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Updated documentation for updated Database design.
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[147]	1	\documentclass{article}
	2	\title{Database Connection for the CPS Facilitator Tool}
	3	\author{Jos Kraaijeveld}
	4	\date{\today}
	5	\usepackage{moreverb}
	6	\usepackage{fullpage}
	7	\usepackage{framed}
	8	\usepackage{float}
	9	\usepackage{multirow}
[160]	10	\usepackage[final]{pdfpages}
	11	\usepackage{hyperref}
[147]	12	\begin{document}
	13
	14	\maketitle
	15
	16	\pagebreak
	17
	18	\tableofcontents
	19
	20	\pagebreak
[231]	21	\section{Changelog}
	22	\textit{13-01-2012}: Fixed the issue with Open-Closed, updated documentation accordingly.
[147]	23
	24	\section{Introduction}
	25	This document describes the database design and implementation for the CPS Facilitator Tool. The goal is to make
	26	sure everyone can communicate with the RDF-based database without having to write queries. The DBInterface is
	27	written in PHP and requires slight PHP knowledge before use. It is heavily based on initial work by Bas van Nuland. \\
	28
	29	If you use this framework, you can skip to the `How to use'-part of this document (\ref{howtouse}). If you are
	30	planning to improve this framework, I recommend reading the RDF Primer\footnote{http://www.w3.org/TR/rdf-primer/} and
	31	SPARQL Query Language for RDF\footnote{http://www.w3.org/TR/rdf-sparql-query/}. A full specification of the current
	32	implementation can be found in section \ref{spec}. The areas I suggest improving upon first are described in section
	33	\ref{futurework}.
	34
	35	\section{How to use}\label{howtouse}
	36	\subsection{Initialization}
[231]	37	Before the database can be used, you should remember to import master.php on every page:
[147]	38	\begin{verbatimtab}
[231]	39	require 'classes/master.php';
[147]	40	\end{verbatimtab}
	41
	42	\subsection{Basic queries}
	43	\subsubsection{Retrieving data}
[231]	44	Getting data is done by calling the get method of the class for which you want to retrieve data. The
	45	specification for this method is the same for every class and is as follows.\\ \\
[147]	46	\begin{tabular}{\| l \|\| r \|} \hline
	47	\multicolumn{2}{\|c\|}{Function get()} \\ \hline
	48	Second argument: \$arguments & Array \\ \hline
	49	Return type: & Array/Variable \\ \hline
	50	\end{tabular} \\ \\
	51
[231]	52	The return type is an Array of objects with the type corresponding to the class you caled it on. For
	53	instance, if you call User::get() you will only get User objects. Below are a few examples showing the usage
[147]	54	of get(). A description of what arguments are possible per type is given in section \ref{arguments}.
	55
	56	\begin{figure}[H]
	57	\caption{Retrieving all questions and echo their title.}
	58	\begin{framed}
	59	\begin{verbatimtab}
[231]	60	$questions = User::get(array());
[147]	61	foreach ($questions as $question)
	62	{
	63	echo $question->title;
	64	}
	65	\end{verbatimtab}
	66	\end{framed}
	67	\end{figure}
	68
	69	\begin{figure}[H]
	70	\caption{Retrieving all surveys containing questions with IDs q1 and q2, created by the user
	71	Jos, printing all questions in those surveys}
	72	\begin{framed}
	73	\begin{verbatimtab}
	74	//To get all surveys created by the user Jos, we need his UID.
	75	//We first query the database for the User object belonging to Jos.
