.

Metrics are retrieved for the overall time, the last week, last month, and last three months.

Variable names are:

• SCM_COMMITS_1W SCM_COMMITS_1M SCM_COMMITS_3M SCM_COMMITS_TOTAL
• SCM_COMMITS_FILES_1W SCM_COMMITS_FILES_1M SCM_COMMITS_FILES_3M SCM_COMMITS_FILES_TOTAL
• SCM_COMMITTERS_1W SCM_COMMITTERS_1M SCM_COMMITTERS_3M SCM_COMMITTERS_TOTAL
• SCM_FIXES_1W SCM_FIXES_1M SCM_FIXES_3M SCM_FIXES_TOTAL

## File level

We retrieve the following metrics on file artefacts:

• SCM_COMMITS: number of commits for the artefact.
• SCM_COMMITTERS: number of distinct committers for the artefact.
• SCM_FIXES: number of fix-related commits for the artefact, i.e. commits that include either the fix, issue, problem or error keywords in their message.

Metrics are retrieved for the overall time, the last week, last month, and last three months.

Variable names are:

• SCM_COMMITS_1W SCM_COMMITS_1M SCM_COMMITS_3M SCM_COMMITS_TOTAL
• SCM_COMMITTERS_1W SCM_COMMITTERS_1M SCM_COMMITTERS_3M SCM_COMMITTERS_TOTAL
• SCM_FIXES_1W SCM_FIXES_1M SCM_FIXES_3M SCM_FIXES_TOTAL

# Communication metrics

Communication metrics show an unusual part of the project: people’s activity and interactions during the elaboration of the product. Most software projects have two communication media: one targeted at the internal development of the product, for developers who actively contribute to the project by committing in the source repository, testing the product, or finding bugs (a.k.a. developers mailing list); and one targeted at end-users for general help and good use of the product (a.k.a. user mailing list).

The type of media varies across the different forges or projects: most of the time mailing lists are used, with a web interface like MHonArc or mod_mbox. In some cases, projects may use as well forums (especially for user-oriented communication) or NNTP news servers, as for the Eclipse foundation projects. The variety of media and tools makes it difficult to be extensive; however data providers can be written to map these to the common mbox format. We wrote connectors for mboxes, MHonArc, GMane and FUDForum (used by Eclipse).

We retrieve the following metrics on application artefacts:

• The number of posts (COM_DEV_VOL, COM_USR_VOL) is the total number of mails posted on the mailing list during the considered period of time. All posts are counted, regardless of their depth (i.e. new posts or answers).
• The number of distinct authors (COM_DEV_AUTH, COM_USR_AUTH) is the number of people having posted at least once on the mailing list during the considered period of time. Authors are counted once even if they posted multiple times, based on their email address.
• The number of threads (COM_DEV_SUBJ, COM_USR_SUBJ) is the number of different subjects (i.e. a question and its responses) that have been posted on the mailing list during the considered period of time. Subjects that are replies to other subjects are not counted, even if the subject text is different.
• The number of answers (COM_DEV_RESP_VOL, COM_USR_RESP_VOL) is the total number of replies to requests on the user mailing list during the considered period of time. A message is considered as an answer if it is using the Reply-to header field. The number of answers is often associated to the number of threads to compute the useful response ratio metric.
• The median time to first reply (COM_DEV_RESP_TIME_MED, COM_USR_RESP_TIME_MED) is the number of seconds between a question (first post of a thread) and the first response (second post of a thread) on the mailing list during the considered period of time.

As for configuration management metrics, we worked on temporal measures to produce measures for the last week, last month, and last three months. Communication metrics are only available at the application level.

• COM_DEV_AUTH_1M, COM_DEV_AUTH_3M, COM_DEV_AUTH_1W,
• COM_DEV_RESP_TIME_MED_1M, COM_DEV_RESP_TIME_MED_3M, COM_DEV_RESP_TIME_MED_1W,
• COM_DEV_RESP_VOL_1M, COM_DEV_RESP_VOL_3M, COM_DEV_RESP_VOL_1W,
• COM_DEV_SUBJ_1M, COM_DEV_SUBJ_3M, COM_DEV_SUBJ_1W,
• COM_DEV_VOL_1M, COM_DEV_VOL_3M, COM_DEV_VOL_1W,
• COM_USR_AUTH_1M, COM_USR_AUTH_3M, COM_USR_AUTH_1W,
• COM_USR_RESP_TIME_MED_1M, COM_USR_RESP_TIME_MED_3M, COM_USR_RESP_TIME_MED_1W,
• COM_USR_RESP_VOL_1M, COM_USR_RESP_VOL_3M, COM_USR_RESP_VOL_1W</tt>,
• COM_USR_SUBJ_1M, COM_USR_SUBJ_3M, COM_USR_SUBJ_1W,
• COM_USR_VOL_1M, COM_USR_VOL_3M, COM_USR_VOL_1W,

# References

1. Posnett, D., Filkov, V., & Devanbu, P. (2011). Ecological inference in empirical software engineering. In Proceedings of the 2011 26th IEEE/ACM International Conference on Automated Software Engineering (pp. 362–371). IEEE Computer Society. doi:10.1109/ASE.2011.6100074
2. McCabe, T. (1976). A complexity measure. Software Engineering, IEEE Transactions on, (4), 308–320.
3. Halstead., M. H. (1977). Elements of Software Science. Elsevier Science Inc.
4. 4.0 4.1 Shyam R. Chidamber, & Chris F. Kemerer. (1993). A Metrics Suite for Object Oriented Design.
5. Gustafson, D. A., & Prasad, B. (1991). Properties of software measures. In Formal Aspects of Measurement, Proceedings of the BCS-FACS Workshop on Formal Aspects of Measurement, South Bank University, London, 5 May 1991 (pp. 179–193). Springer.