[231]	76	$userResults = User::get(array("name" => "Jos"));
[147]	77	//Assuming there is a result, the UID is:
	78	$josUID = $userResults[0]->uid;
	79	//Now to get the requested surveys:
[231]	80	$surveys = Survey::get(array("questions" => array("q1", "q2"),
[147]	81	"creator" => $josUID));
	82	//And to print all the questions in these surveys:
	83	foreach($surveys as $survey)
	84	{
	85	echo "All the questions in " . $survey->name;
	86	foreach($survey->questions as $question)
	87	{
	88	print_r($question);
	89	}
	90	}
	91	\end{verbatimtab}
	92	\end{framed}
	93	\end{figure}
	94
	95	\subsubsection{Storing data}
[231]	96	Storing data is easy, as long as you stick to using the given PHP Classes. Retrieve these objects by using
	97	the get() function, and call the save() function of the objects.: \\ \\
[147]	98	\begin{tabular}{\| l \|\| r \|} \hline
[231]	99	\multicolumn{2}{\|c\|}{Function save()} \\ \hline
	100	Returns: \$boolean & succeeded \\ \hline
[147]	101	\end{tabular} \\ \\
[231]	102	If the save function returns false, there is an invalid references in that object which needs to be resolved
	103	before saving. This ensures the database is always valid.
[147]	104	Another important thing to note is that currently it will overwrite a previous object with the same UID in
	105	the database. The following examples show how to create new objects and save them, as well as edit old
	106	objects and save them.
	107
	108	\begin{figure}[H]
	109	\caption{Creating a new Answer object and storing this in the database.}
	110	\begin{framed}
	111	\begin{verbatimtab}
	112	//For this example, I choose a random question to answer
[231]	113	$questions = Question::get(array());
[147]	114	$question = $questions[2];
	115	//Note two things:
	116	//1 - If you pass 'null' as first argument when creating any object
	117	// A new UID will be generated, indicating a new object.
	118	//2 - Depending on the question, there can be multiple answers
	119	// This means the values-argument (third argument) is an array.
	120	$answer = new Answer(null, $question, array("12345", "four"));
	121	//Save the answer in the database
[231]	122	if($answer->save())
	123	echo "Success";
[147]	124	\end{verbatimtab}
	125	\end{framed}
	126	\end{figure}
	127
	128	\begin{figure}[H]
	129	\caption{Getting a Survey object from the database and removing the first question. Also alter this
	130	question.}
	131	\begin{framed}
	132	\begin{verbatimtab}
	133	//Get the survey
[231]	134	$surveyResults = Survey::get(array("uid" => "b91d39e8667372e220bb861b3f94b5bd"));
[147]	135	$survey = surveyResults[0];
	136	//Remove the question
	137	$question = $survey->questions[0];
	138	unset($survey->questions[0]);
	139	//Change the question
	140	$question->title = "New Title";
	141	//Save the survey and question
[231]	142	$question->save(); $survey->save();
[147]	143	\end{verbatimtab}
	144	\end{framed}
	145	\end{figure}
	146
	147
	148	\subsection{Arguments}\label{arguments}
	149	The arguments you can supply when calling the get() function differ greatly per type. Unfortunately, there is no
	150	way around this, so here is a complete overview of arguments per type. \\
	151	\begin{tabular}{\| l \| c \| c \| l \|} \hline
[196]	152	\textbf{Type} & \textbf{Argument name} & \textbf{Argument type} & \textbf{Extra notes} \\ \hline \hline
	153	\multirow{3}{*}{Answer} & uid & String & \\
[147]	154	& question & String & UID of the question \\
[196]	155	& values & Array of Strings & \\ \hline \hline
	156	\multirow{4}{*}{AnswerSet} & uid & String & \\
[147]	157	& survey & String & UID of the Survey \\
	158	& respondent & String & UID of the Respondent \\
[196]	159	& answers & Array of Strings & UIDs of the Answers \\ \hline \hline
	160	\multirow{4}{*}{Application} & uid & String & \\
[147]	161	& title & String & \\
[196]	162	& description & String & \\
	163	& style & String & \\ \hline \hline
	164	\multirow{5}{*}{Question} & code & String & \\
[147]	165	& title & String & \\
[196]	166	& type & String & \\
	167	& description & String & \\
[147]	168	& category & String & \\
[196]	169	& definedanswers & Array of Strings & String values of possible answers \\ \hline \hline
	170	\multirow{3}{*}{Respondent/User} & uid & String & \\
	171	& name & String & \\
[147]	172	& password & String & Use hashes to store passwords \\ \hline \hline
[196]	173	\multirow{7}{*}{Session} & uid & String & \\
[147]	174	& title & String & \\
[160]	175	& creator & String & UID of the User \\
[196]	176	& creationdate & String & Unix Timestamp. No way to search on intervals (yet). \\
	177	& applications & Array of Strings & UIDs of the Applications \\
	178	& surveys & Array of Strings & UIDs of the Surveys \\
	179	& answersets & Array of Strings & UIDs of the AnswerSets \\ \hline \hline
	180	\multirow{9}{*}{SessionInstance} & uid & String & \\
[147]	181	& title & String & \\
[196]	182	& location & String & \\
	183	& facilitator & String & UID of the user that facilitated the session \\
	184	& startime & String & Unix Timestamp. No way to search on intervals (yet). \\
	185	& endtime & String & Unix Timestamp. No way to search on intervals (yet). \\
	186	& notes & Array of Strings & \\
	187	& session & String & UID of the Session this Instance refers to. \\
	188	& resultset & String & UID of the ResultSet this Instance has. \\ \hline \hline
	189	\multirow{4}{*}{Survey} & uid & String & \\
	190	& title & String & \\
	191	& description & String & \\
[147]	192	& creator & String & UID of the user that created this survey \\
[196]	193	& questions & Array of Strings & UIDs of the Questions \\ \hline \hline
[147]	194	\end{tabular} \\
	195
	196	Whenever an Array has to be supplied, it will match for results that satisfy \textit{all} the constraints given
	197	in the array.
	198
[160]	199	\section{Specification}\label{spec}
	200	\subsection{Models}
	201	The framework heavily relies on the Object Oriented Programming paradigm, and only allows you to create, edit
	202	and store data through instances of precreated classes. All these classes inherit from a global
	203	ResearchToolObject class. A UML class diagram of the model classes can be found in Appendix \ref{models}.
[189]	204	The most important thing to note is that references to other objects are not evaluated immediately. Rather,
	205	these classes with references have to override the evaluate() function, which in turn tries to query the
	206	database and resolve those UIDs to model objects. This gives us two advantages: initial queries do not scale
	207	exponentially because of the 'lazy' evaluation, and the boolean return value notifies us when there exists an
	208	incorrect reference. By evaluating before saving an object, we ensure that there cannot exist invalid values in
	209	the database.
	210
[231]	211	\subsection{Static functions, non-static functions}
	212	It is important to note that the get() function of each object is static, whilst the save() function is not.
	213	This is to provide a better saving mechanism in the future: tracking when an object gets changed and saving it
	214	automatically. The get() function is static because there is no reason for it to be linked to a specific Object,
	215	only to the type it describes as a whole.
	216
	217	\subsection{Adding to the system}
	218	Adding support for new datatypes is easy and can be done by extending the ResearchToolObject class and ensuring
	219	the get() and save() methods are implemented correctly. Simply look at the existing classes and stick to the
	220	same idea unless you want to radically change the infrastructure.
	221
[160]	222	\subsection{PHPDoc}
	223	PHPDoc for the database classes can be found at
[172]	224	\href{http://svn.tbm.tudelft.nl/TBM-CPS/RESEARCHTOOL/Doc/Backend/PHPDoc/index.html}{SVN}.
[147]	225
	226	\section{Future Work}\label{futurework}
[179]	227	\subsection{Deal with invalid or missing values}
	228	This goes in two parts. Firstly, the database now assumes that given an entry, all the fields for its type are there and
	229	filled in. This is unwanted since it can cause issues with backwards compatability of certain .rdf files. Secondly, it
[196]	230	assumes that fields containing a UID to a different entry actually point to a valid entry. For instance, a Survey evaluation will
	231	try to get a User object as its creator value from the database as well, assuming it exists. It will return false if this user object
[179]	232	does not exist.
	233
[160]	234	\appendix
	235	\pagebreak
	236	\section{Class diagram of the models}\label{models}
	237	\begin{figure}
	238	\includepdf[scale=1.22]{DBModels.pdf}
	239	\end{figure}
[147]	240
	241	\end{document}

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